J/ApJS/257/57 Cold molecular gas in merger remnants. II. (Ueda+, 2021)
Cold molecular gas in merger remnants.
II. The properties of dense molecular gas.
Ueda J., Iono D., Yun M.S., Michiyama T., Watanabe Y., Snell R.L.,
Rosa-Gonzalez D., Saito T., Vega O., Yamashita T.
<Astrophys. J. Suppl. Ser., 257, 57 (2021)>
=2021ApJS..257...57U 2021ApJS..257...57U
ADC_Keywords: Galaxies, spectra; Millimetric/submm sources; Molecular data
Keywords: Galaxy mergers ; Extragalactic astronomy ; Galaxy evolution ;
Galaxy interactions ; Star formation ; Millimeter astronomy ;
Interstellar line emission
Abstract:
We present the 3mm wavelength spectra of 28 local galaxy merger
remnants obtained with the Large Millimeter Telescope. Sixteen
molecular lines from 14 different molecular species and isotopologues
were identified, and 21 out of 28 sources were detected in one or more
molecular lines. On average, the line ratios of the dense gas tracers,
such as HCN(1-0) and HCO+(1-0), to 13CO(1-0) are 3-4 times higher
in ultra/luminous infrared galaxies (U/LIRGs) than in non-LIRGs in our
sample. These high line ratios could be explained by the deficiency of
13CO and high dense gas fractions suggested by high
HCN(1-0)/12CO(1-0) ratios. We calculate the IR-to-HCN(1-0)
luminosity ratio as a proxy of the dense gas star formation
efficiency. There is no correlation between the IR/HCN ratio and the
IR luminosity, while the IR/HCN ratio varies from source to source
((1.1-6.5)x103L☉/(K.km/s.pc2)). Compared with the control
sample, we find that the average IR/HCN ratio of the merger remnants
is higher by a factor of 2-3 than those of the early/mid-stage mergers
and nonmerging LIRGs, and it is comparable to that of the late-stage
mergers. The IR-to-12CO(1-0) ratios show a similar trend to the
IR/HCN ratios. These results suggest that star formation efficiency is
enhanced by the merging process and maintained at high levels even
after the final coalescence. The dynamical interactions and mergers
could change the star formation mode and continue to impact the star
formation properties of the gas in the postmerger phase.
Description:
Multiline observations toward 28 merger remnants were carried out
using the Large Millimeter Telescope (LMT) between 2014 October and
2015 May in its early science phase (frequency range 73-111GHz with a
spectral resolution of 31.25MHz).
We also used the CO(1-0) data of six sources (Arp 187, AM 0956-282,
NGC 3597, AM 1300-233, AM 2055-425, and NGC 7252) obtained with the
Atacama Large Millimeter/submillimeter Array (ALMA) 12m array and the
Atacama Compact Array (ACA: 7m array + Total Power (TP) array) as part
of 2011.0.00099.S, 2016.2.00006.S, and 2017.1.01003.S.
In addition, we used the CO(1-0) data of NGC 3256 obtained with the
ALMA 12m (TM2) array and the ACA 7m array as part of 2016.2.00042.S,
2016.2.00094.S, and 2018.1.00223.S.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 28 Merger remnant sub-sample
table3.dat 98 194 Properties of molecular lines
table4.dat 86 21 Molecular line luminosities
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See also:
J/AJ/114/2381 : UBVI photometry of NGC 7252 (Miller+, 1997)
J/ApJS/206/1 : Mid-IR properties of GOALS nearby LIRGs (Stierwalt+, 2013)
J/A+A/579/A101 : 3mm molecular line survey of 8 AGN (Aladro+, 2015)
J/A+A/628/A71 : CO spectra of 55 LIRGs and ULIRGs (Herrero-Illana+, 2019)
J/ApJ/880/127 : EMPIRE: IRAM 30m dense gas survey (Jimenez-Donaire+, 2019)
J/A+A/633/A163 : Mrk 231 CO(1-0) and CN(1-0) line observations (Cicone+, 2020)
J/A+A/635/A4 : HCN-to-HNC intensity ratio (Hacar+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name
13- 14 I2 h RAh Hour of Right Ascension (J2000)
16- 17 I2 min RAm Minute of Right Ascension (J2000)
19- 20 I2 s RAs Second of Right Ascension (J2000)
22- 22 A1 --- DE- Sign of the Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 30 I2 arcsec DEs Arcsecond of Declination (J2000)
32- 36 F5.1 Mpc DistL [13.6/181.7] Luminosity distance
38- 40 I3 pc/arcsec Scale [65/810] Scale
42- 46 I5 km/s Vsys [980/12840] Systemic velocity,
Rothberg & Joseph (2004AJ....128.2098R 2004AJ....128.2098R)
48- 48 A1 --- l_logLFIR Limit flag on logLFIR
49- 53 F5.2 [Lsun] logLFIR [9.05/12.37] log of FIR luminosity (1)
55- 55 A1 --- l_logLIR Limit flag on logLIR
56- 60 F5.2 [Lsun] logLIR [9.13/12.52] log of IR luminosity (1)
62- 66 F5.2 arcsec RadCO [1.85/36.9] Radius of maximum CO extent (2)
68- 72 F5.2 --- Rratio [0.01/16]? Extent of molecular gas
to stellar component (2)
74- 77 F4.2 --- e_Rratio [0.01/3]? Uncertainty in Ratio
79- 83 A5 --- Class Classification ("LIRG": 11 occurrences;
"ULIRG": 2 occurrences)
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Note (1): FIR and IR luminosity estimated using the IRAS catalogs, but the
IR luminosities of Arp187, AM1158-333, UGC9829, UGC10675, and NGC7135
are estimated using LIR=1.2*LFIR. This is based on the average
LIR/LFIR (1.2±0.1) of our sample except for two AGN-host galaxies.
