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NGC 1333: A Nearby Burst of Star Formation

  • W. M. Keck Observatory

Abstract and Figures

NGC 1333 is the currently most active region of star formation in the Perseus molecular cloud. The presence of emission-line stars and Herbig-Haro objects first established NGC 1333 as an active region of star formation. Today, NGC 1333 is one of the best studied extremely young clusters of low to intermediate mass stars. This region is rich in sub-mm cores, embedded YSOs, radio continuum sources, masers, IRAS sources, SiO molecular jets, H_2 and HH shocks, molecular outflows, and the lobes of extinct outflows. Dozens of outflows from embedded and young cluster members criss-cross this region. While the complexity and confusion of sources and outflows has made it difficult to unravel the relations between various components, NGC 1333 has illuminated the roles of feedback and clustering phenomena in star formation.
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Handbook of Star Forming Regions Vol. I
Astronomical Society of the Pacific, 2008
Bo Reipurth, ed.
NGC 1333: A Nearby Burst of Star Formation
J. Walawender
University of Hawaii, Institute for Astronomy, 640 N. Aohoku Pl. Hilo, HI
96720, USA
J. Bally
University of Colorado, Center for Astrophysics and Space Astronomy, 389
UCB, Boulder, CO 80309, USA
J. Di Francesco
Herzberg Institute of Astrophysics, National Research Council of Canada,
5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
J. Jørgensen
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge,
MA 02138, USA
K. Getman
Department of Astronomy and Astrophysics, Penn State University, 525 Davey
Lab, University Park, PA 16802, USA
Abstract. NGC 1333 is the currently most active region of star formation in the
Perseus molecular cloud. The presence of emission-line stars and Herbig-Haro objects
first established NGC 1333 as an active region of star formation. Today, NGC 1333 is
one of the best studied extremely young clusters of low to intermediate mass stars. This
region is rich in sub-mm cores, embedded YSOs, radio continuum sources, masers,
IRAS sources, SiO molecular jets, H2and HH shocks, molecular outflows, and the
lobes of extinct outflows. Dozens of outflows from embedded and young cluster mem-
bers criss-cross this region. While the complexity and confusion of sources and out-
flows has made it difficult to unravel the relations between various components, NGC
1333 has illuminated the roles of feedback and clustering phenomena in star formation.
1. Overview of NGC 1333
First discovered by Eduard Sch¨onfeld in 1855, NGC 1333 (Figs. 1 & 2) is a bright
reflection nebula in the western portion of the Perseus molecular cloud. The earli-
est references to NGC 1333 in research literature are by Edwin Hubble who included
NGC 1333 in a catalog of nebulae used to examine the distribution (Hubble 1922a) and
stellar content (Hubble 1922b) of Galactic nebulae. The star BD +30549 illuminates
NGC 1333 and was found to be a B8 spectral type (van den Bergh 1966; Racine 1968).
Walawender et al.
Figure 1. A composite of visible wavelength and infrared images of NGC 1333.
Hα, S II, and iimages are from the Mosaic camera on the Mayall 4 meter telescope
at Kitt Peak (from Walawender et al. 2005). The broadband ifilter is mapped to
blue, the Hαimage is mapped to green, and the S II image is mapped to orange. The
infrared component (mapped to the red channel) is from the Spitzer Space Telescope
4.6 µm image. The Spitzer image is courtesy of the Legacy Program ”From Molec-
ular Cores to Planet Forming Disks” (NASA/JPL-Caltech & c2d LegacyTeam). The
field is approximately 35across and is oriented North up, East left.
The NGC 1333 reflection nebula and its associated dark cloud L1450 (also known
as Barnard 205) are located at the northern end of a degree-long, north-south ridge of
CO emission in the Perseus region at the west side of a large cavity in the Perseus
molecular cloud (Fig. 1 in Sargent 1979; Loren 1976). Work by Herbig & Kameswara
Rao (1972), Herbig (1974), and Liu et al. (1981) showed that NGC 1333 contains
numerous H-alpha emission line stars. Today, the term NGC 1333 is used to denote the
young stellar cluster in addition to the reflection nebula.
NGC 1333
Figure 2. Hαimage of the NGC 1333 region from Walawender et al. (2005).
Several key objects are labeled.
The molecular mass in the NGC 1333 region is approximately 450 M(Warin
et al. 1996). The molecular cloud surrounding NGC 1333 contains many cavities sur-
rounded by filaments of dense gaswhich tend to point away from the most active centers
of star formation (Lefloch et al. 1998; Quillen et al. 2005). Although there is some cor-
relation with currently active outflows, most cavities are not associated with obvious
sources. Quillen et al. (2005) interpreted the radial filaments pointing away from the
NGC 1333 cluster as the walls of ancient outflow cavities which are no longer actively
driven, and therefore do not contain Herbig-Haro objects, H2shocks, or molecular out-
Walsh et al. (2006) found evidence for pervasive infall of molecular gas onto the
NGC 1333 region. They found excess redshifted self-absorption in several transitions of
HCO+which is spatially extended over a 0.39 pc2region. They interpret this signature
as evidence for a global infall rate of ˙
M104Myr1. Currently, the NGC 1333
cluster contains about 150 young stars with a median age of about 106years and a total
Walawender et al.
mass of about 100 M. Averaged over the last million years, the star formation rate in
NGC 1333 must have been close to 104Myr1(see also Walsh et al. 2007).
There are several measurements of the distance to NGC 1333. Cernis (1990) sug-
gested a distance of 220 pc to NGC 1333 based on interstellar extinction. Herbig &
Jones (1983) adopted a distance of 350 pc to NGC 1333 based on several previous
measurements. Recently, Hirota et al. (2007) have determined a distance to NGC 1333
of 235 ±18 pc based on VLBI parallax measurements of the SVS 131source. Though
this is a measurement of a single stellar source, it is consistent with the photometric
measurements of the cluster made by Cernis (1990), therefore we consider it to be the
best value currently available, however the reader should be aware that many papers
have used and continue to use distance values of 300-350 pc.
NGC 1333 has been the target of numerous studies across the electromagnetic
spectrum. In this chapter we summarize the infrared observations (Section 2.) and de-
scribe notable observations in the radio (submillimeter through centimeter wavelengths;
Section 3.)including high resolution interferometric observations. Protostellar outflows
may have played a significant role in the evolution of star formation in NGC 1333 and
are described in Section 4. Detailed summaries of four notable objects (SVS 13/HH 7-
11, IRAS 2, IRAS 4, and HH 12) are given in Section 5. Lastly, NGC 1333 has been
the target of several studies using X-rays which are summarized in Section 6.
2. Infrared Photometric Surveys
The population of young stellar objects in the NGC 1333 region has been an obvious tar-
get for photometric surveys at near- and mid-infrared through far-infrared wavelengths.
2.1. The First Surveys (pre-1990)
The NGC 1333 cluster was first mapped at infrared wavelengths, J(1.25 µm), H
(1.6 µm), K(2.2 µm), and L(3.5 µm) by Strom et al. (1976), who identified 25 sources,
all likely YSOs. Harvey et al. (1984) presented mid/far-infrared (1 µm–100 µm) pho-
tometry of a handful of these sources using the NASA Infrared Telescope Facility
(IRTF) and Kuiper Airborne Observatory (KAO). They identified two sources with
strongly increasing SEDs from near-infrared wavelengths toward 100 µm, indicative
of their embeddedness and association with local warm dust condensations (envelopes
in the current terminology). Jennings et al. (1987) used data from the Infrared Astro-
nomical Satellite (IRAS) Chopped Photometric Channel to identify nine distinct far-
infrared sources at 50 and 100 µm. They showed that in particular two of these sources
(IRAS 1 and IRAS 4) were “protostars”, i.e., obscured by their infalling envelope of
gas and dust: the latter did not show a peak in maps of dust temperature constructed
on the basis of the emission at these two wavelengths, indicating that it was not signif-
icantly warmer than the large scale cloud. Jennings et al. (1987) also speculated that
1There is some confusion regarding the designation of this source as either SVS 13 or SSV 13. It was listed
as source number 13 by Strom et al. (1976), which led to the SVS designation. Herbig & Jones (1983),
however, chose to use SSV 13 because “the designation SVS has been pre-empted.” Subsequently both
SVS and SSV have been used in the literature when referring to this source. We choose to use the SVS
designation to match the majority of the literature, however the reader should be aware of the alternate
naming convention.
