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[show abstract]
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ABSTRACT: We use Spitzer IRS spectroscopy to study the nature 65 IR-luminous galaxies
at 0.02 < z < 0.6 with F(24micron) > 1.2mJy. The IRS spectra cover wavelengths
spanning the PAH features and important atomic diagnostic lines. Our sample
corresponds to L(IR) = L(8-1000micron) = 10^10-10^12 Lsun. We divide our
galaxies into those with Spitzer IRAC colors indicative of warm dust heated by
an AGN (IRAGN) and those whose colors indicate star-formation processes
(non-IRAGN). Compared to the non-IRAGN, the IRAGN show smaller PAH emission
EWs, which we attribute to an increase in mid-IR continuum from the AGN. We
find that in both the IRAGN and non-IRAGN samples, the PAH luminosities
correlate strongly with the [Ne II] emission, from which we conclude that the
PAH luminosity directly traces the instantaneous SFR in both the IRAGN and
non-IRAGN galaxies. We compare the ratio of PAH luminosity to the total IR
luminosity and show that for most IRAGN star-formation accounts for 10-50% of
the L(IR). We also find no measurable difference between the PAH luminosity
ratios of L(11.3)/L(7.7) and L(6.2)/L(7.7) for the IRAGN and non-IRAGN,
suggesting that AGN do not significantly excite or destroy PAH molecules on
galaxy-wide scales. A small subset of galaxies show excess of [O IV] emission
compared to their PAH emission, which indicates the presence of
heavily-obscured AGN, including 3 galaxies that are not otherwise selected as
IRAGN. The low PAH emission and low [Ne II] emission of the IRAGN and [O
IV]-excess objects imply they have low SFRs and their IR luminosity is
dominated by processes associated with the AGN.
04/2013;
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[show abstract]
[hide abstract]
ABSTRACT: Local luminous infrared (IR) galaxies (LIRGs) have both high star formation
rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence.
Therefore, they are ideal candidates to explore the co-evolution of black hole
(BH) growth and star formation (SF) activity, not necessarily associated with
major mergers. Here, we use Spitzer/IRS spectroscopy of a complete
volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical
BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas
velocity dispersions and literature stellar velocity dispersions. We find that
in a large fraction of local LIRGs the current SFR is taking place not only in
the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH
luminosities, but also in the host galaxy. We next use the ratios between the
SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH
growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to
BHAR ratios higher than those of optically selected Seyferts of similar AGN
luminosities. However, the majority of the IR-bright galaxies in the RSA
Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be
higher in local LIRGs with the lowest SFRs. All this suggests that in local
LIRGs there is a distinct IR-bright star forming phase taking place prior to
the bulk of the current BH growth (i.e., AGN phase). The latter is reflected
first as a composite and then as a Seyfert, and later as a non-LIRG optically
identified Seyfert nucleus with moderate SF in its host galaxy.
01/2013;
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Hannah Broekhoven-Fiene,
Brenda C. Matthews,
Grant M. Kennedy,
Mark Booth,
Bruce Sibthorpe,
Samantha M. Lawler,
J. J. Kavelaars,
Mark C. Wyatt,
Chenruo Qi,
Alice Koning,
Kate Y. L. Su, George H. Rieke,
David J. Wilner,
Jane S. Greaves,
for the DEBRIS collaboration
[show abstract]
[hide abstract]
ABSTRACT: We present observations of the debris disk around gamma Doradus, an F1V star,
from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free
Reconnaissance in the Infrared/Submillimetre). The disk is well-resolved at 70,
100 and 160 micron, resolved along its major axis at 250 micron, detected but
not resolved at 350 micron, and confused with a background source at 500
micron. It is one of our best resolved targets and we find it to have a
radially broad dust distribution. The modelling of the resolved images cannot
distinguish between two configurations: an arrangement of a warm inner ring at
several AU (best-fit 4 AU) and a cool outer belt extending from ~55 to 400 AU
or an arrangement of two cool, narrow rings at ~70 AU and ~190 AU. This
suggests that any configuration between these two is also possible. Both models
have a total fractional luminosity of ~10^{-5} and are consistent with the disk
being aligned with the stellar equator. The inner edge of either possible
configuration suggests that the most likely region to find planets in this
system would be within ~55 AU of the star. A transient event is not needed to
explain the warm dust's fractional luminosity.