Note (2): The radius enclosing the maximum extent of the CO distribution , and
the extent of molecular gas relative to the stellar component are from
Ueda+ (2014ApJS..214....1U 2014ApJS..214....1U).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name
13- 16 F4.2 mK rms [0.14/0.4] RMS noise level of spectrum
18- 42 A25 --- Line Molecular Line
44- 48 I5 km/s Vlsr [1020/12343]? Central LSR velocity of
the molecular line
50- 51 I2 km/s e_Vlsr [1/69]? Uncertainty in Vlsr
53- 53 A1 --- l_TApeak limit flag for TApeak
55- 59 F5.2 mK TApeak [0.45/36.35] Peak antenna temperature
61- 64 F4.2 mK e_TApeak [0.14/0.38]? Uncertainty in TApeak
66- 66 A1 --- f_TApeak a = tentative detection of line
68- 69 I2 --- Nch [2/17] Number, channels with >1.5σ (RMS)
71- 74 I4 km/s dV [166/1382] Linewidth,
Nch * velocity channel width
76- 76 A1 --- l_I Limit flag on I
78- 81 F4.2 K.km/s I [0.08/9.7] Integrated line intensity
or upper limit
83- 86 F4.2 K.km/s e_I [0.02/0.11]? Uncertainty on I (1)
88- 88 A1 --- l_SdV Limit flag on SdV
90- 94 F5.2 Jy.km/s SdV [0.58/67.2] Integrated flux density
or upper limit (2)
96- 98 F3.1 Jy.km/s e_SdV [0.2/0.8]? Uncertainty in SdV (2)
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Note (1): Errors estimated from
e_I = rms * linewidth per channel * square root of the number of channels,
or rms*dVch*sqrt(Nch).
Note (2): Unit of the integrated flux density, SdV, is converted from antenna
temperature to Jansky using a Kelvin-to-Jansky conversion factor of
7Jy.K(TA*)-1.
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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- 11 A11 --- Name Source name
13- 13 A1 --- l_LHCN Limit flag on LHCN
15- 21 E7.1 K.km/s.pc2 LHCN [1000000/1500000000] Line luminosity, HCN
23- 29 E7.1 K.km/s.pc2 e_LHCN [3e+06/3e+08]? Uncertainty in LHCN
31- 31 A1 --- l_LHCO+ Limit flag on LHCO+
33- 39 E7.1 K.km/s.pc2 LHCO+ [1000000/1400000000] Line luminosity, HCO+
41- 47 E7.1 K.km/s.pc2 e_LHCO+ [5e+06/3e+08]? Uncertainty in LHCO+
49- 49 A1 --- l_LHNC Limit flag on LHNC
51- 57 E7.1 K.km/s.pc2 LHNC [950000/500000000] Line luminosity, HNC
59- 65 E7.1 K.km/s.pc2 e_LHNC [1e+07/1.1e+08]? Uncertainty in LHNC
67- 67 A1 --- l_LCO Limit flag on LCO
69- 75 E7.1 K.km/s.pc2 LCO [1.1e+07/6.6e+09]? Line luminosity, LCO
77- 83 E7.1 K.km/s.pc2 e_LCO [0/800000000]? Uncertainty in LCO
85- 86 I2 --- Ref ? Reference for LCO (1)
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Note (1): References as follows:
1 = This work
2 = Herrero-Illana et al. (2019, J/A+A/628/A71)
3 = Bertram et al. (2006A&A...448...29B 2006A&A...448...29B)
4 = Costagliola et al. (2011A&A...528A..30C 2011A&A...528A..30C)
5 = Garcia-Burillo et al. (2012A&A...539A...8G 2012A&A...539A...8G)
6 = Jutte et al. (2010A&A...509A..19J 2010A&A...509A..19J)
7 = Aladro et al. (2015, J/A+A/579/A101)
8 = Solomon et al. (1997ApJ...478..144S 1997ApJ...478..144S)
9 = Garland et al. (2005ApJ...624..714G 2005ApJ...624..714G)
10 = Zhu et al. (1999AJ....118..145Z 1999AJ....118..145Z)
11 = Sanders et al. (1991ApJ...370..158S 1991ApJ...370..158S)
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History:
From electronic version of the journal
References:
Ueda et al. Paper I. 2014ApJS..214....1U 2014ApJS..214....1U
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Mar-2022