[show abstract][hide abstract] ABSTRACT: The Massive Young star-forming Complex Study in Infrared and X-rays (MYStIX)
project requires samples of young stars that are likely members of 20 nearby
Galactic massive star-forming regions. Membership is inferred from statistical
classification of X-ray sources, from detection of a robust infrared excess
that is best explained by circumstellar dust in a disk or infalling envelope,
and from published spectral types that are unlikely to be found among field
stars. We present the MYStIX membership lists here, and describe in detail the
statistical classification of X-ray sources via a \Naive Bayes Classi
The Astrophysical Journal Supplement Series 09/2013; 209(2). · 16.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Massive Young star-forming complex Study in Infrared and X-ray (MYStIX)
uses data from the Chandra X-ray Observatory to identify and characterize the
young stellar populations in twenty Galactic (d < 4 kpc) massive star-forming
regions. Here, the X-ray analysis for Chandra ACIS-I observations of ten of the
MYStIX ?elds is described, and a catalog of >10,000 X-ray sources is presented.
In comparison to other published Chandra source lists for the same regions, the
number of MYStIX detected faint X-ray sources in a region is often doubled.
While the higher catalog sensitivity increases the chance of false detections,
it also increases the number of matches to infrared stars. X-ray emitting
contaminants include foreground stars, background stars, and extragalactic
sources. The X-ray properties of sources in these classes are discussed.
The Astrophysical Journal Supplement Series 09/2013; 209(2). · 16.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: MYStIX (Massive Young Star-Forming Complex Study in Infrared and Xray) seeks
to characterize 20 OB-dominated young clusters and their environs at distances
d < 4 kpc using imaging detectors on the Chandra X-ray Observatory, Spitzer
Space Telescope, and the United Kingdom InfraRed Telescope. The observational
goals are to construct catalogs of star-forming complex stellar members with
well-defined criteria, and maps of nebular gas (particularly of hot X-ray
emitting plasma) and dust. A catalog of MYStIX Probable Complex Members (MPCMs)
with several hundred OB stars and > 30, 000 low mass premain sequence is
assembled. This sample and related data products will be used to seek new
empirical constraints on theoretical models of cluster formation and dynamics,
mass segregation, OB star formation, star formation triggering on the periphery
of HII regions, the survivability of protoplanetary disks in HII regions. This
paper give an introduction and overview of the project, covering the data
analysis methodology and application to two star forming regions, NGC 2264 and
the Trifid Nebula.
[show abstract][hide abstract] ABSTRACT: The MYStIX project (Massive Young Star-Forming Complex Study in Infrared and
X-rays) provides a comparative study of 20 Galactic massive star-forming
complexes (d = 0.4 to 3.6 kpc). Probable stellar members in each target complex
are identified using X-ray and/or infrared data via two pathways: (1) X-ray
detections of young/massive stars with coronal activity/strong winds; or (2)
infrared excess (IRE) selection of young stellar objects (YSOs) with
circumstellar disks and/or protostellar envelopes. We present the methodology
for the second pathway, using Spitzer/IRAC, 2MASS, and UKIRT imaging and
photometry. Although IRE selection of YSOs is welltrodden territory, MYStIX
presents unique challenges. We combine IR spectral energy distribution (SED)
fitting with IR color cuts and spatial clustering analysis to identify IRE
sources and isolate probable YSO members in each MYStIX target field from the
myriad types of contaminating sources that can resemble YSOs: extragalactic
sources, evolved stars, nebular knots, and even unassociated
foreground/background YSOs. Applying our methodology consistently across 18 of
the target complexes, we produce the MYStIX IRE Source (MIRES) Catalog
comprising 20,719 sources, including 8686 probable stellar members of the
MYStIX target complexes. We also classify the SEDs of 9365 IR counterparts to
MYStIX X-ray sources to assist the first pathway, the identification of X-ray
detected stellar members. The MIRES catalog provides a foundation for follow-up
studies of diverse phenomena related to massive star cluster formation,
including protostellar outflows, circumstellar disks, and sequential star
formation triggered by massive star feedback processes.
