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S. Veilleux,
D. S. N. Rupke,
D. -C. Kim,
R. Genzel,
E. Sturm,
D. Lutz,
A. Contursi,
M. Schweitzer,
L. J. Tacconi,
H. Netzer,
A. Sternberg,
J. C. Mihos,
A J Baker,
J. M. Mozzarella,
S. Lord,
D. B. Sanders,
A. Stockton,
R. D. Joseph,
J. E. Barnes
[show abstract]
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ABSTRACT: We report the results from a comprehensive study of 74 ultraluminous infrared galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within z ~ 0.3$ observed with the Spitzer Infrared Spectrograph (IRS). The contribution of nuclear activity to the bolometric luminosity in these systems is quantified using six independent methods that span a range in wavelength and give consistent results within ~ +/-10-15% on average. The average derived AGN contribution in ULIRGs is ~35-40%, ranging from ~15-35% among "cool" (f_25/f_60 =< 0.2) optically classified HII-like and LINER ULIRGs to ~50 and ~75% among warm Seyfert 2 and Seyfert 1 ULIRGs, respectively. This number exceeds ~80% in PG QSOs. ULIRGs fall in one of three distinct AGN classes: (1) objects with small extinctions and large PAH equivalent widths are highly starburst-dominated; (2) systems with large extinctions and modest PAH equivalent widths have larger AGN contributions, but still tend to be starburst-dominated; and (3) ULIRGs with both small extinctions and small PAH equivalent widths host AGN that are at least as powerful as the starbursts. The AGN contributions in class 2 ULIRGs are more uncertain than in the other objects, and we cannot formally rule out the possibility that these objects represent a physically distinct type of ULIRGs. A morphological trend is seen along the sequence (1)-(2)-(3), in general agreement with the standard ULIRG - QSO evolution scenario and suggestive of a broad peak in extinction during the intermediate stages of merger evolution. However, the scatter in this sequence, implies that black hole accretion, in addition to depending on the merger phase, also has a strong chaotic/random component, as in local AGN. (abridged) Comment: 61 pages, 39 figures, 16 tables, accepted for publication in ApJS, June 2009 issue. Unabbreviated version can be found at http://www.astro.umd.edu/~veilleux/pubs/quest4.pdf
05/2009;
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L. Armus,
J. M. Mazzarella,
A. S. Evans,
J. A. Surace,
D. B. Sanders,
K. Iwasawa,
D. T. Frayer,
J. H. Howell,
B. Chan,
A. O. Petric, [......],
J. A. Marshall,
J. E. Melbourne,
J. Rich,
S. Satyapal,
B. Schulz,
H. W. W. Spoon,
E. Sturm,
V. U, S. Veilleux,
K Xu
[show abstract]
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ABSTRACT: The Great Observatories All-sky LIRG Survey (GOALS) combines data from NASA's Spitzer, Chandra, Hubble and GALEX observatories, together with ground-based data into a comprehensive imaging and spectroscopic survey of over 200 low redshift Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of the IRAS Revised Bright Galaxy Sample (RBGS). The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams as well as interaction stages. They provide an unbiased picture of the processes responsible for enhanced infrared emission in galaxies in the local Universe. As an example of the analytic power of the multi-wavelength GOALS dataset, we present data for the interacting system VV 340 (IRAS F14547+2449). Between 80-95% of the total far-infrared emission (or about 5E11 solar luminosities) originates in VV 340 North. While the IRAC colors of VV 340 North and South are consistent with star-forming galaxies, both the Spitzer IRS and Chandra ACIS data indicate the presence of a buried AGN in VV 340 North. The GALEX far and near-UV fluxes imply a extremely large infrared "excess" (IRX) for the system (IR/FUV = 81) which is well above the correlation seen in starburst galaxies. Most of this excess is driven by VV 340 N, which alone has an IR excess of nearly 400. The VV 340 system seems to be comprised of two very different galaxies - an infrared luminous edge-on galaxy (VV 340 North) that dominates the long-wavelength emission from the system and which hosts a buried AGN, and a face-on starburst (VV 340 South) that dominates the short-wavelength emission. Comment: 17 pages, 2 tables, 7 postscript figures. Accepted for publication in PASP. Updated manuscript includes complete source table (Table 1)
04/2009;
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E. Sturm,
M. Schweitzer,
D. Lutz,
A. Contursi,
R. Genzel,
M. D. Lehnert,
L. J. Tacconi, S. Veilleux,
D. S. Rupke,
D.-C. Kim,
A. Sternberg,
D. Maoz,
S. Lord,
J. Mazzarella,
and D. B. Sanders
[show abstract]
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ABSTRACT: We report the first detection of ~10 and ~18 μm silicate dust emissions in a low-luminosity active galactic nucleus (AGN), obtained in Spitzer IRS 7-37 μm spectroscopy of the type 1 LINER galaxy NGC 3998. Silicate emissions in AGNs have only recently been detected in several quasars. Our detection counters suggestions that silicate emissions are present only in the most luminous AGNs. The silicate features may be signatures of a dusty "obscuring torus" viewed face-on as postulated for type 1 AGNs. However, the apparently cool (~200 K) dust is inconsistent with theoretical expectations of much hotter torus walls. Furthermore, not all type 1 objects are silicate emission sources. Alternatively, the silicate emission may originate in dust not directly associated with a torus. We find that the long-wavelength (20 μm) tail of the emission in NGC 3998 is significantly weaker than in the sample of bright QSOs recently presented by Hao et al. The 10 μm profile in our NGC 3998 spectrum is inconsistent with "standard" silicate ISM dust. This may indicate differences in the dust composition, grain size distribution, or degree of crystallization. The differences between NGC 3998, QSOs, and Galactic templates suggest that there are significant environmental variations.
