J/AJ/156/295 Warm molecular hydrogen in nearby LIRGs (Petric+, 2018)
Warm molecular hydrogen in nearby, Luminous Infrared Galaxies.
Petric A.O., Armus L., Flagey N., Guillard P., Howell J., Inami H.,
Charmandaris V., Evans A., Stierwalt S., Diaz-Santos T., Lu N., Spoon H.,
Mazzarella J., Appleton P., Chan B., Chu J., Hand D., Privon G., Sanders D.,
Surace J., Xu K., Zhao Y.
<Astron. J., 156, 295 (2018)>
=2018AJ....156..295P 2018AJ....156..295P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, IR ; Atomic physics ;
Spectra, infrared
Keywords: galaxies: active - galaxies: interactions - galaxies: ISM -
galaxies: starburst
Abstract:
Mid-infrared molecular hydrogen (H2) emission is a powerful cooling
agent in galaxy mergers and in radio galaxies; it is a potential key tracer
of gas evolution and energy dissipation associated with mergers, star
formation, and accretion onto supermassive black holes. We detect mid-IR
H2 line emission in at least one rotational transition in 91% of the
214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of
the Great Observatories All-sky LIRG Survey. We use H2 excitation diagrams
to estimate the range of masses and temperatures of warm molecular gas
in these galaxies. We find that LIRGs in which the IR emission originates
mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H2
mass-averaged excitation temperatures than LIRGs in which the IR emission
originates mostly from star formation. Between 10% and 15% of LIRGs have
H2 emission lines that are sufficiently broad to be resolved or partially
resolved by the high-resolution modules of Spitzer's Infrared Spectrograph
(IRS). Those sources tend to be mergers and contain AGN. This suggests
that a significant fraction of the H2 line emission is powered by AGN
activity through X-rays, cosmic rays, and turbulence. We find a
statistically significant correlation between the kinetic energy in the
H2 gas and the H2 to IR luminosity ratio. The sources with the largest
warm gas kinetic energies are mergers. We speculate that mergers increase
the production of bulk inflows leading to observable broad H2 profiles
and possibly denser gas.
Description:
The GOALS sample properties and selection are described in detail in
Armus et al. (2009PASP..121..559A 2009PASP..121..559A). For this investigation, we use the
spectra of 248 individual nuclei in 202 LIRG systems, observed in the
high-resolution Infrared Spectrograph (IRS) modules (Short-High and
Long-High; abbreviated SH and LH) and complementary low-resolution
(IRS Short-Low and Long-Low; abbreviated SL and LL) spectra for 234
sources. The widths of the SL, SH, LL, LH slits (3.6", 4.7", 10.7", 11.1")
correspond to 1.5, 2.0, 4.5, and 4.6 kpc, respectively, at a distance
of 88 Mpc - the median galaxy distance in our sample. The distances to
the GOALS galaxies are between 17.5 and 387 Mpc. We obtained the IRS
spectra in our own observing program (PI: Armus, PID 30323) for 158 LIRG
systems, with the IRS spectra for the remaining 44 LIRG systems taken
from the Spitzer archive.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 31 8 *H2 rotational transitions
table2.dat 76 231 H2 fluxes
table4.dat 34 27 General properties of galaxies where
the H2 S(1) is resolved or marginally resolved
table5.dat 73 214 Masses and temperatures of warm molecular gas
as estimated from MIR spectroscopy
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Note on table1.dat: Roussel et al. (2007, J/ApJ/669/959).
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See also:
J/A+A/434/149 : NIR spectroscopy of luminous IR galaxies (Valdes+, 2005)
J/A+A/451/57 : Luminous IR galaxies mid-infrared properties
(Marcillac+, 2006)
J/ApJ/669/959 : Warm molecular hydrogen in SINGS galaxy sample
(Roussel+, 2007)
J/MNRAS/395/1695 : Spitzer mid-IR spectroscopy of LIRGs
(Hernan-Caballero+, 2009)
J/ApJ/709/884 : Role of starburst-AGN composites in LIRG mergers
(Yuan+, 2010)
J/ApJ/723/993 : Spatial extent of (U)LIRGs in the MIR. I.
(Diaz-Santos+, 2010)
J/ApJ/741/32 : Spatial extent of (U)LIRGs in the MIR. II.