NGC 1333
IRAS 4 was binary in nature based on its association with two maser sources, some-
thing which has since then been confirmed through higher resolution mid/far-infrared
and (sub)millimeter observations (see Sections 3. and 5.3.).
2.2. After 1990; Near/Mid-IR Wavelengths
The early surveys suffered from poor resolution, a particular issue in regions such as
NGC 1333 where the source density is high. The continued development of near-
infrared ground based detectors allowed for a number of deep ground based surveys
of NGC 1333 at near-infrared (J,H, and K) wavelengths up through the 1990s and
early 2000s.
Aspin et al. (1994) mapped 10×10of the southern region of NGC 1333 using
the United Kingdom Infrared Telescope (UKIRT) and identified 134 sources complete
down to a Kmagnitude of 16.0. Cross referencing this list with that of Strom et al.
(1976), they found 13 overlapping sources. Based on near-infrared and optical color-
color diagrams (specifically JHvs. HK), Aspin et al. identified 55 likely pre-main
sequence stars from this sample along with another 14 candidates. The remainder of
the sample were likely reddened background stars. Of the possible pre-main sequence
stars, only a small group (3) showed colors consistent with Class I YSOs, about 25%
showed colors and magnitudes consistent with T-Tauri stars and the remainder were
consistent with low-mass T-Taurilike pre-main sequence stars with masses <0.2M.
A subset of this region was surveyed in L-band (3.42 µm) by Aspin & Sandell (1997)
confirming the nature of the infrared excess sources and aiding in the classification of
some of these candidates.
Lada et al. (1996) covered a somewhat larger region of NGC 1333, also at J,
H,K, but slightly shallower (completeness at Kof 14.5 magnitudes). They found
that the infrared sources in the region were non-uniformly clustered into two groups,
one centered around the reflection nebula around BD +30549 and the other around the
southern part of the cluster studied by Aspin et al. (1994). They also found that the bulk
of the stars (61%) associated with this “double cluster” showed infrared excesses, in-
dicative of these clusters being young (106years) and thereby significantly different
from the other prominent cluster in the Perseus region: IC 348 (see chapter by Herbst
in this volume). Aspin (2003) performed infrared spectroscopy of a subsample of the
sources in the southern cluster. Based on HR diagram classification of these sources and
comparison to theoretical evolutionary tracks, it was suggested that the ages of young
stars in NGC 1333 covered a wide range from a few×105years up to sources close to
the Zero Age Main Sequence at 5×107years.
A deep J,H, and Ksurvey (to a Kmagnitude of 16) of the northern cluster was
performed by Wilking et al. (2004). From the near-infrared colors of the objects based
on this survey, they identified 25 brown dwarf candidates. These sources were targets
for follow-up observations using low resolution near-infrared spectroscopy to spectrally
confirm the very low-mass nature of these sources.
Greissl et al. (2007) examined the core of the NGC 1333 cluster using NICMOS
on HST and determined the IMF of the cluster to be consistent with a field IMF.
2.3. Spitzer and Beyond
As a prelude to the Spitzer observations, Rebull et al. (2003) surveyed a small number
of the more embedded objects in N(10.8 µm) and Q(17.9 µm) using the MIRLIN
camera on the Palomar 5 m telescope and the NASA IRTF. They detected eight sources
Walawender et al.
at these wavelengths and, together with SEDs compiled from the literature, classified
them according to their embedded nature.
The NGC 1333 region was surveyed with the Spitzer Space Telescope, under a
number of programs including the “Cores to Disks” legacy project (as part of Perseus;
see Jørgensen et al. 2005b and Rebull et al. 2007) and the GTO Spitzer Young Clus-
ter Survey. From these combined data, Gutermuth et al. (2008) found 137 members
associated with NGC 1333 itself, 39 protostars and 98 pre-main sequence stars with
disks. Class I objects were found to have a spatial distribution similar to that of dense
gas found in the region, as traced by Sandell & Knee (2001), while Class II objects
accounted for the “double-cluster” morphology seen by Lada et al. (1996). The two
density peaks of this morphology are anticorrelated with locations of dense gas. De-
spite this difference, the nearest-neighbor distance distributions of both classes each
peak at 0.045 pc, suggesting the Class II population is both very young and has a low
overall velocity distribution. They further argue that the cavities in the center of NGC
1333 were thus dispersed by the Class II populations and not by outflows. Overall,
NGC 1333 was revealed to have a roughly uniform density distribution within a 0.3 pc
radius, and a steep decline at larger radii, possibly reflecting original cloud structure.
Relative to the IC 348 cluster (also in Perseus but at the opposite end of the cloud),
NGC 1333 shows a larger fraction of Class I objects vs. Class II objects, suggesting
a significant age difference between these clusters. Indeed, NGC 1333 may be more
similar in age to the smaller, very young groups in Perseus, e.g., L1448, L1455, or B1.
Interestingly, before Spitzer, a small fraction of the deeply embedded protostars
in the region were known to have mid-infrared counterparts, but the high sensitivity
and high angular resolution of the Spitzer observations identified a number of these
sources at wavelengths as short as 3.6 µm, making it possible to characterize them.
To establish a relatively unbiased sample of such sources, Jørgensen et al. (2007b)
combined surveys by Spitzer and the Submillimetre Common-User Bolometer Array
(SCUBA) at the James Clerk Maxwell Telescope (JCMT) and studied the separation
between the mid-IR sources and the SCUBA clumps and the characteristics of both
(see Fig. 3). About half of the dust condensations in NGC 1333 were found to have
associated mid-infrared sources and these cores were forming stars with an efficiency
of 1015% (not including the efficiency of forming the cores in the first place), similar
to what is observed in the larger scale cloud.
3. Submillimeter, Millimeter & Radio Observations of NGC 1333
NGC 1333 has long been known to harbor many embedded protostars. In particular,
its southern half contains many bright Class 0/I objects, including SVS 13, IRAS 2,
IRAS 4 and their individual components, which have been closely observed over the
last twenty years.
In this section, we describe notable continuum observations made at submillimeter
through centimeter wavelengths of these objects and their dense environments. Such
observations are sensitive to high column density dust associated with embedded pro-
tostars. A general trend seen from such data has been that observations of increased
sensitivity, map extent or resolution have revealed new embedded objects in the re-
gion. Identifications of objects, especially at the lower brightness ends of samples, can
be biased depending on the method used (e.g., by eye or CLUMPFIND), leading to
differences between object lists found in different studies.
NGC 1333
Figure 3. Comparison between Spitzer IRAC image (Jørgensen et al. 2005b;
Gutermuth et al. 2008) and SCUBA 850 µm (contours; Sandell & Knee 2001; Kirk
et al. 2006). For further details about the comparison across these wavelengths see
Jørgensen et al. (2007b) and Gutermuth et al. (2008).
3.1. Single-Dish Observations
Early surveys with single element bolometers targeted individual known protostars in
the NGC 1333 region (e.g., Sandell et al. 1990, 1991, 1994), but with bolometer ar-
rays in the late nineties it became possible to map larger (&10 square arcminute sized)
The higher angular resolution provided by large single-dish submillimeter tele-
scopes made it possible to explore the dust envelopes of the IRAS objects and in some
cases resolve them into multiple sources. For example, Sandell et al. (1990) and Sandell
et al. (1994) observed SVS 13 and IRAS 2 with the UKT14 bolometer system on the
JCMT at 1.1 mm, 800 µm, or 450 µm respectively (with respective resolutions of 19′′,
14′′, and 8.5′′ FWHM), revealing extended continuum emission associated with each
Walawender et al.
source, but no definitively identified new objects. Sandell et al. (1991), however, ob-
served IRAS 4 and resolved it into two objects, 4A and 4B, with a 30′′ separation
oriented NW-SE. A third object, 4C, was seen in these images at a position 50′′ NE
of 4A, but its existence was only confirmed later by the VLA data of Rodr´ıguez et al.
(1999) and the SCUBA data of Smith et al. (2000).
