D. C. Kim

GOALS: The Great Observatories All-Sky LIRG Survey

ABSTRACT.The Great Observatories All-Sky LIRG Survey (GOALS20) combines data from NASA’s Spitzer Space Telescope, Chandra X-Ray Observatory, Hubble Space Telescope (HST), and Galaxy Evolution Explorer (GALEX) observatories, together with ground-based data, into a comprehensive imaging and spectroscopic survey of over 200 low-redshift (zxa0<xa00.088z<0.088), Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of the IRAS Revised Bright Galaxy Sample (RBGS), which comprises 629 extragalactic objects with 60xa0μm flux densities above 5.24xa0Jy, and Galactic latitudes above five degrees. The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams (type-1 and type-2 AGN, LINERs, and starbursts) as well as interaction stages (major mergers, minor mergers, and isolated galaxies). 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 powe...

MID-INFRARED SPECTRAL DIAGNOSTICS OF LUMINOUS INFRARED GALAXIES

We present a statistical analysis of 248 luminous infrared galaxies (LIRGs) which comprise the Great Observatories All-sky LIRG Survey (GOALS) observed with the Infrared Spectrograph (IRS) on-board Spitzer in the rest-frame wavelength range between 5 and 38 µm. The GOALS sample enables a direct measurement of the relative contributions of star-formation and active galactic nuclei (AGN) to the total infrared (IR) emission from a large, statistically complete sample of LIRGs in the local Universe.Several diagnostics effective at isolating the AGN contribution to the Mid-infrared (MIR) emission using [NeV], [OIV] and [NeII] gas emission lines, the 6.2 µm PAH equivalent width (EQW) and the shape of the MIR continuum are compared. The [NeV] line which indicates the presence of an AGN is detected in 22% of all LIRGs. The 6.2 µm PAH EQW, [NeV]/L_(IR), [NeV]/[NeII] and [OIV]/[NeII] ratios, and the ratios of 6.2 µm PAH flux to the integrated continuum flux between 5.3 and 5.8 µm suggest values of around 10% for the fractional AGN contribution to the total IR luminosity of LIRGs. The median of these estimates suggests that for local LIRGs the fractional AGN contribution to the total IR luminosity is ~12%. AGN dominated LIRGs have higher global and nuclear IR luminosities, warmer MIR colors and are interacting more than starburst (SB) dominated LIRGs. However there are no obvious linear correlations between these properties, suggesting that none of these properties alone can determine the activity and evolution of an individual LIRG. A study of the IRAC colors of LIRGs confirms that methods of finding AGN on the basis of their MIR colors are effective at choosing AGN but 50% to 40% of AGN dominated LIRGs are not selected as such with these methods.

THE NUCLEAR STRUCTURE IN NEARBY LUMINOUS INFRARED GALAXIES: HUBBLE SPACE TELESCOPE NICMOS IMAGING OF THE GOALS SAMPLE

We present results of Hubble Space Telescope NICMOS H-band imaging of 73 of most luminous (i.e., log[L_IR/L_0]>11.4) Infrared Galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey (GOALS). This dataset combines multi-wavelength imaging and spectroscopic data from space (Spitzer, HST, GALEX, and Chandra) and ground-based telescopes. In this paper we use the high-resolution near-infrared data to recover nuclear structure that is obscured by dust at optical wavelengths and measure the evolution in this structure along the merger sequence. A large fraction of all galaxies in our sample possess double nuclei (~63%) or show evidence for triple nuclei (~6%). Half of these double nuclei are not visible in the HST B-band images due to dust obscuration. The majority of interacting LIRGs have remaining merger timescales of 0.3 to 1.3 Gyrs, based on the projected nuclear separations and the mass ratio of nuclei. We find that the bulge luminosity surface density increases significantly along the merger sequence (primarily due to a decrease of the bulge radius), while the bulge luminosity shows a small increase towards late merger stages. No significant increase of the bulge Sersic index is found. LIRGs that show no interaction features have on average a significantly larger bulge luminosity, suggesting that non merging LIRGs have larger bulge masses than merging LIRGs. This may be related to the flux limited nature of the sample and the fact that mergers can significantly boost the IR luminosity of otherwise low luminosity galaxies. We find that the projected nuclear separation is significantly smaller for ULIRGs (median value of 1.2 kpc) than for LIRGs (mean value of 6.7 kpc), suggesting that the LIRG phase appears earlier in mergers than the ULIRG phase.