(Diaz-Santos+, 2011)
J/ApJ/777/156 : Spitzer/IRS spectra of GOALS luminous IR galaxies
(Inami+, 2013)
J/ApJS/206/1 : Mid-IR properties of GOALS nearby LIRGs (Stierwalt+, 2013)
J/ApJ/790/124 : Dust and gas physics of the GOALS sample (Stierwalt+, 2014)
J/ApJ/846/32 : Herschel FIR spectra of GOALS galaxies (Diaz-Santos+, 2017)
J/A+A/617/A130 : Luminous infrared galaxies AKARI 2.5-5um data (Inami+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Trans Short notation of H2 transition
6 I1 --- J0 [2/9] Upper J quantum number (1)
8 I1 --- J1 [0/7] Lower J quantum number (1)
10- 15 F6.3 um lambda [5.511/28.219] Transition rest wavelength
17- 20 I4 K Eu/k [510/7197] Rotational upper energy (2)
22- 28 F7.5 10-7/s A [0.00029/2] Transition probability from
Black & Dalgarno 1976ApJ...203..132B 1976ApJ...203..132B;
Roussel et al. 2007, J/ApJ/669/959
30- 31 I2 J g [5/57] Statistical weight for the transition
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Note (1): The transition from the upper to lower level results in the emission
of the observed line listed in the first column.
Note (2): From Black & Dalgarno 1976ApJ...203..132B 1976ApJ...203..132B; Huber & Hertzberg 1979,
Constants of Diatomic Molecules (New York: Van Nostrand); Roussel et al. 2007,
J/ApJ/669/959.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Galaxy identifier
19- 27 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
29- 35 F7.3 deg DEdeg Declination in decimal degrees (J2000)
37 A1 --- l_S(0) [<] Limit flag on S(0)
39- 41 I3 10-18W/m2 S(0) [1/225] H2 S(0) rotational emission line
flux
43- 45 I3 10-18W/m2 e_S(0) [1/286]? Uncertainty in S(0) flux
47 A1 --- l_S(1) [<] Limit flag on S(1) flux
49- 51 I3 10-18W/m2 S(1) [4/470] H2 S(1) rotational emission line
flux
53- 54 I2 10-18W/m2 e_S(1) [1/16]? Uncertainty in S(1) flux
56 A1 --- l_S(2) [<] Limit flag on S(2) flux
58- 60 I3 10-18W/m2 S(2) [2/332] H2 S(2) rotational emission line
flux
62- 64 I3 10-18W/m2 e_S(2) [1/104]? Uncertainty in S(2) flux
66 A1 --- l_S(3) [<] Limit flag on S(3) flux
68- 70 I3 10-18W/m2 S(3) [2/672]? H2 S(3) rotational emission line
flux
72- 73 I2 10-18W/m2 e_S(3) [1/17]? Uncertainty in S(3) flux
75- 76 A2 --- Merger Merger stage (1)
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Note (1): Stierwalt et al. (2014, J/ApJ/790/124) give H2 S(3) fluxes obtained
by simultaneously fitting the dust and gas absorption, emission and continuum
gas and dust features. To achieve this Stierwalt et al. (2014, J/ApJ/790/124)
scale the Short-Low (SL) spectra to match the Long-Low (LL) spectra. The GOALS
sources were classified in 5 stages, Petric et al. (2011ApJ...730...28P 2011ApJ...730...28P);
Stierwalt et al. (2013, J/ApJS/206/1), e.g. Fig. 10 in Petric et al.
(2011ApJ...730...28P 2011ApJ...730...28P). The merger classifications for each LIRG is given in
Stierwalt et al. (2013, J/ApJS/206/1) and a subset was re-evaluated by
Larson et al. (2016ApJ...825..128L 2016ApJ...825..128L).
Here we compress the merger stages in three categories:
nm = Non mergers: targets without obvious signs of morphological disturbances;
em = Early-mergers: galaxies are within 1 arcmin of each other but show little
or no morphological disturbance;
m = Mergers: this includes all other stages of gravitational interactions.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Galaxy identifier
18- 21 I4 km/s FWHM [583/1318] S(1) full-width at half-maximum
23- 26 I4 km/s FWHMi [281/1215] Intrinsic S(1) full-width at
half-maximum
28- 30 I3 km/s e_FWHMi [35/173] Uncertainty in FWHMi
32 I1 --- [NeV] [0/1] [Ne V] detection flag (1=detected;
0=not detected)
34 I1 --- [OIV] [0/1] [O IV] detection flag (1=detected;
0=not detected)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Galaxy identifier
19- 25 A7 --- OName Other galaxy identifier
27- 34 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
36- 43 F8.4 deg DEdeg Declination in decimal degrees (J2000)
45- 47 I3 K T1 [15/650] Temperature of first gas component
49- 53 F5.3 [Msun] logM1 [5.77/9.228] Log mass of first gas component
55- 57 I3 K T2 [11/863]? Temperature of second gas component
59- 63 F5.3 [Msun] logM2 [5.305/8.869]? Log mass of second gas component
65- 67 I3 K Tavg [46/650] Mass averaged temperature
69- 73 F5.3 [Msun] logMtot [5.77/9.253] Total warm H2 gas mass
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 26-Apr-2019