12/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We explore the collisional decay of disk mass and infrared emission in debris
disks. With models, we show that the rate of the decay varies throughout the
evolution of the disks, increasing its rate up to a certain point, which is
followed by a leveling off to a slower value. The total disk mass falls off ~
t^-0.35 at its fastest point (where t is time) for our reference model, while
the dust mass and its proxy -- the infrared excess emission -- fades
significantly faster (~ t^-0.8). These later level off to a decay rate of
M_tot(t) ~ t^-0.08 and M_dust(t) or L_ir(t) ~ t^-0.6. This is slower than the ~
t^-1 decay given for all three system parameters by traditional analytic
models.
We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100
micron observations. Assuming a log-normal distribution of initial disk masses,
we generate model population decay curves for the fraction of debris disk
harboring stars observed at 24 micron and also model the distribution of
measured excesses at the far-IR wavelengths (70-100 micron) at certain age
regimes. We show general agreement at 24 micron between the decay of our
numerical collisional population synthesis model and observations up to a Gyr.
We associate offsets above a Gyr to stochastic events in a few select systems.
We cannot fit the decay in the far infrared convincingly with grain strength
properties appropriate for silicates, but those of water ice give fits more
consistent with the observations.
11/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We develop a new numerical algorithm to model collisional cascades in debris disks. Because of the large dynamical range in particle masses, we solve the integro-differential equations describing erosive and catastrophic collisions in a particle-in-a-box approach, while treating the orbital dynamics of the particles in an approximate fashion. We employ a new scheme for describing erosive (cratering) collisions that yields a continuous set of outcomes as a function of colliding masses. We demonstrate the stability and convergence characteristics of our algorithm and compare it with other treatments. We show that incorporating the effects of erosive collisions results in a decay of the particle distribution that is significantly faster than with purely catastrophic collisions.
The Astrophysical Journal 11/2012; 749. · 6.02 Impact Factor
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Mark Booth,
Grant Kennedy,
Bruce Sibthorpe,
Brenda C. Matthews,
Mark C. Wyatt,
Gaspard Duchêne,
J. J. Kavelaars,
David Rodriguez,
Jane S. Greaves,
Alice Koning,
Laura Vican, George H. Rieke,
Kate Y. L. Su,
Amaya Moro-Martín,
Paul Kalas
[show abstract]
[hide abstract]
ABSTRACT: The majority of debris discs discovered so far have only been detected
through infrared excess emission above stellar photospheres. While disc
properties can be inferred from unresolved photometry alone under various
assumptions for the physical properties of dust grains, there is a degeneracy
between disc radius and dust temperature that depends on the grain size
distribution and optical properties. By resolving the disc we can measure the
actual location of the dust. The launch of Herschel, with an angular resolution
superior to previous far-infrared telescopes, allows us to spatially resolve
more discs and locate the dust directly. Here we present the nine resolved
discs around A stars between 20 and 40 pc observed by the DEBRIS survey. We use
these data to investigate the disc radii by fitting narrow ring models to
images at 70, 100 and 160 {\mu}m and by fitting blackbodies to full spectral
energy distributions. We do this with the aim of finding an improved way of
estimating disc radii for unresolved systems. The ratio between the resolved
and blackbody radii varies between 1 and 2.5. This ratio is inversely
correlated with luminosity and any remaining discrepancies are most likely
explained by differences to the minimum size of grain in the size distribution
or differences in composition. We find that three of the systems are well fit
by a narrow ring, two systems are borderline cases and the other four likely
require wider or multiple rings to fully explain the observations, reflecting
the diversity of planetary systems.
10/2012;
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[show abstract]
[hide abstract]
ABSTRACT: Debris disks with extremely large infrared excesses (fractional luminosities
$> 10^{-2}$) are rare. Those with ages between 30 and 130 Myr are of interest
because their evolution has progressed well beyond that of protoplanetary disks
(which dissipate with a timescale of order 3 Myr), yet they represent a period
when dynamical models suggest that terrestrial planet building may still be
progressing through large, violent collisions that could yield large amounts of
debris and large infrared excesses. For example, our Moon was formed through a
violent collision of two large proto-planets during this age range. We report
two disks around the solar-like stars ID8 and HD 23514 in this age range where
the 24 {\mu}m infrared excesses vary on timescales of a few years, even though
the stars are not variable in the optical. Variations this rapid are difficult
to understand if the debris is produced by collisional cascades, as it is for
most debris disks. It is possible that the debris in these two systems arises
in part from condensates from silicate-rich vapor produced in a series of
violent collisions among relatively large bodies. If their evolution is rapid,
the rate of detection of extreme excesses would indicate that major collisions
may be relatively common in this age range.