MID-INFRARED PROPERTIES OF LUMINOUS INFRARED GALAXIES. II. PROBING THE DUST AND GAS PHYSICS OF THE GOALS SAMPLE

The Great Observatories All-sky LIRG Survey (GOALS) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here, we present the results of a multi-component, spectral decomposition analysis of the low-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph spectra from 5–38 u2009μm of 244 LIRG nuclei. The detailed fits and high-quality spectra allow for characterization of the individual polycyclic aromatic hydrocarbon (PAH) features, warm molecular hydrogen emission, and optical depths for both silicate dust grains and water ices. We find that starbursting LIRGs, which make up the majority of the GOALS sample, are very consistent in their MIR properties (i.e., τ_(9.7u2009μm), τ_(ice), neon line ratios, and PAH feature ratios). However, as their EQW6.2u2009μm decreases, usually an indicator of an increasingly dominant active galactic nucleus (AGN), LIRGs cover a larger spread in these MIR parameters. The contribution from PAH emission to the total IR luminosity (L(PAH)/L(IR)) in LIRGs varies from 2%–29% and LIRGs prior to their first encounter show significantly higher L(PAH)/L(IR) ratios on average. We observe a correlation between the strength of the starburst (represented by IR8 = L_(IR)/L_(8u2009μm)) and the PAH fraction at 8u2009μm but no obvious link between IR8 and the 7.7 to 11.3 PAH ratio, suggesting that the fractional photodissociation region (PDR) emission, and not the overall grain properties, is associated with the rise in IR8 for galaxies off the starburst main sequence. We detect crystalline silicate features in ~6% of the sample but only in the most obscure sources (s_(9.7u2009μm) < −1.24). Ice absorption features are observed in ~11% (56%) of GOALS LIRGs (ULIRGs) in sources with a range of silicate depths. Most GOALS LIRGs have L(H2)/L(PAH) ratios elevated above those observed for normal star-forming galaxies and exhibit a trend for increasing L(H2)/L(PAH) ratio with increasing L(H2). While star formation appears to be the dominant process responsible for exciting the H2 in most of the GOALS galaxies, a subset of LIRGs (~10%) shows excess H2 emission that is inconsistent with PDR models and may be excited by shocks or AGN-induced outflows.

THE BURIED STARBURST IN THE INTERACTING GALAXY II Zw 096 AS REVEALED BY THE SPITZER SPACE TELESCOPE

An analysis of data from the Spitzer Space Telescope, Hubble Space Telescope, Chandra X-ray Observatory, and AKARI Infrared Astronomy Satellite is presented for the z = 0.036 merging galaxy system II Zw 096 (CGCG 448-020). Because II Zw 096 has an infrared luminosity of log(L_(IR)/L_☉) = 11.94, it is classified as a Luminous Infrared Galaxy (LIRG), and was observed as part of the Great Observatories All-sky LIRG Survey (GOALS). The Spitzer data suggest that 80% of the total infrared luminosity comes from an extremely compact, red source not associated with the nuclei of the merging galaxies. The Spitzer mid-infrared spectra indicate no high-ionization lines from a buried active galactic nucleus in this source. The strong detection of the 3.3 μm and 6.2 μm polycyclic aromatic hydrocarbon emission features in the AKARI and Spitzer spectra also implies that the energy source of II Zw 096 is a starburst. Based on Spitzer infrared imaging and AKARI near-infrared spectroscopy, the star formation rate is estimated to be 120 M_☉ yr^(-1) and >45 M_☉ yr^(-1), respectively. Finally, the high-resolution B-, I-, and H-band images show many star clusters in the interacting system. The colors of these clusters suggest at least two populations—one with an age of 1-5 Myr and one with an age of 20-500 Myr, reddened by 0-2 mag of visual extinction. The masses of these clusters span a range between 10^6 and 10^8 M_☉. This starburst source is reminiscent of the extranuclear starburst seen in NGC 4038/9 (the Antennae Galaxies) and Arp 299 but approximately an order of magnitude more luminous than the Antennae. The source is remarkable in that the off-nuclear infrared luminosity dominates the entire system.

EXCITATION MECHANISMS FOR HCN(1–0) AND HCO+(1–0) IN GALAXIES FROM THE GREAT OBSERVATORIES ALL-SKY LIRG SURVEY*

We present new IRAM 30m spectroscopic observations of the

The build-up of nuclear stellar cusps in extreme starburst galaxies and major mergers

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The Great Observatories All-Sky LIRG Survey: Herschel Image Atlas and Aperture Photometry

GHz band, including emission from the CCH (n=1-0) multiplet, HCN (1-0), HCO+ (1-0), and HNC (1-0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM data with literature data and Spitzer/IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGN) and star formation to the mid-infrared luminosity of each system. We find the HCN (1-0) emission to be enhanced in AGN-dominated systems (

A Potential Recoiling Supermassive Black Hole, CXO J101527.2+625911

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KINEMATICALLY IDENTIFIED RECOILING SUPERMASSIVE BLACK HOLE CANDIDATES IN SDSS QSOs WITH z < 0.25

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