The Astrophysical Journal 12/2008; 629(1):L21. · 6.02 Impact Factor
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E. Sturm,
D. Rupke,
A. Contursi,
D.-C. Kim,
D. Lutz,
H. Netzer, S. Veilleux,
R. Genzel,
M. Lehnert,
L. J. Tacconi,
D. Maoz,
J. Mazzarella,
S. Lord,
D. Sanders,
and A. Sternberg
[show abstract]
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ABSTRACT: We report results from the first mid-infrared spectroscopic study of a comprehensive sample of 33 LINERs, observed with the Spitzer Space Telescope. We compare the properties of two different LINER populations: infrared-faint LINERs, with LINER emission arising mostly in compact nuclear regions, and infrared-luminous LINERs, which often show spatially extended (non-AGN) LINER emission. We show that these two populations can be easily distinguished by their mid-infrared spectra in three different ways: (1) their mid-IR spectral energy distributions (SEDs), (2) the emission features of polycyclic aromatic hydrocarbons (PAHs), and (3) various combinations of IR fine-structure line ratios. IR-luminous LINERs show mid-IR SEDs typical of starburst galaxies, while the mid-IR SEDs of IR-faint LINERs are much bluer. PAH flux ratios are significantly different in the two groups. Fine-structure emission lines from highly excited gas, such as [O IV], are detected in both populations, suggesting the presence of an additional AGN in a large fraction of IR-bright LINERs as well, which contributes little to the combined mid-IR light. The two LINER groups occupy different regions of mid-infrared emission-line excitation diagrams. The positions of the various LINER types in our diagnostic diagrams provide important clues regarding the power source of each LINER type. Most of these mid-infrared diagnostics can be applied at low spectral resolution, making AGN- and starburst-excited LINERs distinguishable at high redshifts as well.
The Astrophysical Journal 12/2008; 653(1):L13. · 6.02 Impact Factor
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M. Schweitzer,
D. Lutz,
E. Sturm,
A. Contursi,
L. J. Tacconi,
M. D. Lehnert,
K. M. Dasyra,
R. Genzel, S. Veilleux,
D. Rupke,
D.-C. Kim,
A. J. Baker,
H. Netzer,
A. Sternberg,
J. Mazzarella,
and S. Lord
[show abstract]
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ABSTRACT: This paper addresses the origin of the far-infrared (FIR) continuum of QSOs, based on the Quasar and ULIRG Evolution Study (QUEST) of nearby QSOs and ULIRGs using observations with the Spitzer Space Telescope. For 27 Palomar-Green QSOs at z 0.3, we derive luminosities of diagnostic lines ([Ne II] 12.8 μm, [Ne V] 14.3 μm, [O IV] 25.9 μm) and emission features (PAH 7.7 μm emission, which is related to star formation), as well as continuum luminosities over a range of mid- to far-infrared wavelengths between 6 and 60 μm. We detect star-formation-related PAH emission in 11/26 QSOs and fine-structure line emission in all of them, often in multiple lines. The detection of PAHs in the average spectrum of sources that lack individual PAH detections provides further evidence for the widespread presence of PAHs in QSOs. Similar PAH/FIR and [Ne II]/FIR ratios are found in QSOs and in starburst-dominated ULIRGs and lower luminosity starbursts. We conclude that the typical QSO in our sample has at least 30% but likely most of the far-infrared luminosity (~1010-1012 L) arising from star formation, with a tendency for larger star formation contribution at the largest FIR luminosities. In the QSO sample, we find correlations between most of the quantities studied including combinations of AGN tracers and starburst tracers. The common scaling of AGN and starburst luminosities (and fluxes) is evidence for a starburst-AGN connection in luminous AGN. Strong correlations of far-infrared continuum and starburst related quantities (PAH, low-excitation [Ne II]) offer additional support for the starburst origin of far-infrared emission.