05/2012;
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[show abstract]
[hide abstract]
ABSTRACT: Luminous infrared galaxies (LIRGs) provide insights into star formation (SF) and nuclear activity (AGN) under extreme conditions.
We are carrying out a multi-wavelength (X-rays, ultraviolet through mid-infrared, and radio) program to obtain high angular
resolution observations of a volume-limited sample of local LIRGs. The typical distances to these LIRGs (D=35–75 Mpc) allow us to identify star clusters and H II regions on scales of tens to hundreds of parsecs. We present here
recent results on properties of the massive star-forming regions and star clusters in two LIRGs in our sample, Arp299 and
NGC7469.
KeywordsGalaxies: star clusters, H II regions-Infrared: galaxies
Astrophysics and Space Science 04/2012; 324(2):333-336. · 1.69 Impact Factor
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Jonathan P. Gardner,
John C. Mather,
Mark Clampin,
Rene Doyon,
Matthew A. Greenhouse,
Heidi B. Hammel,
John B. Hutchings,
Peter Jakobsen,
Simon J. Lilly,
Knox S. Long, [......],
John Nella, George H. Rieke,
Marcia J. Rieke,
Hans-Walter Rix,
Eric P. Smith,
George Sonneborn,
Massimo Stiavelli,
H. S. Stockman,
Rogier A. Windhorst,
Gillian S. Wright
[show abstract]
[hide abstract]
ABSTRACT: The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m.The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations.To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.
Space Science Reviews 04/2012; 123(4):485-606. · 3.61 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 μm) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L IR = 1011-1012 L ☉). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 μm spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is ~62%. The derived AGN bolometric luminosities are in the range L bol(AGN) = (0.4-50) × 1043 erg s–1. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L bol[AGN]/L IR ≤ 0.05. Only 8% of local LIRGs have a significant AGN bolometric contribution L bol[AGN]/L IR > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L IR = 1012-1013 L ☉), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of ΩAGN IR = 3 × 105 L ☉ Mpc–3 in LIRGs.
The Astrophysical Journal 12/2011; 744(1):2. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We explore the evolution of the mass distribution of dust in
collision-dominated debris disks, using the collisional code introduced in our
previous paper. We analyze the equilibrium distribution and its dependence on
model parameters by evolving over 100 models to 10 Gyr. With our numerical
models, we confirm that systems reach collisional equilibrium with a mass
distribution that is steeper than the traditional solution by Dohnanyi (1969).
Our model yields a quasi steady-state slope of n(m) ~ m^{-1.88} [n(a) ~
a^{-3.65}] as a robust solution for a wide range of possible model parameters.
We also show that a simple power-law function can be an appropriate
approximation for the mass distribution of particles in certain regimes. The
steeper solution has observable effects in the submillimeter and millimeter
wavelength regimes of the electromagnetic spectrum. We assemble data for nine
debris disks that have been observed at these wavelengths and, using a
simplified absorption efficiency model, show that the predicted slope of the
particle mass distribution generates SEDs that are in agreement with the
observed ones.
11/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We quantify the active galactic nucleus (AGN) contribution to the
mid-infrared (mid-IR) and the total infrared (IR, 8-1000micron) emission in a
complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs).
We decompose the Spitzer Infrared Spectrograph (IRS) low-resolution 5-38micron
spectra of the LIRGs into AGN and starburst components using clumpy torus
models and star-forming galaxy templates, respectively. We find that 50%
(25/50) of local LIRGs have an AGN component detected with this method. There
is good agreement between these AGN detections through mid-IR spectral
decomposition and other AGN indicators, such as the optical spectral class,
mid-IR spectral features and X-ray properties. Taking all the AGN indicators
together, the AGN detection rate in the individual nuclei of LIRGs is ~62%. The
derived AGN bolometric luminosities are in the range L_bol(AGN)=0.4 -50x10^{43}
erg/s. The AGN bolometric contribution to the IR luminosities of the galaxies
is generally small, with 70% of LIRGs having L_bol(AGN)/L_IR<0.05. Only ~8% of
local LIRGs have a significant AGN bolometric contribution L_bol(AGN)/L_IR >
0.25. From the comparison of our results with literature results of
ultraluminous infrared galaxies, we confirm that in the local universe the AGN
bolometric contribution to the IR luminosity increases with the IR luminosity
of the galaxy/system. If we add up the AGN bolometric luminosities we find that
AGNs only account for 5%^{+8%}_{-3%} of the total IR luminosity produced by
local LIRGs (with and without AGN detections). This proves that the bulk of the
IR luminosity of local LIRGs is due to star formation activity. Taking the
newly determined IR luminosity density of LIRGs in the local universe, we then
estimate an AGN IR luminosity density of Omega_IR(AGN) = 3x10^5 L_sun Mpc^{-3}$
in LIRGs.
