J/ApJ/790/124 Dust and gas physics of the GOALS sample (Stierwalt+, 2014)
Mid-infrared properties of luminous infrared galaxies. II. Probing the dust and gas physics of the GOALS sample. Stierwalt S., Armus L., Charmandaris V., Diaz-Santos T., Marshall J., Evans A.S., Haan S., Howell J., Iwasawa K., Kim D.C., Murphy E.J., Rich J.A., Spoon H.W.W., Inami H., Petric A.O., U V. <Astrophys. J., 790, 124 (2014)> =2014ApJ...790..124S (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxies, IR ; Equivalent widths ; Spectra, infrared Keywords: galaxies: interactions - galaxies: nuclei - galaxies: starburst - galaxies: star formation Abstract: 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 µm 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_9.7 µm_, τice, neon line ratios, and PAH feature ratios). However, as their EQW_6.2 µm_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 = LIR/L_8 µm_) and the PAH fraction at 8 µm 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_9.7 µm_< -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 H2emission that is inconsistent with PDR models and may be excited by shocks or AGN-induced outflows. Description: Of the 180 luminous (1011 < LIR/L☉< 1012) and 22 ultraluminous (LIR > 1012 L_☉) IR systems comprising the GOALS sample, several are multiple interacting galaxies that are resolved in the MIR. As a result, 244 individual galaxy nuclei were targeted for MIR spectroscopy using the low-resolution short-low (SL: 5.5-14.5 um) and long-low (LL: 14-35 um) modules of the Spitzer IRS (Houck et al. 2004ApJS..154...18H). New staring mode observations were obtained for 157 of the LIRG systems (PID 30323; PI: L. Armus), and archival low-resolution staring or mapping mode data were acquired for the remainder of the sample. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 137 244 Fitted Mid-IR Spectral Parameters for the GOALS Sample table2.dat 139 244 H2 Line Fluxes for the GOALS Sample
See also: J/MNRAS/395/1695 : Spitzer mid-IR spectroscopy of LIRGs (Hernan-Caballero+, 2009) J/ApJ/715/572 : GOALS UV and FIR properties (Howell+, 2010) J/ApJ/741/32 : Spatial extent of (U)LIRGs in the MIR. II. (Diaz-Santos+, 2011) J/AJ/144/148 : Infrared photometry of brown dwarf and Hyper-LIRG (Griffith+, 2012) J/ApJS/206/1 : Mid-IR properties of GOALS nearby LIRGs (Stierwalt+, 2013) J/A+A/590/A67 : Ionized gas maps of local U/LIRGs (Piqueras-Lopez+, 2016) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 17 A17 --- Name Source name 18- 21 A4 --- f_Name [*,** ] Flag on Name (G1) 23 A1 --- l_EQW6.2 Limit flag on EQW6.2 24- 28 F5.2 um EQW6.2 ? 6.2 micron PAH equivalent width (2) 30- 33 F4.2 um e_EQW6.2 ? Uncertainty in EQW6.2 35 A1 --- f_EQW6.2 [i] Flag on EQW6.2 (2) 37 A1 --- l_6.2PAH Limit flag on 6.2PAH 38- 43 F6.3 10-15W/m2 6.2PAH ? 6.2 micron PAH feature flux (3) 45- 49 F5.3 10-15W/m2 e_6.2PAH ? Uncertainty in 6.2PAH (3) 51- 57 F7.3 10-15W/m2 7.7PAH ? 7.7 micron complex PAH feature flux (3) 59- 64 F6.3 10-15W/m2 e_7.7PAH ? Uncertainty in 7.7PAH (3) 66- 71 F6.3 10-15W/m2 11.3PAH ? 11.3 micron complex PAH feature flux (3) 73- 77 F5.3 10-15W/m2 e_11.3PAH ? Uncertainty in 11.3PAH (3) 79 A1 --- l_17PAH Limit flag on 17PAH 80- 86 F7.3 10-15W/m2 17PAH ? 