The Astrophysical Journal 12/2008; 649(1):79. · 6.02 Impact Factor
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M. Schweitzer,
B. Groves,
H. Netzer,
D. Lutz,
E. Sturm,
A. Contursi,
R. Genzel,
L. J. Tacconi, S. Veilleux,
D.-C. Kim,
D. Rupke,
and A. J. Baker
[show abstract]
[hide abstract]
ABSTRACT: This paper addresses the origin of the silicate emission observed in PG QSOs, based on observations with the Spitzer Space Telescope. Scenarios based on the unified model suggest that silicate emission in AGNs arises mainly from the illuminated faces of the clouds in the torus at temperatures near sublimation. However, detections of silicate emission in type 2 QSOs, and the estimated cool dust temperatures, argue for a more extended emission region. To investigate this issue we present the mid-infrared spectra of 23 QSOs. These spectra, and especially the silicate emission features at ~10 and ~18 μm, can be fitted using dusty narrow-line region (NLR) models and a combination of blackbodies. The bolometric luminosities of the QSOs allow us to derive the radial distances and covering factors for the silicate-emitting dust. The inferred radii are 100-200 times larger than the dust sublimation radius, much larger than the expected dimensions of the inner torus. Our QSO mid-IR spectra are consistent with the bulk of the silicate dust emission arising from the dust in the innermost parts of the NLR.
The Astrophysical Journal 12/2008; 679(1):101. · 6.02 Impact Factor
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ABSTRACT: We present host galaxy velocity dispersions of 12 local (mainly Palomar-Green) QSOs measured directly from the stellar CO absorption features in the H band. The mean bulge dispersion of the QSOs in our sample is 186 km s-1 with a standard deviation of 24 km s-1. The measurement of the stellar dispersion in QSOs enables us to place them on observational diagrams such as the local black hole mass-bulge velocity dispersion relation and the fundamental plane of early-type galaxies. Concerning the former relation, these QSOs have higher black hole masses than most Seyfert 1 AGNs with similar velocity dispersions. On the fundamental plane, PG QSOs are located between the regions occupied by moderate-mass and giant ellipticals. The QSO bulge and black hole masses, computed from the stellar velocity dispersions, are of order 1011 and 108 M, respectively. The Eddington efficiency of their black holes is on average 0.25, assuming that all of the bolometric luminosity originates from the active nucleus. Our data are consistent with other lines of evidence that Palomar-Green QSOs are related to galaxy mergers with gas-rich components and that they are formed in a manner similar to the most massive ultraluminous infrared galaxies, regardless of their far-infrared emission. However, PG QSOs seem to have smaller host dispersions and different formation mechanisms than QSOs with supermassive black holes of 5 × 108-109 M that accrete at low rates and reside in massive spheroids.