Lefloch et al. (1998) mapped the southern region of NGC 1333 at 1.3 mm using
the IRAM 30 m telescope (11′′ resolution): they detected six dust peaks in the region,
four associated with protostars, SVS 13, IRAS 2, IRAS 4A and IRAS 4B. They further-
more identified two cavities in the region, coinciding with similar cavities from line
observations (e.g., Warin et al. 1996). They suggested that these cavities were related
to the action of the outflows from the newly formed stars.
Bolometric arrays at single-dish millimeter/submillimeter telescopes allowed wider
fields in star forming regions to be surveyed at high sensitivity and resolution, reducing
the biases of earlier studies that forced observations toward previously identified ob-
jects. Figure 4 shows an 850 µm continuum map made from data obtained by Sandell
& Knee (2001) with SCUBA on the JCMT, covering a 13×18region centered near
SVS 13. Sandell & Knee (2001) observed both 850 and 450 µm at 14′′ and 9′′ FWHM
resolution respectively. These maps revealed further multiplicity in some sources, they
resolved IRAS 2 into three objects, 2A, 2B and 2C, with 30′′ separation oriented
NW-SE. They identified 33 submillimeter sources associated with NGC 1333. They
also pointed toward the importance of outflows for the distribution of the matter in
NGC 1333, suggesting that triggered star formation is a common mode there. IRAS
4A was found to be the brightest object at 850 µm with a flux of 9 Jy, or 3×that of
the next brightest objects, SVS 13, 4B, and 2A. Such maps revealed even more embed-
ded objects within NGC 1333.
Chini et al. (1997) resolved SVS 13 into three sources, MMS 1, MMS 2 and MMS
3 (later identified as SVS 13, 13B and 13C2), with 15′′ separation oriented NE-SW.In
addition, these maps revealed dust ridges or filaments bordering on possible cavities in
the central part of the region, e.g., see Lefloch et al. (1998). More recently, NGC 1333
has been included in larger-scale continuum maps of the inner regions of the Perseus
cloud, e.g., at 850 µm with the JCMT by Hatchell et al. (2005) and Kirk et al. (2006)
(see also Ridge et al. 2006) and at 1.3 mm with the CSO by Enoch et al. 2006 at 31′′
FWHM resolution.
3.2. Interferometric Observations
Embedded objects in NGC 1333 identified in single-dish maps have been observed at
higher resolution using various interferometers to improve understanding of the small-
scale structure of their dust envelopes and circumstellar disks and to look for further
multiplicity. A significant number of the deeply embedded objects were targeted by
Looney et al. (2000) in their large subarcsecond millimeter wavelength interferometric
survey, revealing the multiplicity of many of these deeply embedded sources on arcsec-
ond scales. A number of the embedded sources in NGC 1333 have also been the target
of continuum surveys at longer (centimeter) wavelengths.
Rodr´ıguez et al. (1999) surveyed an 8×8region centered on SVS 13 using the
Very Large Array (VLA) at 3.6 cm and 6 cm at 4′′-5′′ FWHM resolution, detecting
2SVS 13 is coincident with VLA 2, a radio continuum source identified by Haschick et al. (1980),
Rodr´ıguez & Canto (1983), and Snell & Bally (1986) as corresponding to the water maser H2O(B).
NGC 1333
Figure 4. A map of 850 µm continuum emission from NGC 1333, as observed
with SCUBA by Sandell & Knee (2001). The grey scale extends from 0.005 to 1.0
Jy beam1. The resolution is 14′′ FWHM. Triangles denote the peak positions of
the 33 objects identified by eye by Sandell & Knee. Stars denote the positions of
HH 12 IR (VLA 42), SVS 3, and BD+30459, each associated with submillimeter
continuum emission.
44 sources of which 26 were believed to be associated with young stellar objects in
NGC 1333. Reipurth et al. (2002) followed up on those observations with deep, higher
resolution images of a number of some of the deeply embedded outflow sources in
the region. These surveys identified most of the known far-infrared and submillimeter
components of the embedded protostars at these long wavelengths. For most of the
sources this was attributed to the action of thermal jets on small scales - although a
few sources, including the two components in the IRAS 2 binary, showed evidence
Walawender et al.
for continuum from thermal dust emission extending from submillimeter to these long
wavelengths (see also Fig. 5 of Jørgensen et al. 2005a).
Detailed discussions of the interferometric observations of the SVS 13, IRAS 2
and IRAS 4 source regions can be found in Sections 5.1., 5.2., and 5.3., respectively.
4. Protostellar Outflows
The large number and area covering factor of shock excited Herbig-Haro objects (see
Fig. 5) and near-infrared H2emission associated with dozens of overlapping outflows
distinguishes NGC 1333 from other nearby star forming regions. Figure 6 shows the
Spitzer IRAC 4.6 µm image of the NGC 1333 region. The cluster and the 1 degree-
long ridge of molecular cloud extending south are covered with filaments, bow shocks,
and irregular clumps of H2emission. Near the central part of NGC 1333, the covering
factor of shock-excited H2emission and Herbig-Haro objects is greater than 50% at
low flux levels.
Figure 5. Hαimage from the survey of Walawender et al. (2005) of the southern
half of NGC 1333.
Bally et al. (1996) found over 30 groups of HH objects associated with over a
dozen and perhaps many more currently active outflows. They describe the region as a
“microburst of star formation” of duration less than 1 Myr within a radius of less than
1 pc.
NGC 1333
Figure 6. NGC 1333 as imaged by Spitzer IRAC in band 2 at 4.5 µm showing the
same field as in Fig. 2 (Courtesy the c2dteam).
First noted by Herbig (1974) on photographic plates, the objects HH 5, 6, 7-11,
and 12 are the brightest HH objects in the region. HH 5 and 6 are relatively compact
clusters of bright knots. HH 7-11 is a chain of very bright shocks propagating southwest
from the general vicinity of SVS 13 (to be discussed in more detail in Section 5.1.).
HH 12 (see Section 5.4.) is a complex shock structure located north of HH 7-11 at the
northern end of a complex of H2filaments which line the walls of a roughly 5long
conical cavity in the NGC 1333 cloud. The HH 7-11 cavity is evident in deep I-band
and infrared images, and in sub-millimeter dust continuum and molecular line maps.
At least two jets are aimed (in projection against the plane of the sky) towards
HH 12; the northern lobe of the IRAS 2 molecular jet, and the molecular jet emerging
towards the north from the cluster of sources associated with SVS 13 located at the base
of the HH 7-11 flow (e.g. Knee & Sandell 2000). The northern tip of HH 12 is further
confused by alow-excitation ([SII] and H2dominated) outflow emerging from IRAS 6
Walawender et al.
towards PA 300. Thus, the HH 12 shock complex may be driven by any of several
Bally & Reipurth (2001) found several remarkable jets and bent Herbig-Haro out-
flows in the vicinity of NGC 1333. The several arcminute-long HH 333, located north
of the brightest portion of the reflection nebula, is one of the most collimated HH flows
known. This roughly east-west oriented jet emerges from an 18th magnitude (i-band)
star whose circumstellar disk casts a faint shadow about 10′′ in extent on surrounding
dust. This feature is oriented orthogonal to the jet axis. The jet consists of a chain of
knots connected by a faint filament of Hαand S II emission less than 2′′ wide. It is
bipolar (visible on both sides of the source) and is over 3long. It exhibits a gentle
S-shaped bend indicating that over the dynamical age ofthe most distant shocks, the jet
orientation has changed by about 10to 15.
The regions north and west of HH12 contain some remarkable C-symmetric, bent
jets emerging from visible stars (Fig. 7). C-symmetric flows include HH 334, 498, and
499. While HH 334 shows only a mild bend, HH 498 and 499 show bends ranging
from 40to over 90. While the C-symmetric outflows in the Orion nebula consistently
bend away from the nebular core, in NGC 1333 C-symmetric flows bend toward the
cluster core. A relative motion of order 10 km s1is needed to explain the degree of
jet bending observed. Such a large velocity is not likely to be produced by gas infalling
toward the cluster core. Bally & Reipurth (2001) postulated that, in Orion, jets are bent
by a wind flowing away from the nebular core while in NGC 1333 the bends are more
readily explained as being caused by the motion of the star with respect to the surround-
ing cloud. They postulated that the source stars of the bent jets in NGC 1333 have been
recently expelled from the cluster core by dynamical interactions. This scenario is con-
sistent with the relatively low obscuration toward the jet sources, as little circumstellar
material is expected to survive the acceleration of the star in such an interaction.