09/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We study the X-ray emission of a representative sample of 27 local luminous
infrared galaxies (LIRGs). The median IR luminosity of our sample is log
L_IR/L_sun = 11.2, thus the low-luminosity end of the LIRG class is well
represented. We used new XMM-Newton data as well as Chandra and XMM-Newton
archive data. The soft X-ray (0.5-2 keV) emission of most of the galaxies
(>80%), including LIRGs hosting a Seyfert 2 nucleus, is dominated by
star-formation related processes. These LIRGs follow the star-formation rate
(SFR) versus soft X-ray luminosity correlation observed in local starbursts. We
find that ~15% of the non-Seyfert LIRGs (3 out of 20) have an excess hard X-ray
emission relative to that expected from star-formation that might indicate the
presence of an obscured AGN. The rest of the non-Seyfert LIRGs follow the SFR
versus hard X-ray (2-10 keV) luminosity correlation of local starbursts. The
non-detection of the 6.4 keV Fe K alpha emission line in the non-Seyfert LIRGs
allows us to put an upper limit to the bolometric luminosity of an obscured
AGN, L_bol <1043 erg s-1 . That is, in these galaxies, if they hosted a low
luminosity AGN, its contribution to total luminosity would be less than 10%.
Finally we estimate that the AGN contribution to the total luminosity for our
sample of local LIRGs is between 7% and 10%.
09/2011;
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Daniel J. Eisenstein,
David H. Weinberg,
Eric Agol,
Hiroaki Aihara,
Carlos Allende Prieto,
Scott F. Anderson,
James A. Arns,
Éric Aubourg,
Stephen Bailey,
Eduardo Balbinot, [......],
John P. Wisniewski,
W. Michael Wood-Vasey,
Brian Yanny,
Naoki Yasuda,
Christophe Yèche,
Donald G. York,
Erick Young,
Gail Zasowski,
Idit Zehavi,
and Bo Zhao
[show abstract]
[hide abstract]
ABSTRACT: Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Lyα forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = λ/Δλ 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R 30,000), high signal-to-noise ratio (S/N ≥ 100 per resolution element), H-band (1.51 μm < λ < 1.70 μm) spectra of 105 evolved, late-type stars, measuring separate abundances for ~15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 m s–1, ~24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z ≥ 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS.
The Astronomical Journal 08/2011; 142(3):72. · 4.03 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present estimates of black hole accretion rates and nuclear, extended, and
total star-formation rates for a complete sample of Seyfert galaxies. Using
data from the Spitzer Space Telescope, we measure the active galactic nucleus
(AGN) luminosity using the [O IV] 25.89 micron emission line and the
star-forming luminosity using the 11.3 micron aromatic feature and extended 24
micron continuum emission. We find that black hole growth is strongly
correlated with nuclear (r<1 kpc) star formation, but only weakly correlated
with extended (r>1 kpc) star formation in the host galaxy. In particular, the
nuclear star-formation rate (SFR) traced by the 11.3 micron aromatic feature
follows a relationship with the black hole accretion rate (BHAR) of the form
SFR\proptoBHAR^0.8, with an observed scatter of 0.5 dex. This SFR-BHAR
relationship persists when additional star formation in physically matched r=1
kpc apertures is included, taking the form SFR\proptoBHAR^0.6. However, the
relationship becomes almost indiscernible when total SFRs are considered. This
suggests a physical connection between the gas on sub-kpc and sub-pc scales in
local Seyfert galaxies that is not related to external processes in the host
galaxy. It also suggests that the observed scaling between star formation and
black hole growth for samples of AGNs will depend on whether the star formation
is dominated by a nuclear or extended component. We estimate the integrated
black hole and bulge growth that occurs in these galaxies and find that an AGN
duty cycle of 5-10% would maintain the ratio between black hole and bulge
masses seen in the local universe.