The Astrophysical Journal 12/2008; 657(1):102. · 6.02 Impact Factor
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[show abstract]
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ABSTRACT: We present Spitzer rest-frame mid-infrared spectroscopy of twelve z~2 mm-bright type 1 QSOs, selected from unlensed and lensed QSO samples and covering a range of AGN optical luminosities L_5100=10^45 to 10^47 erg/s. On top of the AGN continuum, we detect PAH emission from luminous star formation in nine objects individually as well as in the composite spectrum for the full sample. PAH luminosity and rest frame far-infrared luminosity correlate and extend the similar correlation for lower luminosity local QSOs. This provides strong evidence for intense star formation in the hosts of these mm-bright QSOs, sometimes exceeding 1000 Msun/yr and dominating their rest frame far-infrared emission. The PAH-based limit on star formation rates is lower for luminous z~2 QSOs that are not preselected for their mm emission. Partly dependent on systematic changes of the AGN dust covering factor and the dust spectral energy distribution of the AGN proper, the spectral energy distributions of mm-faint high-z QSOs may be AGN dominated out to rest frame far-infrared wavelengths. Towards the most luminous high-z QSOs, there is a flattening of the relation between star formation and AGN luminosity that is observed for lower redshift QSOs. No QSO in our sample has a PAH-measured star formation rate in excess of 3000 Msun/yr. Comment: Accepted for publication in ApJ, 25 pages, 7 eps figures
05/2008;
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M. Schweitzer,
B. Groves,
H. Netzer,
D. Lutz,
E. Sturm,
A. Contursi,
R. Genzel,
L. J. Tacconi, S. Veilleux,
D. -C. Kim,
D. Rupke,
A J Baker
[show abstract]
[hide abstract]
ABSTRACT: This paper addresses the origin of the silicate emission observed in PG QSOs, based on observations with the Spitzer Space Telescope. Scenarios based on the unified model suggest that silicate emission in AGN arises mainly from the illuminated faces of the clouds in the torus at temperatures near sublimation. However, detections of silicate emission in Type 2 QSOs, and the estimated cool dust temperatures, argue for a more extended emission region.To investigate this issue we present the mid-infrared spectra of 23 QSOs. These spectra, and especially the silicate emission features at ~10 and ~18 mu can be fitted using dusty narrow line region (NLR) models and a combination of black bodies. The bolometric luminosities of the QSOs allow us to derive the radial distances and covering factors for the silicate-emitting dust. The inferred radii are 100-200 times larger than the dust sublimation radius, much larger than the expected dimensions of the inner torus. Our QSO mid-IR spectra are consistent with the bulk of the silicate dust emission arising from the dust in the innermost parts of the NLR. Comment: 39 pages, 8 figures
01/2008;
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[hide abstract]
ABSTRACT: We report on the detection of Fe Kalpha emission in F04103$-$2838, an ultraluminous infrared galaxy (ULIRG; log[L$_{\rm IR}$/L$_\odot$] $\ge$ 12) that is optically classified as a LINER. Previous {\it Chandra} observations suggested the presence of both a starburst and an AGN in this source. A deeper ($\sim$20 ksec) {\it XMM-Newton} spectrum reveals an Fe Kalpha line at rest frame energy $\sim$6.4 keV, consistent with cold neutral iron. The best-fit spectral model indicates the Fe Kalpha line has an equivalent width of $\sim$1.6 keV. The hard X-ray emission is dominated by a Compton-thick AGN with intrinsic 0.2--10 keV luminosity $\sim10^{44}$ ergs s$^{-1}$, while the soft X-ray emission is from $\sim$0.1 keV gas attributed to the starburst. The X-ray spectrum of this source bears a striking resemblance to that of the archetypal luminous infrared galaxy NGC 6240 despite differences in merger state and infrared properties. Comment: 23 pre-print pages including 5 figures and 1 table. Accepted by ApJ
10/2007;
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[show abstract]
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ABSTRACT: Galactic winds are important in recycling energy and metals in galaxies. They are also suspected to be the primary mechanism
in the enrichment of the intergalactic medium. New observations are revealing the ubiquity of galactic winds, particularly
at high redshift. We review the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift
universe.
Astrophysics and Space Science 09/2007; 311(1):87-98. · 1.69 Impact Factor
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ABSTRACT: We report the first detection of the 6.2micron and 7.7micron infrared `PAH' emission features in the spectrum of a high redshift QSO, from the Spitzer-IRS spectrum of the Cloverleaf lensed QSO (H1413+117, z~2.56). The ratio of PAH features and rest frame far-infrared emission is the same as in lower luminosity star forming ultraluminous infrared galaxies and in local PG QSOs, supporting a predominantly starburst nature of the Cloverleaf's huge far-infrared luminosity (5.4E12 Lsun, corrected for lensing). The Cloverleaf's period of dominant QSO activity (Lbol ~ 7E13 Lsun) is coincident with an intense (star formation rate ~1000 Msun/yr) and short (gas exhaustion time ~3E7yr) star forming event. Comment: Accepted for publication as an ApJ Letter. 14 pages, 3 figures.