An S-shaped outflow, HH 343, was discovered by Bally et al. (1996) in the south-
ern part of NGC 1333, about 10south of the main cluster. Hodapp et al. (2005) ex-
amined this outflow and its source in detail using near-IR, optical, and submillimeter
imaging and near-IR spectroscopy. Proper motions of the Hαand S II knots showed
some of the shocks moving at more than 100 km s1. The shape of the outflow indi-
cates that the source has precessed by almost 90over its 6000 yr dynamical age. The
spectroscopy and submillimeter data of Hodapp et al. (2005) indicated that the source
is in a Class 0 or I evolutionary state.
The Hαemission line star SVS 20, located about 10west of the south-eastern
tip of the HH 7-11 flow and east-southeast of SVS 13, drives an unusual outflow,
HH 345/346, towards PA 220. Although this flow is collimated on scales of several
arcminutes, it isonly poorly collimated within the inner 10′′ of SVS 20. Hαimages ob-
tained between 1997 and 2001 show the emergence of a high velocity (>300 km s1)
bubble or bow shock with an opening angle of more than about 30as seen from the
star. The Herbig-Haro object HH 15 lies on the axis of the SVS 20 outflow about 9
southwest of the star. However, HH 15 also lies on the suspected axis of the IRAS 1
outflow which powers HH 338/339.
An extensive complex of HH objects can be seen south and southwest of IRAS 2
(see Section 5.2.) and IRAS 4A (see Section 5.3.). These shocks consist of HH 344,
342, 341 and the various components of HH 13 (see Bally et al. 1996, Fig. 2a). Both
the IRAS 4A and IRAS 2B jets point in this general direction. As discussed below, both
ground-based imaging and Spitzer reveal many additional shocks farther southwest.
NGC 1333
Figure 7. An Hα+ S II image of the HH 334, 498, and 499 bent jets. Image from
Walawender et al. (2005).
The infrared source IRAS 7 is located near the bright object HH 6 (displaced and
elongated to the northeast of the IR source). Ground based and Spitzer images show
a parsec-scale chain of shock-excited H2features extending towards the northwest and
southeast (PA 340/160). Evidently, IRAS 7 is the source of a quadrupolar outflow
and may therefore be a multiple star system.
Walawender et al. (2005) reported several new HH objects and jets well outside
the cluster core, at the periphery of the NGC 1333 reflection nebula, and beyond the
projected edge of the molecular cloud where confusion is not as significant as in the
cluster core. At least two large, parsec-scale flows erupt from the region. The first
contains the faint shocks HH 752, 756, and 760 tracing a NW-SE flow located near the
north end of the NGC 1333 reflection nebula. The second parsec-scale flow emerges
from the NGC 1333 cloud a few arcminutes south of HH 7-11, propagates due east for
at least 10into the degree-scale cavity between NGC1333 andBarnard 1, andconsists
of HH 348, 349, HH 766, and 767.
Sandell & Knee (2001) found that outflows play an important role in the energy
balance of NGC 1333. NGC 1333 has a filamentary cloud structure, consisting ofmany
cavities, some of which can be traced to the action of current outflows and some which
may be the remnants of past outflow activity. Knee & Sandell (2000) also estimate the
momentum and energy injection by outflows in NGC 1333 (using an estimated age of
an outflow of 0.1 Myr determined by Bally et al. 1996) to be ˙
P10 Mkm s1
and L0.1 L, enough to disrupt the cloud if these rates hold for a typical cloud
lifetime of 10 Myr. Sandell & Knee (2001) find evidence that star formation activity
may be triggered in density enhancements at the periphery of these cavities. Thus
Walawender et al.
star formation may be triggered by previous episodes of star formation and associated
outflow activity.
5. Individual Objects of Particular Interest
5.1. The SVS 13 Subcluster and HH 7-11 Outflow
First discovered by Herbig (1974), the HH 7-11 group (Fig. 8) traces a collimated
flow emerging from a dense cloud core at roughly PA 125and originates from
the vicinity of an embedded near-IR source, SVS 13 (Strom et al. 1974, 1976), which
is also coincident with H2O maser emission (Dickinson et al. 1974). Haschick et al.
(1980) resolved the H2O maser into 3 components (H2O(A), H2O(B), and H2O(C)), of
which H2O(A) coincides with the SVS 13 protostar. Grossman et al. (1987), using the
3-element Owens Valley Radio Observatory (OVRO) millimeter array at 2.7 mm and
9′′ FWHM resolution, first resolved SVS 13 into SVS 13 and 13B (see also Woody
et al. 1989).
Figure 8. Hαimage of HH 7-11 from the survey of Walawender et al. (2005). HH
objects and nearby protostars are labeled.
Proper motions of the HH knots were measured by Herbig & Jones (1983). While
the motions of HH 7-10 were not well defined, HH 11 was found to be moving at 58
km s1away from the position of SVS 13. Herbig & Jones (1983) also used the radial
NGC 1333
velocity of HH 11 to determine that the flowhas an inclination angle of 158, indicating
that we see it nearly end on.
Detection of H2from HH 7-11 was made by Simon & Joyce (1983), who found
the H2peak coincident with HH 7. Subsequent studies found additional H2emission
(Zealey et al. 1984; Lightfoot & Glencross 1986; Stapelfeldt et al. 1991; Garden et al.
1990; Aspin et al. 1994; Hodapp & Ladd 1995). Garden et al. (1990) detected awestern
(redshifted) jet in H2and found that its axis is offset north of the eastern flow axis by
about 25′′, consistent with the morphology of the CO outflow lobes.
The CO outflow corresponding to HH 7-11 was first studied by Snell & Edwards
(1981) and Edwards & Snell (1983). Liseau et al. (1988) found that the blueshifted
(eastern) lobe contains knots, while the redshifted lobe is more extended. HCO+ob-
servations by Rudolph & Welch (1988) and Dent et al. (1993) found clumps coincident
with the HH knots. This flow is one of the few which has been detected and mapped in
the 21 cm line of HI (Lizano et al. 1988; Rodr´ıguez et al. 1990).
Eisl¨offel et al. (1991) discovered that SVS 13 underwent an outburst between De-
cember 1988 and September 1990 as evidenced by a 2.5 magnitude brightening. The
brightening was observed at optical and near-IR wavelengths and tended to decrease
with increasing wavelength out to N-band. Eisl¨offel et al. (1991) found that the pho-
tometry and spectroscopy of the source suggest that SVS 13 underwent an EXor type
outburst. Further monitoring from October 1990 to December 1993 by Aspin &Sandell
(1994) showed smaller brightness fluctuations and support the conclusion of an EXor
The region was found to be even more complex with the detection of additional
nearby sources. High-resolution VLA observations of SVS 13 at 3.6 cm by Rodr´ıguez
et al. (1997) at 0.3′′ FWHM resolution, detected three further objects: VLA 3, located
6′′ WSW of SVS 13, and VLA 2(a) and 2(b), oriented NNE-SSW with a 1.5′′ separation
and later found to be coincident with SVS 13C. The SVS 13 group was further imaged
at 3.5 mm and 1.3 mm by Bachiller et al. (1998) at 4.1′′ ×3.0′′ FWHM and 1.9′′ ×
1.2′′ FWHM resolutions respectively with the IRAM Plateau de Bure Interferometer.
In these data, VLA 3 was not detected as a distinct object at either wavelength, and 13C
was only detected at 3.5 mm. Sandell & Knee (2001), however, detected 450 and 850
µm emission from the 13C location, suggesting little compact emission is associated
with that object.
The radio studies of Rodr´ıguez et al. (1999) show that the SVS13 region contains
a 3long chain of over a dozen radio continuum sources which are embedded in a ridge
of dense molecular gas and sub-mm cores extending along PA 20(Hatchell et al.
2005). The 40′′ long dense core containing SVS 13 (VLA 4) includes VLA 20, VLA 3,
VLA 17 (also known as SVS 13B), and VLA 2 (H2O(B), see Fig. 8). In addition,
Rodr´ıguez (1999) showed that SVS 13 is a binary with a separation of 0.3′′ (65 AU).