06/2011;
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Daniel J. Eisenstein,
David H. Weinberg,
Eric Agol,
Hiroaki Aihara,
Carlos Allende Prieto,
Scott F. Anderson,
James A. Arns,
Eric Aubourg,
Stephen Bailey,
Eduardo Balbinot, [......],
John P. Wisniewski,
W. Michael Wood-Vasey,
Brian Yanny,
Naoki Yasuda,
Christophe Yeche,
Donald G. York,
Erick Young,
Gail Zasowski,
Idit Zehavi,
Bo Zhao
[show abstract]
[hide abstract]
ABSTRACT: Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II),
SDSS-III is a program of four spectroscopic surveys on three scientific themes:
dark energy and cosmological parameters, the history and structure of the Milky
Way, and the population of giant planets around other stars. In keeping with
SDSS tradition, SDSS-III will provide regular public releases of all its data,
beginning with SDSS DR8 (which occurred in Jan 2011). This paper presents an
overview of the four SDSS-III surveys. BOSS will measure redshifts of 1.5
million massive galaxies and Lya forest spectra of 150,000 quasars, using the
BAO feature of large scale structure to obtain percent-level determinations of
the distance scale and Hubble expansion rate at z<0.7 and at z~2.5. SEGUE-2,
which is now completed, measured medium-resolution (R=1800) optical spectra of
118,000 stars in a variety of target categories, probing chemical evolution,
stellar kinematics and substructure, and the mass profile of the dark matter
halo from the solar neighborhood to distances of 100 kpc. APOGEE will obtain
high-resolution (R~30,000), high signal-to-noise (S/N>100 per resolution
element), H-band (1.51-1.70 micron) spectra of 10^5 evolved, late-type stars,
measuring separate abundances for ~15 elements per star and creating the first
high-precision spectroscopic survey of all Galactic stellar populations (bulge,
bar, disks, halo) with a uniform set of stellar tracers and spectral
diagnostics. MARVELS will monitor radial velocities of more than 8000 FGK stars
with the sensitivity and cadence (10-40 m/s, ~24 visits per star) needed to
detect giant planets with periods up to two years, providing an unprecedented
data set for understanding the formation and dynamical evolution of giant
planet systems. (Abridged)
01/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We are carrying out detailed study of the X-ray and infrared (IR) properties of a sample of local (d < 70 Mpc) luminous infrared galaxies (LIRGs) using XMM-Newton and Spitzer (imaging and spectroscopy). The main goal is to study the extreme processes of star formation and/or active galactic nuclei (AGN) taking place in this cosmologically important class of galaxies. In this proceedings we present the preliminary results obtained from the analysis of the XMM-Newton X-ray images and the X-ray spectral modeling. Comment: 5 pages, to appear in Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society held on September 13-17, 2010, in Madrid, Spain
11/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We combine nulling interferometry at 10 μm using the MMT and Keck Telescopes with spectroscopy, imaging, and photometry from 3 to 100 μm using Spitzer to study the debris disk around β Leo over a broad range of spatial scales, corresponding to radii of 0.1 to ~100 AU. We have also measured the close binary star o Leo with both Keck and MMT interferometers to verify our procedures with these instruments. The β Leo debris system has a complex structure: (1) relatively little material within 1 AU; (2) an inner component with a color temperature of ~600 K, fitted by a dusty ring from about 2–3 AU; and (3) a second component with a color temperature of ~120 K fitted by a broad dusty emission zone extending from about ~5 AU to ~55 AU. Unlike many other A-type stars with debris disks, β Leo lacks a dominant outer belt near 100 AU.
The Astrophysical Journal 11/2010; · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We used Spitzer/IRS spectroscopic data on 426 galaxies including quasars, Seyferts, LINER and HII galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne V]14.3 um and 24.3 um (97.1 eV) and the [O IV]25.9 um (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne III]15.56 um (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne III] excess due to star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due to star formation in active galaxies and determined that it dominates the [O IV] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the AGN dominates the [O IV] emission in most Seyfert galaxies, whereas star-formation adequately explains the observed [O IV] emission in optically classified HII galaxies. Finally we computed photoionization models to determine the physical conditions of the narrow line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log nH (cm-2) < 21. Comment: Accepted for Publication in ApJ, 19 pages, 13 figures
10/2010;
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ABSTRACT: We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z ~ 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z ~ 1 and a lensed galaxy at z ~ 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z > 1 for a given IR luminosity compared to their local counterparts. Comment: Accepted for publication in The Astrophysical Journal; 13 pages, 7 figures; Online materials available at http://inthanon.as.arizona.edu/~wiphu/Rujopakarn_2010b
10/2010;