04/2007;
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K. M. Dasyra,
L. J. Tacconi,
R. I. Davies,
T. Naab,
R. Genzel,
D. Lutz,
E. Sturm,
A J Baker, S. Veilleux,
D. B. Sanders,
A. Burkert
[show abstract]
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ABSTRACT: We present results from our Very Large Telescope large program to study the dynamical evolution of local Ultraluminous Infrared Galaxies (ULIRGs) and QSOs. This paper is the second in a series presenting the stellar kinematics of 54 ULIRGs, derived from high resolution, long-slit H- and K-band spectroscopy. The data presented here, including observations of 17 new targets, are mainly focused on sources that have coalesced into a single nucleus. The stellar kinematics, extracted from the CO ro-vibrational bandheads in our spectra, indicate that ULIRG remnants are dynamically heated systems with a mean dispersion of 161 km/s. The combination of kinematic, structural, and photometric properties of the remnants indicate that they mostly originate from major mergers and that they result in the formation of systems supported by random motions, therefore, elliptical galaxies. The peak of the velocity dispersion distribution and the locus of ULIRGs on the fundamental plane of early-type galaxies indicate that the end products of ultraluminous mergers are typically moderate-mass ellipticals (of stellar mass ~10^10 - 10^11 M_sun). Converting the host dispersion into black hole mass with the aid of the M_BH-sigma relation yields black hole mass estimates of the order 10^7 - 10^8 M_sun and high accretion rates with Eddington efficiencies often >0.5.
08/2006;
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ABSTRACT: We present an emission-line diagnostic analysis of integral-field
spectroscopic observations that cover the central kiloparsec of NGC 7742. This
Sa galaxy hosts a spectacular nuclear starburst ring and nuclear regions
characterized by low-ionization emission. The gas in the ring rotates in the
opposite sense to the stars in the galaxy, suggesting a recent merging or
acquisition event. The combination of integral-field measurements for the
H-alpha + [NII] emission lines from DensePak and the H-beta and [OIII] emission
from Sauron allow the construction of diagnostic diagrams that highlight the
transition from star formation in the nuclear ring to excitation by
high-velocity shocks or by a central AGN towards the center. DensePak
measurements for the [SII] line ratio reveal very low gas densities in the
nuclear ring, Ne < 100 per cm^3, characteristic of massive HII regions.
Comparison with MAPPINGS III models for starbursts with low gas densities show
that the ring is of roughly solar metallicity. This suggests that the gas in
the nuclear ring originated in a stellar system capable of substantially
enriching the gas metallicity through sustained star formation. We suggest that
NGC 7742 cannibalised a smaller galaxy rich in metal-poor gas, and that star
formation episodes in the ring have since increased the metallicity to its
present value.
07/2006;
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L Yan,
F Bertoldi,
A Blain,
K Caputi,
C Cesarsky,
H Dole,
B Draine,
D Fadda,
H Flores,
D Frayer,
R Genzel,
G Helou,
G Lagache,
E Le Floc'h,
D Lutz,
J -L Puget,
A Sajina,
D Sanders,
H Spoon, S Veilleux
Spitzer Proposal. 05/2006;
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[show abstract]
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ABSTRACT: We report the results from a deep HST NICMOS H-band imaging survey of a carefully selected sample of 33 luminous, late-stage galactic mergers at z < 0.3. Signs of a recent galactic interaction are seen in all of the objects in the HST sample, including all 7 IR-excess Palomar-Green (PG) QSOs in the sample. Unsuspected double nuclei are detected in 5 ULIRGs. A detailed two-dimensional analysis of the surface brightness distributions in these objects indicates that the great majority (81%) of the single-nucleus systems show a prominent early-type morphology. However, low-surface-brightness exponential disks are detected on large scale in at least 4 of these sources. The hosts of 'warm' AGN-like systems are of early type and have less pronounced merger-induced morphological anomalies than the hosts of cool systems with LINER or HII region-like nuclear optical spectral types. The host sizes and luminosities of the 7 PG~QSOs in our sample are statistically indistinguishable from those of the ULIRG hosts. In comparison, highly luminous quasars, such as those studied by Dunlop et al. (2003), have hosts which are larger and more luminous. The hosts of ULIRGs and PG QSOs lie close to the locations of intermediate-size (about 1 -- 2 L*) spheroids in the photometric projection of the fundamental plane of ellipticals, although there is a tendency in our sample for the ULIRGs with small hosts to be brighter than normal spheroids. Excess emission from a young stellar population in the ULIRG/QSO hosts may be at the origin of this difference. Our results provide support for a possible merger-driven evolutionary connection between cool ULIRGs, warm ULIRGs, and PG~QSOs although this sequence may break down at low luminosity. (abridged) Comment: Paper to be published in the Astrophysical Journal; revised based on comments from referee. A PDF file combining both text and figures is available at http://www.astro.umd.edu/~veilleux/pubs/nicmos.pdf