Thus, it is perhaps not surprising that multiple outflows originate from this region. For
example, the Class 0 protostar SVS 13B is known to drive a highly collimated molecular
outflow along a roughly north-south direction (PA 170; Bachiller et al. 1998).
Looney et al. (2000) observed SVS 13 at 2.7 mm and 0.5′′ FWHM resolution,
resolving SVS 13 into four components 13A1, 13A2 (VLA 3), 13B and 13C (VLA 2).
Finally, very high resolution VLA observations of SVS 13 by Anglada et al. (2000)
and Anglada et al. (2004) at 3.6 cm and 0.20′′ ×0.18′′ FWHM resolution and at 7 mm
and 0.18′′ ×0.16′′ FWHM resolution resolved SVS 13 (VLA 4) into two components,
VLA 4A and VLA 4B, separated by 0.3′′ oriented E-W. In the latter study, however,
Walawender et al.
Anglada et al. (2004) argued, using the spectral indices measured between 3.6 cm and
7 mm, that only VLA 4B emits thermal radiation from dust.
Rodr´ıguez et al. (1997) suggested that VLA 3, which lies 6′′ southwest of SVS 13
(VLA 4), is the driving source of the HH 7-11 outflow based on the alignment of the
apparent flow axis and the source’s elongation along that same position angle. Knee &
Sandell (2000) and Bachiller et al. (2000), however, found that high resolution CO ob-
servations showed that the CO lobes align well with SVS 13and not VLA 3, confirming
that SVS 13 is indeed the source of the HH 7-11 outflow. Knee & Sandell (2000) also
found the same offset in the red- and blue-shifted lobes as had been seen in the H2jet.
Neufeld et al. (2006) used Spitzer to map HH 7-11 in the 5.2-37 µm regime, mapping
emission from the S(0)-S(7) rotational lines of H2and from NeII, SiII, S, and FeII.
Bergin et al. (2003) found evidence of H2O emission excited by shocks in the HH 7-11,
IRAS 2, IRAS 4, and IRAS 7 outflows.
Near-IR images show clear evidence of multiple outflows emerging from the dense
sub-cluster of sources embedded in the cloud core associated with SVS 13 (Hodapp &
Ladd 1995). A highly collimated H2jet emerges towards the south (PA 170) from
the vicinity of SVS 13B (VLA 17). The counterflow (towards the north) is aimed
towards the large and bright shock complex HH 12 located several arcminutes north.
A second H2jet aimed to the south appears to emerge from the vicinity of VLA 2
(H2O(B)). The CO maps of Knee & Sandell (2000) provide supporting evidence for
the interpretation that HH 12 is, at least in part, powered by the outflow from VLA 17
(as discussed in Section 5.4., one of the bipolar outflows emerging from the binary
source IRAS 2A is also pumping energy and momentum towards HH 12).
Noriega-Crespo et al. (2002) imaged the HH 7-11 system using NICMOS onHST.
They found a short (1.24′′) H2jet emerging to the South of the SVS 13 source. Smith
et al. (2003) use H2imaging and shock models to conclude that the HH 7 bow shock is
a C-type shock with a speed of 55 km s1. The relatively low speed is consistent with
the proper motion measurements by Khanzadyan et al. (2003).
5.2. NGC 1333 IRAS 2
IRAS 2 was first identified as a candidate young star by Strom et al. (1976), who as-
sociated it with the visible star BD +30547 (later found to be incorrect, see Fig. 5).
Jennings et al. (1987) detected infrared emission from this source in IRAS maps. The
source was detected in the near-IR by Aspin et al. (1994) who also catalogued several
candidate H2shocks in the area.
Blake (1996) first mentioned two sources associated with IRAS 2, called 2A and
2B, from undescribed 2.7 mm observations, as two cores separated by 32′′ in the
NW-SE direction. Looney et al. (2000) also observed IRAS 2 at 2.7 mm at the same
high resolution as their observations of SVS 13, also resolving it into 2A and 2B, and
finding no new components. Using submillimeter observations, Sandell & Knee (2001)
resolved IRAS 2 into three distinct components (IRAS 2A, B, and C).
Very high angular resolution VLA observations of 2A and 2B by Reipurth et al.
(2002) (see Fig. 9) at 3.6 cm and 0.30′′ ×0.27′′ FWHM resolution detected constant
emission from each over four days. Although again 2C was not detected, variable emis-
sion was detected from VLA 9 (i.e., see Rodr´ıguez et al. 1999) located 4′′ NW of 2B
and coincident with the foreground star BD+30547. Jørgensen et al. (2004) detected
2A and 2B at 3 mm with the OVRO (3.2′′ ×2.8′′ FWHM resolution) and BIMA (6.1′′
×5.0′′ FWHM resolution) arrays. They specifically mentioned not detecting 2C, in-
NGC 1333
dicating it is not centrally concentrated and likely has not formed a protostar. Further
high resolution continuum data of 2A were obtained with the SMA by Jørgensen et al.
(2005a) at 850 µm and 1.8′′ ×1.0′′ FWHM resolution, and by Jørgensen et al. (2007b)
at 1.3 mm and 2.5′′ ×1.2′′ FWHM resolution and at 850 µm and 1.5′′ ×0.71′′ FWHM
resolution. In these studies of 2A, its inner envelope and disk were probed and no
further multiplicity was seen.
Figure 9. VLA map of the IRAS 2 region from Reipurth et al. (2002).
The first discovery of an outflow from IRAS 2 was by Liseau et al. (1988) using
CO observations. More detailed observations by Sandell et al. (1994) detected IRAS 2
in the submillimeter and found 2 CO outflows: a larger, north-south flow (PA 25)
whose redshifted lobe merges with the red lobe from SVS 13 and an east-west outflow
(PA 104) which is highly collimated and also seen in their CS maps.
Hodapp & Ladd (1995) identified a well collimated outflow in their H2observa-
tions corresponding to the north-south CO outflow, the brightest components of which
were seen by Aspin et al. (1994). They also found H2shocks which they associate
with the east-west outflow. Bachiller et al. (1998) found methanol associated with the
outflow lobes of the north-south outflow. High resolution interferometric observations
resolved the methanol emission into two knotty, highly collimated, jet-like structures.
Knee & Sandell (2000) used CO observations to associate the north-south outflow
with the IRAS 2C source. Thier North-South outflow coincides with the H2jet of
Hodapp & Ladd (1995). The position angles of the H2and CO differ by 14, perhaps
indicating precession of the source. Knee & Sandell (2000) also detected blueshifted
emission near IRAS 2B, but it could also be an overlapping outflow lobe.
Walawender et al.
Jørgensen et al. (2004) detected the east-west outflow in SiO and CO and asso-
ciated it with IRAS 2A. They also found a north-south velocity gradient which may
indicate that the north-south outflow is driven by an unresolved companion of IRAS 2A
and not by IRAS 2C as suggested by Sandell & Knee (2001). Wakelam et al. (2005)
observed IRAS 2A region in SO, SO2, and CS emission and examined the chemical
properties of the east-west outflow.
5.3. NGC 1333 IRAS 4
This source was first identified by its H2O maser emission detected by Haschick et al.
(1980) who designated it source H2O(C). Jennings et al. (1987) detected the source in
IRAS maps, designating it IRAS 4. Submillimeter observations by Sandell et al. (1991)
resolved IRAS 4 into two sources, IRAS 4A with a mass of 9.2 Mand IRAS 4B
with a mass of 4.0 M. Liseau et al. (1988) found high velocity CO associated with
this source.
After the detection of multiplicity by Sandell et al. (1991), 4A and 4B were imaged
by Mundy et al. (1993) with the VLA at 1.3, 2.0, and 3.6 cm, at 0.6′′, 0.4′′ and 0.5-1′′
FWHM resolutions respectively, detecting 4A in all three bands but 4B only at 1.3 cm.