[show abstract][hide abstract] ABSTRACT: The MYStIX project (Massive Young stellar clusters Study in Infrared and
X-rays) is compiling comprehensive catalogs of the stellar membership in
~20 Galactic massive star-forming regions (d = 0.4 to 3.6 kpc). MYStIX
is the first project of its kind to study such a large sample of
Galactic regions in parallel, employing a homogeneous set of
multiwavelength data analysis techniques. Probable stellar members in
each target region are identified using X-ray and/or infrared photometry
via two pathways: (1) X-ray detections of young/massive stars with
coronal activity/strong winds or (2) Infrared (IR) excess selection of
young stellar objects (YSOs) with circumstellar disks and/or
protostellar envelopes. In this contribution, we present the methodology
and initial results of pathway (2), using Spitzer/IRAC, 2MASS, and
UKIDSS imaging and photometry. Although IR excess selection of YSOs is
well-trodden territory, MYStIX presents unique challenges. The target
regions run the gamut from relatively nearby, lower-mass clusters in
uncrowded fields located toward the outer Galaxy (e.g. NGC 2264, the
Flame Nebula), to massive clusters located at greater distances along
complicated, inner Galaxy sightlines (e.g. NGC 6357, M17). We have
developed a new procedure combining IR spectral energy distribution
fitting with IR color cuts and spatial clustering analysis to separate
probable YSO members in each MYStIX target field from the myriad types
of contaminating objects that resemble YSOs: extragalactic sources,
evolved stars, PAH nebular knots, and even unassociated
foreground/background YSOs. Applying this technique consistently across
our target regions, we have produced a catalog comprising several
thousand YSOs that can serve as the basis for follow-up studies of
diverse phenomena related to massive cluster formation, including
protostellar outflows, circumstellar disks, and triggered star
[show abstract][hide abstract] ABSTRACT: XPHOT is an IDL implementation of a non-parametric method for estimating
the apparent and intrinsic broad-band fluxes and absorbing X-ray column
densities of weak X-ray sources. XPHOT is intended for faint sources
with greater than ˜5-7 counts but fewer than 100-300 counts where
parametric spectral fitting methods will be superior. This method is
similar to the long-standing use of color-magnitude diagrams in optical
and infrared astronomy, with X-ray median energy replacing color index
and X-ray source counts replacing magnitude. Though XPHOT was calibrated
for thermal spectra characteristic of stars in young stellar clusters,
recalibration should be possible for some other classes of faint X-ray
sources such as extragalactic active galactic nuclei.
[show abstract][hide abstract] ABSTRACT: Observations of the spatial distributions of young stars in star-forming
regions can be linked to the theory of clustered star formation using spatial
statistical methods. The MYStIX project provides rich samples of young stars
from the nearest high-mass star-forming regions. Maps of stellar surface
density reveal diverse structure and subclustering. Young stellar clusters and
subclusters are fit with isothermal spheres and ellipsoids using the Bayesian
Information Criterion to estimate the number of subclusters. Clustering is also
investigated using Cartwright and Whitworth's Q statistic and the inhomogeneous
two-point correlation function. Mass segregation is detected in several cases,
in both centrally concentrated and fractally structured star clusters, but a
few clusters are not mass segregated.
[show abstract][hide abstract] ABSTRACT: As a result of feedback from massive stars, via their intense winds
and/or supernova explosions, massive star-forming regions are entirely
filled with hot, X-ray emitting plasmas, which escape into the ambient
ISM. As shown recently by Townsley et al. for several ``extreme" cases
(Carina, M17, NGC 3576, NGC 3603, 30 Dor), by way of large Chandra
ACIS mosaics, extra, non-thermal emission lines are present on top of
the standard lines emitted by hot plasmas. Some of them are very close
to lines characteristic of charge-exchange reactions between the hot
plasma and the cold surrounding material, suggesting that this mechanism
operates on large spatial scales (several 10 pc) in star-forming regions
in general. The connection with starburst galaxies is briefly mentioned,
and it is pointed out that supernovae interacting with molecular clouds
may also provide a good environment to look for charge exchange
[show abstract][hide abstract] ABSTRACT: ACIS Extract (AE), written in the IDL language, provides innovative and
automated solutions to the varied challenges found in the analysis of
X-ray data taken by the ACIS instrument on NASA's Chandra observatory.