01/2006;
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ABSTRACT: We present a study of the dynamical evolution of Ultraluminous Infrared Galaxies (ULIRGs), merging galaxies of infrared luminosity >10^12 L_sun. During our Very Large Telescope large program, we have obtained ISAAC near-infrared, high-resolution spectra of 54 ULIRGs (at several merger phases) and 12 local Palomar-Green QSOs to investigate whether ULIRGs go through a QSO phase during their evolution. One possible evolutionary scenario is that after nuclear coalescence, the black hole radiates close to Eddington to produce QSO luminosities. The mean stellar velocity dispersion that we measure from our spectra is similar (~160 km/s) for 30 post-coalescence ULIRGs and 7 IR-bright QSOs. The black holes in both populations have masses of order 10^7-10^8 M_sun (calculated from the relation to the host dispersion) and accrete at rates >0.5 Eddington. Placing ULIRGs and IR-bright QSOs on the fundamental plane of early-type galaxies shows that they are located on a similar region (that of moderate-mass ellipticals), in contrast to giant ellipticals and radio-loud QSOs. While this preliminary comparison of the ULIRG and QSO host kinematical properties indicates that (some) ULIRGs may undergo a QSO phase in their evolutionary history before they settle down as ellipticals, further data on non-IR excess QSOs are necessary to test this scenario. Comment: To appear in the "QSO Host Galaxies: Evolution and Environment" conference proceedings; meeting held in Leiden, August 2005
12/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We present first results from our Very Large Telescope large program to study the dynamical evolution of Ultraluminous Infrared Galaxies (ULIRGs), which are the products of mergers of gas-rich galaxies. The full data set consists of high resolution, long-slit, H- and K-band spectra of 38 ULIRGs and 12 QSOs (between 0.042<z<0.268). In this paper, we present the sources that have not fully coalesced, and therefore have two distinct nuclei. This sub-sample consists of 21 ULIRGs, the nuclear separation of which varies between 1.6 and 23.3 kpc. From the CO bandheads that appear in our spectra, we extract the stellar velocity dispersion, sigma, and the rotational velocity, V_rot. The stellar dispersion equals 142 km/s on average, while V_rot is often of the same order. We combine our spectroscopic results with high-resolution infrared (IR) imaging data to study the conditions for ULIRG activity in interacting pairs. We find that the majority of ULIRGs are triggered by almost equal-mass major mergers of 1.5:1 average ratio. Less frequently, 3:1 encounters are also observed in our sample. However, less violent mergers of mass ratio >3:1 typically do not force enough gas into the center to generate ULIRG luminosities. Comment: Accepted for publication in "The Astrophysical Journal"
10/2005;
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[hide abstract]
ABSTRACT: We present results from Chandra observations of 14 ultraluminous infrared galaxies (ULIRGs; log(L_IR/L_Sun) >= 12) with redshifts between 0.04 and 0.16. The goals of the observations were to investigate any correlation between infrared color or luminosity and the properties of the X-ray emission and to attempt to determine whether these objects are powered by starbursts or active galactic nuclei (AGNs). The sample contains approximately the same number of high and low luminosity objects and ``warm'' and ``cool'' ULIRGs. All 14 galaxies were detected by Chandra. Our analysis shows that the X-ray emission of the two Seyfert 1 galaxies in our sample are dominated by AGN. The remaining 12 sources are too faint for conventional spectral fitting to be applicable. Hardness ratios were used to estimate the spectral properties of these faint sources. The photon indices for our sample plus the Chandra-observed sample from Ptak et al.(2003) peak in the range of 1.0-1.5, consistent with expectations for X-ray binaries in a starburst, an absorbed AGN, or hot bremsstrahlung from a starburst or AGN. The values of photon index for the objects in our sample classified as Seyferts (type 1 or 2) are larger than 2, while those classified as HII regions or LINERs tend to be less than 2. The hard X-ray to far-infrared ratios for the 12 weak sources are similar to those of starbursts, but we cannot rule out the possibility of absorbed, possibly Compton-thick, AGNs in some of these objects. Two of these faint sources were found to have X-ray counterparts to their double optical and infrared nuclei. Comment: 40 pages, 5 tables, 14 figures, accepted by ApJ
08/2005;
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[show abstract]
[hide abstract]
ABSTRACT: Galaxy-scale winds are poised to solve a number of ailments in modern
cosmology. However, we know little about trends of wind properties with
host galaxy properties. In an attempt to quantify the impact of
galactic winds on their host galaxies and the environment, we are
conducting a systematic survey of star-forming and active galaxies at z
= 0 - 0.5. Preliminary results are presented.
05/2005; 331:313.