In these images, the 1.3 cm emission associated with each object is centrally peaked
likely due to a disk component, but it also appears extended, likely due to contributions
from partially resolved envelopes. Later, fringes detected by Lay et al. (1995) at 840 µm
with the JCMT-CSO interferometer (0.5′′ FWHM resolution) revealed IRAS 4A to be
a binary itself with a 1.8′′ projected separation oriented NW-SE, and 4B to contain >2
components. Looney et al. (2000), observing 4A and 4B in 2.7 mm observations similar
to their data for SVS 13 and IRAS 2, were the first to image specifically 4A1 as well
as 4B2 located 10′′ E of 4B (now 4B1)3. At the highest resolutions, the Looney et al.
(2000) images of 4B1 show suggestions of further multiplicity, though these have not
been seen in other, similarly high resolution images. Millimeter continuum emission
from IRAS 4 was further observed interferometrically (but at lower resolution than
Looney et al. 2000) by Choi et al. (1999) with the BIMA array at 3.4 mm and 12.2′′
×7.8′′ FWHM resolution, Choi (2001) with the BIMA array at 3.4 mm and 4.6′′ ×
3.7′′ FWHM resolution, Di Francesco et al. (2001) with the IRAM PdBI at 3.2 mm
and 2.9′′ ×2.6′′ FWHM resolution and 1.3 mm at 2.0′′ ×1.7′′ FWHM resolution,
Choi et al. (2004) with the NMA at 2.1 mm and 3.7′′ ×3.0′′ FWHM resolution and
2.5′′ ×1.8′′ FWHM resolution, and Jørgensen et al. (2007a) with the SMA at 1.3 mm
and 2.5′′ ×1.1′′ FWHM resolution and at 850 µm with 1.5-1.7′′ ×1.0-0.7′′ FWHM
resolution. Also, centimeter continuum emission of IRAS 4 was observed with the
VLA by Reipurth et al. (2002) at 3.6 cm and 0.30′′ ×0.27′′ FWHM resolution, where
4A1, 4A2, 4B1 and 4C were detected but not 4B2 or any other source near 4B1 (see Fig.
10). Choi et al. (1999) and Di Francesco et al. (2001) saw evidence of infall towards
IRAS 4 from the ”inverse P-Cygni” profiles of interferometrically observed HCN 1-0
(4A), CS 3-2 (4A), and H2CO 312-211 (4A and 4B) line emission. Belloche et al. (2006)
examined IRAS 4Ausing theVLAand found signatures of collapse and very high mass
3The object 4B2 is called 4C by Choi et al. (1999) and Looney et al. (2000) but that name is given to the
third IRAS 4 source detected by Sandell et al. (1991); Rodr´ıguez et al. (1999); Smith et al. (2000); Sandell
& Knee (2001). Instead, Sandell & Knee (2001) called this object “4BE,” Smith et al. (2000) called it
“4BII,” and Di Francesco et al. (2001) called it “4B’.”
NGC 1333
infall rate of 0.72.0×104Myr1. Based on model fitting they conclude that the
collapse is induced by external compression.
Figure 10. VLA map of the IRAS 4 region from Reipurth et al. (2002).
Near-IR observations by Garden et al. (1990), Aspin et al. (1994), and Hodapp &
Ladd (1995) found a “V-shaped” filament of H2emission south of IRAS 4. Hodapp &
Ladd (1995) associated this feature’s western limb with SVS 13 flow. The eastern limb
points toward IRAS 4A. In addition, they found shocks located along the same line on
the opposite side of IRAS 4A. Some of the near-IR shocks correspond to Hαand S II
shocks seen by Bally et al. (1996).
Blake et al. (1995) presented a detailed analysis of the IRAS 4 source. This
hierarchical proto-multiple system launches a highly collimated CO outflow with a
blueshifted lobe aimed towards the southwest at PA 210. The IRAS 4A binary
produces at least two outflows visible as highly collimated SiO molecular jets (Choi
2005). The northeastern lobe of the larger, highly collimated northeast-southwest ori-
ented jet is deflected by an intervening cloud core. Rodr´ıguez et al. (1999) found cen-
timeter wavelength sources corresponding to IRAS 4A, B, and C (VLA 25, 28, and 29
Choi et al. (2006) observed the IRAS 4 region in H2(2.12 µm) and compared
those images with SiO observations. They found that the northeast-southwest flow may
be drifting or precessing clockwise at 0.011yr1.
Park & Choi (2007) observed H2O maser emission around IRAS 4 at an angular
resolution of about 0.08 arcseconds and found masers grouped around the IRAS 4A and
Walawender et al.
4B sources. Six of the sources are within 100 AU of IRAS 4A2 and they conclude that
the masers are part of a circumstellar disk. No masers were detected around IRAS 4A1.
Four maser spots were detected around the IRAS 4B1 source linearly distributed along
the flow axis. More recently, Marvel et al. (2008) used multi-epoch VLBA observa-
tions to measure accurate proper motions of the water maser clusters within 100 AU of
IRAS 4A2 and IRAS 4BW. For both sources there are two groups of masers that move
away from each other at more than 50 km s1. The directions of the proper motion
vectors suggest that both IRAS 4A2 and 4BW may have further companions.
5.4. HH 12
HH 12 is a large bright Hαand S II shock which lies 4.5northwest of HH 7-11 (see
Fig. 5). Proper motions by Herbig & Jones (1983) indicate that this shock is moving
to the north. Subsequent authors have suggested candidate sources to the south, e.g.,
SVS 11 (Herbig & Jones 1983), SVS 10 (Cohen & Schwartz 1983), SVS 9 (Cohen
& Schwartz 1983), or other optically visible stars (Strom et al. 1983). HH 12 lies
immediately to the west of SVS 12 leading to suggestions that SVS 12 is driving a
wide angle wind (Simon & Joyce 1983; Stapelfeldt et al. 1991; Garden et al. 1990).
Bally et al. (1996) suggested that HH 12 may be a superposition of shock systems.
Bachiller et al. (1998) found an SiO jet emanating from SVS 13B near HH 7-11.
This jet points toward PA 160, roughly away from HH 12. The redshifted component
of this jet is much fainter with one peak position symmetrically about SVS 13B. Some
of the H2features of Hodapp & Ladd (1995) coincide with the jet. Knee & Sandell
(2000) found a CO jet coinciding with the SiO jet. Their northern component was
mildly blueshifted, but they suggest that redshifted emission would be confused in this
area making detection of thenorthern component of the outflow lobe difficult to detect.
The radial velocities of HH 12 are blueshifted, while the northern SiO jet from
SVS 13B appears to be only slightly redshifted and the northern CO component slightly
blueshifted. This could be due to redirection of the jet, or turbulent mixing, since the
inclination angle of the outflow is 14based on the proper motions of Herbig & Jones
6. X-rays from NGC 1333
The NGC 1333 region was observed in the soft X-ray band for 40 ks with the ROSAT
High Resolution Imager (Preibisch 1997). Only 16 young stellar objects were detected
with this soft X-ray telescope, most with absorptions of 0< AV<9mag and intrinsic
luminosities of LX>1029 ergs s1. A similar exposure with Chandra with an order-
of-magnitude higher sensitivity and spatial resolution detected 127 X-ray sources. Fig-
ure 11 shows the adaptively smoothed image of the 17×17Chandra field (Getman
et al. 2002). More than 100 faint X-ray sources are easily discerned.
Figure 12 shows theoptical Hα+[S II] image of the region from Bally & Reipurth
(2001) indicating HH outflows with superposed X-ray sources. Two X-ray sources,
HJ 110 and BD +30547, are probably foreground stars (diamonds in Figure 12),
30 hard unidentified X-ray sources uniformly distributed across the field are possible
extragalactic contaminants (circles in Figure 12), and the remaining 90 X-ray sources
are cluster members (triangles and stars). Among the cluster members, eight are very
young objects (stars in Figure 12): seven are relatively lightly absorbed Class I-II stars
NGC 1333
Figure 11. An adaptively smoothed 17×17Chandra ACIS-I image of the
NGC 1333 cluster in the full 0.58.0keV band. Smoothing has been performed at
the 2.5 σlevel, and gray scales are logarithmic. More than 100 X-ray point sources
are seen. North is up and east is left.
driving jets that may have been dynamically ejected from the cloud, and one is a deeply
embedded Class I object in the vicinity of HH 7-11. It has no optical/NIR detections
but has counterparts in the radio-to-submillimeter bands.