17 micron complex PAH feature flux (3) 88- 92 F5.3 10-15W/m2 e_17PAH ? Uncertainty in 17PAH (3) 94 A1 --- l_LPAH Limit flag on LPAH 95-101 F7.2 10+9Lsun LPAH ? PAH luminosity (4) 103-106 F4.2 10+9Lsun e_LPAH ? Uncertainty in LPAH 108-111 F4.2 --- tauice ? 6.0 micron ice feature optical depth (4) 113-116 F4.2 --- e_tauice ? Uncertainty in tauice 118-121 F4.2 --- tau9.7 ? 9.7 micron silicate feature optical depth (4) 123-126 F4.2 --- e_tau9.7 ? Uncertainty in tau9.7 128-132 F5.2 --- eta ? Measure of total-to-slit flux ratio at 8 microns (5) 134-137 F4.2 --- e_eta ? Uncertainty in eta
Note (2): i = 6.2µm PAH equivalent width was calculated assuming an icy source. Note (3): In units of 10-12 ergs/s/cm2. An entry and uncertainty of 9.999 ± 9.999 indicates a nondetection or an inadequate fit to the spectrum, see Note (G1). A blank indicates no IRS data was available. Note (4): An entry and uncertainty of 9.99 ± 9.99 indicates an inadequate fit to the spectrum, see Note (G1). A blank indicates no IRS data was available. Note (5): eta = log(FtotIRAC[8 micron]/FslitIRS[8 micron]). A blank indicates no IRS or resolved IRAC data were available or multiple nuclei were contained within the IRS slit.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 17 A17 --- Name Source name 18- 21 A4 --- f_Name [*,** ] Flag on Name (G1) 23 A1 --- l_H2S-0 The 3σ upper limit flag on H2S-0 24- 29 F6.3 10-16W/m2 H2S-0 ? H2S-0 line feature flux (2) 31- 35 F5.3 10-16W/m2 e_H2S-0 ? Uncertainty in H2S-0 37 A1 --- l_H2S-1 The 3σ upper limit flag on H2S-1 38- 45 F8.3 10-16W/m2 H2S-1 ? H2S-1 line feature flux (2) 47- 51 F5.3 10-16W/m2 e_H2S-1 ? Uncertainty in H2S-1 53 A1 --- l_H2S-2 The 3σ upper limit flag on H2S-2 54- 59 F6.3 10-16W/m2 H2S-2 ? H2S-2 line feature flux (2) 61- 65 F5.3 10-16W/m2 e_H2S-2 ? Uncertainty in H2S-2 67 A1 --- l_H2S-3 The 3σ upper limit flag on H2S-3 68- 73 F6.3 10-16W/m2 H2S-3 ? H2S-3 line feature flux (2) 75- 79 F5.3 10-16W/m2 e_H2S-3 ? Uncertainty in H2S-3 81 A1 --- l_H2S-4 The 3σ upper limit flag on H2S-4 82- 88 F7.3 10-16W/m2 H2S-4 ? H2S-4 line feature flux (2) 90- 94 F5.3 10-16W/m2 e_H2S-4 ? Uncertainty in H2S-4 96 A1 --- l_H2S-5 The 3σ upper limit flag on H2S-5 97-103 F7.3 10-16W/m2 H2S-5 ? H2S-5 line feature flux (2) 105-109 F5.3 10-16W/m2 e_H2S-5 ? Uncertainty in H2S-5 111 A1 --- l_H2S-6 The 3σ upper limit flag on H2S-6 112-118 F7.3 10-16W/m2 H2S-6 ? H2S-6 line feature flux (2) 120-124 F5.3 10-16W/m2 e_H2S-6 ? Uncertainty in H2S-6 126 A1 --- l_H2S-7 The 3σ upper limit flag on H2S-7 127-133 F7.3 10-16W/m2 H2S-7 ? H2S-7 line feature flux (2) 135-139 F5.3 10-16W/m2 e_H2S-7 ? Uncertainty in H2S-7
Note (2): In units of 10-13 ergs/s/cm2. Blank line feature fluxes indicate that no IRS data was available.
Global notes : Note (G1): Flag as follows : * = Spectrum could not be adequately fit by spectral decomposition due to the presence of crystalline silicates, an unusually shallow spectral slope, or a lack of features in the MIR (see text). ** = Multiple nuclei fall within the larger LL slit. When spectral lines are well-fit, their parameters are given, but they likely represent contributions from both galaxies and so are marked as upper limits.
History: From electronic version of the journal References : Stierwalt et al., Paper I, 2013ApJS..206....1S
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Mar-2017
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