AE addresses complications found in many Chandra projects: large numbers
of point sources (hundreds to several thousand), faint point sources,
misaligned multiple observations of an astronomical field, point source
crowding, and scientifically relevant diffuse emission. AE can perform
virtually all the data processing and analysis tasks that lie between
Level 2 ACIS data and publishable LaTeX tables of point-like and diffuse
source properties and spectral models.
[show abstract][hide abstract] ABSTRACT: We present first results from a 100-ks Chandra X-ray observation of the
M17 SWex giant molecular cloud. M17 SWex is an infrared dark cloud
(IRDC) resembling a flying dragon in Spitzer Space Telescope images.
This IRDC is a very young but very active region of star formation,
containing 200 intermediate-mass (2-8 Msun) young stellar objects
(YSOs) plus a few massive YSOs and ultracompact H II regions. Our
Chandra/ACIS image detected >850 X-ray point sources, spatially
clustered along the IRDC filaments and many associated with embedded,
intermediate-mass YSOs. This abundance of X-ray sources far exceeded
expectations, given the extreme youth and high extinction (AV
> 30 mag) of the region. Our preliminary results suggest that (1) M17
SWex is an even more active star-forming region than supposed, and/or
(2) young, intermediate-mass, pre-main-sequence stars have surprisingly
high X-ray luminosities. We have also found indications of diffuse, soft
X-ray emission associated with the IRDC. The origins of this diffuse
emission are mysterious.
M.S.P. is supported by an NSF Astronomy and Astrophysics Postdoctoral
Fellowship under award AST-0901646.
[show abstract][hide abstract] ABSTRACT: The Chandra Carina Complex Project (CCCP) is a 1.42deg2^ survey, at an assumed distance of 2.3kpc, of the Great Nebula in Carina with the Imaging array of the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-ray Observatory, and is described in Townsley et al. (2011ApJS..194....1T). The Very Large Project (VLP) data were acquired over nine months, from 2008 February 12 through 2008 October 15 and were completed with Chandra archive ObsID 6402 (Trumpler 16, in 2006 Aug 30), ObsID 4495 (Trumpler 14, in 2004 Sep 21), and ObsID 6578 (Treasure Chest Cluster, in 2006 Apr 16). (3 data files).
[show abstract][hide abstract] ABSTRACT: We present recent results and updates from our multi-wavelength imaging and spectroscopic studies of young stars in the W3 star-forming complex and the surrounding area including IC 1795, W3 North, W3(OH), W3 Main, W3 South, and AFGL 333. We introduce newly-found embedded clusters and aggregates in W3 South and AFGL 333. The W3/W4/W5 complexes are well-known sites of massive star formation and are ideal sites to study the triggered mode of star formation. We conducted a systematic imaging and spectroscopic survey to study the initial mass function and the evolution of circumstellar disks in such an environment. We obtained optical imaging data and spectra with the 90 Prime on the Bok telescope and the Hectospec on the MMT, respectively, and we also made use of archival infrared data from 2MASS and Spitzer and X-ray data from Chandra. We present spectroscopically confirmed young stars and discuss their stellar properties. Using improved determinations of stellar ages and masses, we analyse the circumstellar disk frequency and the disk properties of young stars for M > 0.8 Msun.
[show abstract][hide abstract] ABSTRACT: The CCCP observations and their analysis are described in detail by
Townsley et al. (2011ApJS..194....1T) and Broos et al. (2011, Cat.