The majority (80) of the detected cluster members are T-Tauri stars shown as
triangles in Figure 12. A few of the sub-stellar objects in the cluster may be detected
(Wilking et al. 2004). The C handra T-Tauri population is complete down to K
12 mag or 0.20.3M, assuming the known LXmass correlation and an age
of 1Myr. At the bright end, the K-band luminosity function of the X-ray cluster
agrees well with that obtained from the statistical subtraction of NIR source counts from
nearby control fields (Lada et al. 1996). With reduced sensitivity for weaker sources
Walawender et al.
Figure 12. X-ray sources are superposed on an 19.5×17.3optical Hα+[SII]
image indicating Herbig-Haro outflows and their driving sources (Bally & Reipurth
2001). Here the Chandra sources are marked as: outflow/protostellar sources (stars),
T-Tauri stars (triangles), possible extragalactic contaminants (circles), and fore-
ground sources (diamonds). XMM-Newton objects are marked by squares. The
Chandra 17×17ACIS-I field is outlined by the large square.
and lower spatial resolution, the X M M Newton observation of the region missed
20 weak Chandra cluster members and did not spatially resolve 9 Chandra visual
binaries. But there are seven sources only seen with XM M Newton: the T-Tauri star
LkHα356 in the shared field-of-view, and six additional sources outside the Chandra
field (two of these may be extragalactic contaminants). The XM M N ewton sources
are marked by boxes in Figure 12.
No matches of Chandra and XMM-Newton X-ray sources are found to any known,
deeply embedded Class 0 or sub-millimeter protostars in NGC 1333. Only two reliable
detections of the youngest protostellar objects have been reported up to date (seereview
in Getman et al. 2007): the Class 0/I protostar SMM 1B inthe R Corona Australis cloud,
and a true Class 0/I protostar BIMA 2 in the IC 1396N cometary globule. The lack of
X-ray detections from most of the known Class 0 objects does not necessarily indicate
NGC 1333
that they are X-ray quiet. X-ray observations obtained to date may not be sufficiently
sensitive to detect X-rays from these highly absorbed sources.
A handful of HH objects outside of NGC 1333 have been recently detected in
soft X-rays, tracing plasma with temperatures of a few 106to 107K produced by high
velocity HH shocks (Raga et al. 2002). X-rays from bow shocks at the jet terminus
are seen in HH 2, HH 80/81, and HH 210 (Grosso et al. 2006, and references therein)
while soft spectral components close to the protostar are seen in L1551-IRS5, DG Tau
and the Beehive in the Orion Nebula. However, none of the numerous HH objects and
outflows in NGC 1333 have been identified with theChandra and XMM-Newton X-ray
sources. This failure can be explained by the relatively low shock velocities; in HH 7-
11, for example, the jet velocities are slow (40 50 km s1) and correspondingly
the shock has low-excitation in contrast to the considerably higher shock velocities
(150 200 km s1) and higher excitation in the X-ray emitting shocks of HH 2 and
HH 210. The model by Raga et al. (2002) predicts X-ray luminosity from HH 7-11
of <1027 ergs s1, which is clearly below the sensitivity limits of the Chandra and
XMM-Newton observations.
According to Bally et al. (1996) and Bally & Reipurth (2001), a number of rel-
atively lightly absorbed young stellar objects driving jets and outflows have been dy-
namically ejected from the cloud core of the NGC 1333. Seven of these sources have
been detected in X-ray band: LkHα351, HJ 109, HJ 8, HJ 12, LkHα270, IRAS f,
and LkHα271 (stars in Figure 12). No significant differences are found between X-ray
photometry, spectral and variability characteristics of the seven jet driving sources and
the rest of the young stellar population in NGC 1333. This suggests that the presence
or absence of outflows does not produce significant differences in X-ray emission of
young stellar objects which arises mainly from violent magnetic reconnection events
near the stellar surface (Feigelson et al. 2007).
Figure 13. No difference in the X-ray luminosity functions for bright cluster
members of NGC 1333 (solid line) and IC 348 (dashed line) is found.
Walawender et al.
Figure 13 compares the absorption-corrected X-ray luminosity functions of the
77 brightest members of NGC 1333 (Getman et al. 2002) and 168 members of IC 348
(Preibisch & Zinnecker 2002). Both X-ray samples have been observed with the similar
limiting sensitivity of LX1028 ergs s1. A two-sample Kolmogorov-Smirnov test
shows no difference in the X-ray luminosity functions. This is consistent with the recent
findings in the COUP population, that the X-ray luminosity functions are relatively
insensitive to age until stars reach the main sequence (Preibisch et al. 2005).
The optically-invisible infrared source SVS 16 is perhaps the most unusual X-ray
source in NGC 1333. Infrared data show that SVS 16 is a highly obscured (AV
26 mag) binary consisting of two M-type PMS stars with a separation of 1′′ (Preibisch
et al. 1998). Mid-infrared photometry shows that both components are very young
transitional “flat spectrum” (Class I/II) objects (Rebull et al. 2003). Both Chandra
and XMM-Newton data, separated in time by more than 18 months, show X-ray flares
from SVS 16, as commonly seen in PMS systems. But, remarkably, both Chandra
and XMM-Newton spectra indicate a relatively low hydrogen column density of NH
1.22×1022 cm2. This corresponds to a visual extinction of only AV710 mag,
considerably below the AV26 mag determined from the IR spectrum and photom-
etry. Both IR and X-ray data appear reliable. This inconsistency suggests that the
plasma emitting the X-rays does not originate in the same region as the IR emission
from this source. Scenarios include X-ray emission from jet shocks close to the stel-
lar object, X-rays scattered towards the observer by circumstellar material, and huge
coronal structures.
Acknowledgments. The authors would like to thank Luisa Rebull, Colin Aspin,
and Andrew Walsh for their helpful editorial suggestions. JW was supported by the
NSF through grants AST-0507784 and AST-0407005.
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... Overall there is a high probability that the molecular cloud surrounding the parental core from which the Solar System formed was a stellar cluster that in addition gave rise to other stellar systems (Dukes and Krumholz, 2012), e.g., similar to the reflection nebula NGC 1333 in the Pereus molecular cloud (Walawender et al., 2008) or the M67 open cluster (Önehag et al., 2011). Studies of the collapse of molecular clouds and the evolution of a sub-cluster within have indicated that the inflowing gas associated with proto-stellar disks which form in a cluster environment accretes less angular momentum compared to stars which form in an isolated mode (Hayfield et al., 2011). ...
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Understanding the concept of habitability is clearly related to an evolutionary knowledge of the particular planet-in-question. However, additional indications so-called ``systemic aspects'' of the planetary system as a whole governs a particular planet's claim on habitability. In this paper we focus on such systemic aspects and discuss their relevance to the formation of an ``Earth-like'' habitable planet. This contribution summarizes our results obtained by lunar sample work and numerical models within the framework of the Research Alliance ``Planetary Evolution and Life''. We consider various scenarios which simulate the dynamical evolution of the Solar System and discuss the consequences for the likelihood of forming an Earth-like world orbiting another star. Our model approach is constrained by observations of the modern Solar System and the knowledge of its history. Results suggest that on the one hand the long-term presence of terrestrial planets is jeopardized due to gravitational interactions if giant planets are present. On the other hand the habitability of inner rocky planets may be supported in those planetary systems hosting giant planets. Gravitational interactions within a complex multiple-body structure including giant planets may supply terrestrial planets with materials which formed in the colder region of the proto-planetary disk. During these processes, water, the prime requisite for habitability, is delivered to the inner system. This may occur either during the main accretion phase of terrestrial planets or via impacts during a post-accretion bombardment. Results for both processes are summarized and discussed with reference to the lunar crater record. Starting from a scenario involving migration of the giant planets this contribution discusses the delivery of water to Earth, the modification of atmospheres by impacts in a planetary system context and the likelihood of the existence of extrasolar Earth-like habitable worlds.
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The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution Atacama Large Millimeter Array (ALMA) observations of disks and outflows now confirm several key aspects of these ideas, e.g., that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible—where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine operation.
