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 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 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:
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FileName Lrecl Records Explanations
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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
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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
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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
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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.
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Byte-by-byte Description of file: table2.dat
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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.
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History:
From electronic version of the journal
References :
Stierwalt et al., Paper I, 2013ApJS..206....1S 2013ApJS..206....1S
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Mar-2017