J/ApJS/194/2). Twenty-two overlapping pointings with the Chandra
Advanced CCD Imaging Spectrometer (ACIS), each subtending 17'x17', were
observed. They cover a 1.4deg2^ region. The X-ray data are aligned to
the Two Micron All Sky Survey (2MASS)/Hipparcos frame and, in most
cases, source positions have accuracies better than 0.5". Infrared
counterparts are found by positional coincidences with 2MASS, VLT HAWK-I
(Preibisch et al. 2011, Cat. J/ApJS/194/10), and other published
(3 data files).
[show abstract][hide abstract] ABSTRACT: This table contains 64 optical, infrared, and x-ray photometric and spectral parameters for the 200 O- and early-B stars with determined spectral types in the Chandra Carina Complex Project (Townsley+, 2011ApJS..194....1G). Some X-ray parameters are from Global X-ray properties of the O and B stars in Carina (Naze et al., 2011, Cat. J/ApJS/194/7). Other optical/infrared parameters are from Candidate X-ray-emitting OB stars in the Carina nebula identified via infrared spectral energy distributions (Povich+, 2011ApJS..194....6G). For a complete description of column label see A catalog of Chandra X-ray sources in the Carina nebula (Broos+, 2011, Cat. J/ApJS/194/2) and Carina OB stars: X-ray signatures of wind shocks and magnetic fields (This paper). (2 data files).
[show abstract][hide abstract] ABSTRACT: File ob78_2.dat contains 64 X-ray spectral parameters used for the 78 O- and early-B stars with determined spectral types and more than 50 net counts in the Chandra Carina Complex Project (Townsley+, 2011ApJS..194....1G). Lbol values are from Povich et al. (2011, Cat. J/ApJS/194/6). Spectral types from Gagne et al. (2001, Cat. J/ApJS/194/5). See also Broos et al, (2001, Cat. J/ApJS/194/2) (8 data files).
[show abstract][hide abstract] ABSTRACT: Trumpler 15 was observed as part of the CCCP (Townsley et al., 2011ApJS..194....1T), a large mosaic of Chandra Advanced CCD Imaging Spectrometer I-array (ACIS-I) observations. One CCCP pointing (ObsID 9484, a 60ks integration obtained on 2008 August 19) is centered on Trumpler 15; five other pointings cover the edges of the cluster (Figure 1(a)). (1 data file).
[show abstract][hide abstract] ABSTRACT: The CCCP catalog (Broos et al., 2011, Cat. J/ApJS/194/2) contains over 14000 point sources detected by the Advanced CCD Imaging Spectrometer (ACIS) of the Chandra X-ray Observatory. Broos et al. matched the Vela-Carina Archive to the CCCP X-ray catalog and found 6543 counterparts to CCCP sources. The Vela-Carina Catalog is a subset of the Archive and provides mid-IR counterparts for 4664 CCCP sources. The Carina Nebula was observed with Spitzer/MIPS during 2007 July as part of program GO-30848 (MIPSCAR; PI: N. Smith). The Vela-Carina survey (Spitzer Proposal ID 40791, PI: S. R. Majewski) was modeled after the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE; Benjamin et al. 2003PASP..115..953B). (3 data files).
[show abstract][hide abstract] ABSTRACT: We present a 1.42deg2^ mosaic of diffuse X-ray emission in the Great Nebula in Carina from the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer camera. After removing >14000 X-ray point sources from the field, we smooth the remaining unresolved emission, tessellate it into segments of similar apparent surface brightness, and perform X-ray spectral fitting on those tessellates to infer the intrinsic properties of the X-ray-emitting plasma. By modeling faint resolved point sources, we estimate the contribution to the extended X-ray emission from unresolved point sources and show that the vast majority of Carina's unresolved X-ray emission is truly diffuse. Line-like correlated residuals in the X-ray spectral fits suggest that substantial X-ray emission is generated by charge exchange at the interfaces between Carina's hot, rarefied plasma and its many cold neutral pillars, ridges, and clumps. (2 data files).
[show abstract][hide abstract] ABSTRACT: HAWK-I is the new near-infrared imager at the ESO 8m Very Large Telescope, available since the year 2008. The data discussed in this paper are derived from images taken through the standard broadband J, H, and Ks filters. (1 data file).