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A set of 1.4-mm continuum measurements for a sample of 15 Galactic and extragalactic sources obtained with a millimeter-wave interferometer are presented. Maps at 3 arcsec resolution reveal compact dust emission regions in L1551 IRS 5, HH 7-11, NGC 7538 IRS 1, DR 21(OH) and Arp 220. In Arp 220 about 50 percent of the total 1.4-mm flux originates from a compact source less than 650 pc in radius centered on the NIR nucleus. The mass of interstellar matter in the central source of Arp 220 is approximately 3 X 10 to the 9th solar masses. Comparison of the 1.4 and 2.7-mm dust emission in 10 Galactic sources indicates a spectra index of 3.0 + or - 0.2 for the frequency dependence of the observed small-scale flux.
We present the results of an extensive near-infrared (JHK) imaging survey of the NGC 1333 star forming region. Our survey covers an area more than 4 times larger than the previous imaging survey of this cloud reported by Aspin et al. [A&AS, 106, 165 (1994)] and is sufficiently sensitive to render an accurate census of the embedded stellar population in the cloud. We detected 275 sources with m(K) < 14.5 magnitudes within the 432 square arcminute region surveyed. The spatial distribution of these sources is found to be significantly clustered with approximately 45% of the sources contained within two adjacent stellar clusters which together occupy an area less than 16% of the entire region surveyed. From comparison with observations of nearby control fields we estimate that roughly 143 of the sources detected over the entire region are physically associated with or embedded in the NGC 1333 molecular cloud. The majority (94 or 66%) of these are also found within the boundaries of the double cluster. From analysis of the JHK colors of the stars in the NGC 1333 region we find that roughly 30% of all sources display detectable infrared excess. This corresponds to more than 50% of all the sources embedded in the cloud. The infrared-excess sources display a higher degree of clustering than the general K band source population with roughly 75% of all excess sources located within the boundaries of the double cluster. Moreover, infrared excess sources comprise roughly 60% of the sources within the cluster suggesting that it is extremely young (less than or equal to 1-2 x 10(6) years). We also find that the stars in the cluster suffer from significant amounts of differential extinction indicating that the cluster is deeply embedded in molecular material. We construct the K luminosity function (KLF) for the NGC 1333 cloud and compare it to that of the control fields off the cloud. We find that background field stars dominate the KLF at faint magnitudes and that the vast majority of stars associated with the cloud are brighter than our completeness limit. We use the infrared colors to de-redden the stars in the cluster and construct their (de-reddened) K luminosity function. The resulting KLF of the NGC 1333 cluster is compared to the KLFs of the Trapezium cluster in Orion and IC 348, a rich young cluster located within the same GMC complex as NGC 1333. The KLFs of NGC 1333 and the Trapezium cluster are found to be very similar in shape and extent while the KLFs of NGC 1333 and IC 348 are found to differ. We attribute this to the effects of luminosity evolution in these young clusters and suggest that the NGC 1333 cluster is similar in age to the Trapezium cluster (i.e., less than or equal to 10(6) years) and significantly younger than IC 348 (i.e., <5-7X10(6) years). This is consistent with both the large population of excess sources and outflow sources [Hodapp & Ladd (ApJ, 1995) (in Press)] contained in the NGC 1333 cluster. However, we derive a star formation rate of 4 x 10(-5) M. yr(-1) for NGC 1333 which is essentially the same as that characterizing IC 348 and nearly an order of magnitude lower than that found for the Trapezium cluster. The two most active star forming regions in the Perseus cloud complex have now been throughly surveyed with comparable sensitivities at near-infrared wavelengths. Both regions have produced embedded stellar clusters, which are forming stars at a similar rate, but which appear to be in very different stages of evolution. (C) 1996 American Astronomical Society.
We present high-angular resolution molecular hydrogen (H-2) v = 1-0 S(1) line images of several well-known molecular outflow sources (DR 21, NGC 2071, HH 7-11, and HH 12). These images were obtained through a 1% narrow-band filter using an InSb infrared detector array with a plate scale of 1.2 arcsec per pixel. It is found that all of the outflow sources possess highly collimated jets of shock-excited gas that are extremely clumpy and often consist of bright knots that are placed periodically along the jet axis. The H-2, emission-line jets are significantly more collimated than their corresponding CO outflows and remain collimated to large distances from their driving source. In DR 21 and NGC 2071, the H, jets appear to become more collimated with increasing distance from the central source, suggesting that they are pressure-confined by the ambient cloud medium. In HH 7-11 and HH 12 the shock-excited ionized and molecular components are spatially coincident and appear to be of comparable shape and size; this suggests that the shocked gas is highly mixed on scales significantly smaller than the current spatial resolution (similar to 0.005 pc at 500 pc). We discuss the shock patterns observed internal to these jets and propose that they are formed by either (i) a varying external pressure, (ii) the growth of shear instabilities along the walls of a pressure-confined jet, or (iii) the collision of a highly collimated wind with numerous preexisting, subsolar mass clumps in the ambient cloud medium.
A strong water emission line has been observed at 22 GHz in the direction of NGC 1333. The maser is near an infrared source associated with a group of Herbig-Haro objects. A search of 16 other H-H objects for H2O maser emission yielded negative results.
The presence of high-velocity molecular gas associated with a low-luminosity IR source in the vicinity of the Herbig-Haro objects HH 7-11 is revealed by observations of the J=2-1 and J=1-0 transitions of (C-12)O and (C-13)O. Peak intensities spatially separated by 1.5 arcmin are shown by the blueshifted and redshifted wings, suggesting an energetic bipolar outflow of gas from a young, low-mass star. These observations imply a mass loss rate of eight million solar masses per year.
Ongoing star formation in the NGC 1333 molecular cloud is found to be the result of a cloud-cloud collision. Two velocity components at 6.3 and 8.3 km s/sup -1/ are observable in the CO and /sup 13/ CO spectra, with strong self-abosorption occurring only in the 8.3 km s/sup -1/ component. The cloud-cloud collision provides compression and heating of the back side of the 8.3 km s/sup -1/ cloud, while cool, unshocked gas on the front side of this cloud results in the observed self-absorption. With the 6.3 km s/sup -1/ cloud on the far side of the collision interface, no self-absorption occurs at this velocity. One result of the collision is the coalescence of the two velocity components into a single, intermediate velocity component observed at 7.5 km s/sup -1/. Associated with this postcollision gas is a chain of newly formed stars which illuminates and heats the nebulosity of NGC 1333.At one end of this chain of stars is a region of enhanced CO line broadening, indicating a nonhomologous gravitational collapse of this portion of the cloud. The infrared stars closest to the part of the cloud which is collapsing are completely obscured at visual wavelengths, and several are associated with Herbig-Haro (HH) objects. With increasing displacement from the region of collapse, the stars become more visible, are probably older, and the CO self-absorption decreases at these positions in the cloud.The observed region in which the cloud-cloud collision is occurring is located at the intersection of an expanding neutral hydrogen shell and lower-velocity background H I. (AIP)
IRAS 4 is a cold, low luminosity source in the active star formation region NGC 1333. The present sub-mm photometry and high spatial resolution 800- and 450-micron maps resolve this source into a binary system whose components are separated by about 31 arcsec and connected by a bridge of faint dust emission. The dust masses associated with the binary component are by far the largest seen toward any star of comparable luminosity, and are a factor of 10 higher than predicted by protostar models. It is suggested that these observations indicate a very young stellar system, possibly an actual protostar, in which most luminosity is generated by accretion.
A survey of high-velocity molecular gas toward 49 Herbig-Haro objects is presented. Observations of the (C-12)O J = 1-0 transition obtained with the 14 m telescope of the Five College Radio Astronomy Observatory reveal three new spatially extended high-velocity molecular outflows. One is in the NGC 1333 region near HH 12, and two are in the NGC 7129 region, the first near LkH-alpha 234 and the second near a far-infrared source. The relationship between optical Herbig-Haro emission knots and large-scale motions of the ambient molecular material is investigated, and the properties of high-velocity molecular outflows in the vicinity of Herbig-Haro objects are discussed. Of 11 energetic outflows in the vicinity of Herbig-Haro objects, eight are found in four pairs separated by 0.2-1.0 pc. It is estimated that energetic outflows characterized by mass loss rates equal to or greater than 10 to the -7th solar masses per yr occur for at least 10,000 yr once in the lifetime of all stars with masses greater than 1 solar mass.