J/ApJ/927/149 Low-J CO line ratios for 152 CO map pairs (Leroy+, 2022)
Low-J CO line ratios from single-dish CO mapping surveys and PHANGS-ALMA.
Leroy A.K., Rosolowsky E., Usero A., Sandstrom K., Schinnerer E.,
Schruba A., Bolatto A.D., Sun J., Barnes A.T., Belfiore F., Bigiel F.,
den Brok J.S., Cao Y., Chiang I.-D., Chevance M., Dale D.A.,
Eibensteiner C., Faesi C.M., Glover S.C.O., Hughes A.,
Jimenez Donaire M.J., Klessen R.S., Koch E.W., Kruijssen J.M.D., Liu D.,
Meidt S.E., Pan H.-A., Pety J., Puschnig J., Querejeta M., Saito T.,
Sardone A., Watkins E.J., Weiss A., Williams T.G.
<Astrophys. J., 927, 149 (2022)>
=2022ApJ...927..149L 2022ApJ...927..149L
ADC_Keywords: Carbon monoxide; Molecular data; Interstellar medium;
Galaxies, nearby; Surveys
Keywords: Galaxies ; Interstellar molecules ; Interstellar medium ;
Molecular gas
Abstract:
We measure the low-J CO line ratios R21=CO(2-1)/CO(1-0),
R32=CO(3-2)/CO(2-1), and R31=CO(3-2)/CO(1-0) using whole-disk CO
maps of nearby galaxies. We draw CO(2-1) from PHANGS-ALMA, HERACLES,
and follow-up IRAM surveys; CO(1-0) from COMING and the Nobeyama CO
Atlas of Nearby Spiral Galaxies; and CO(3-2) from the James Clerk
Maxwell Telescope Nearby Galaxy Legacy Survey and Atacama Pathfinder
Experiment Large APEX Sub-Millimetre Array mapping. All together, this
yields 76, 47, and 29 maps of R21, R32, and R31 at 20"∼1.3kpc
resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high
stellar mass, log(M*/M☉)=10.25--11, and star formation rate
(SFR)=1-5M☉/yr, dominate the sample. We find galaxy-integrated
mean values and a 16%-84% range of R21=0.65(0.50-0.83),
R32=0.50(0.23-0.59), and R31=0.31(0.20-0.42). We identify weak
trends relating galaxy-integrated line ratios to properties expected
to correlate with excitation, including SFR/M* and SFR/LCO. Within
galaxies, we measure central enhancements with respect to the
galaxy-averaged value of ∼0.18-0.14+0.09dex for R21,
0.27-0.15+0.13dex for R31, and 0.08-0.09+0.11dex for R32.
All three line ratios anticorrelate with galactocentric radius and
positively correlate with the local SFR surface density and specific
SFR, and we provide approximate fits to these relations. The observed
ratios can be reasonably reproduced by models with low temperature,
moderate opacity, and moderate densities, in good agreement with
expectations for the cold interstellar medium. Because the line ratios
are expected to anticorrelate with the CO(1-0)-to-H2 conversion
factor, αCO1-0, these results have general implications for
the interpretation of CO emission from galaxies.
Description:
This paper presents new measurements of the CO(2-1)/CO(1-0),
CO(3-2)/CO(2-1), and CO(3-2)/CO(1-0) line ratios for nearby galaxies
(D<40Mpc, median ∼14Mpc) based on maps of CO emission from
Kuno+ (2007PASJ...59..117K 2007PASJ...59..117K), HERACLES (Leroy+ 2009ApJ...702..352L 2009ApJ...702..352L),
the James Clerk Maxwell Telescope (JCMT) Nearby Galaxy Legacy Survey
(NGLS; Wilson+ 2012MNRAS.424.3050W 2012MNRAS.424.3050W), the CO Multiline Imaging of
Nearby Galaxies (COMING) survey (Sorai+ 2019PASJ...71S..14S 2019PASJ...71S..14S),
PHANGS-ALMA (Leroy+ 2021, J/ApJS/257/43), new IRAM 30m CO(2-1)
observations (PI: A. Schruba), and new Atacama Pathfinder Experiment
(APEX) Large APEX Sub-Millimetre Array (LASMA) CO(3-2) observations
(PI: A. Weiss). We measure both resolved and integrated CO line ratios
using mapping surveys.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 114 152 Integrated CO line ratios and galaxy properties
table7.dat 55 11880 CO emission from multi-density models
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See also:
J/A+A/432/369 : Leiden Atomic & Molecular Database (LAMDA) (Schoeier+, 2005)
J/ApJ/724/1336 : An extragalactic 12CO J=3-2 survey (Mao+, 2010)
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010)
J/ApJ/772/107 : Giant molecular clouds in nearby gal. (Donovan Meyer+, 2013)
J/A+A/586/A50 : Central Molecular Zone H2CO temp. maps (Ginsburg+, 2016)
J/ApJ/846/159 : Interferometric CO obs. of CALIFA galaxies (Bolatto+, 2017)
J/A+A/604/A53 : ALLSMOG final DR. A new APEX CO survey (Cicone+, 2017)
J/ApJ/835/217 : Density distributions for mm-wave line ratios (Leroy+, 2017)
J/ApJS/233/22 : xCOLD GASS catalog (Saintonge+, 2017)
J/MNRAS/476/875 : xGASS catalog (Catinella+, 2018)
J/ApJ/858/90 : Radial profiles of 5 nearby galaxies (Gallagher+, 2018)
J/ApJ/860/172 : Cloud-scale molecular gas in 15 galaxies (Sun+, 2018)
J/ApJ/880/127 : EMPIRE: IRAM 30m dense gas survey (Jimenez-Donaire+, 2019)
J/ApJS/244/24 : A z=0 Multiwavelength Galaxy Synthesis. I. (Leroy+, 2019)
J/A+A/635/A131 : 12CO/13CO ratio in 126 nearby galaxy centers (Israel, 2020)
J/ApJ/897/122 : Rot. velocities for PHANGS sample of galaxies (Lang+, 2020)
J/ApJ/901/L8 : Molecular gas of 70 PHANGS-ALMA galaxies (Sun+, 2020)
J/MNRAS/500/1261 : Resolved molecular gas in nearby galaxies (Chown+, 2021)
J/ApJS/257/43 : PHANGS-ALMA: arcsecond CO imaging of gal. (Leroy+, 2021)
J/ApJ/909/56 : A galaxy sample with CO(2-1) & CO(5-4) (Liu+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Galaxy Name of the Galaxy
10- 12 A3 --- LRID Reported Line Ratio name (1)
14- 28 A15 --- Pair Shorthand for the pair of surveys
used to make the measurement (2)
30- 34 F5.2 Mpc Dist [2.8/40] Adopted distance (3)
36- 40 F5.2 [Msun] logMs [8.7/11.4] Log of stellar mass
42- 46 F5.2 [Msun/yr] logSFR [-1.1/1.7] Log of star formation
rate
48- 51 F4.2 [K.km.s-1.pc2] logLCO10 [7/9.8]? Log of best-estimate
CO(1-0) luminosity (4)
53- 56 F4.2 [K.km.s-1.pc2] e_logLCO10 [0/0.1]? Uncertainty in logLCO10
58- 61 F4.2 [K.km.s-1.pc2] logLCO10cal [0.1]? Calibration uncertainty in
logLCO10
63- 66 F4.2 [K.km.s-1.pc2] logLCO21 [6.5/9.6]? Log of best-estimate
CO(2-1) luminosity (4)
68- 71 F4.2 [K.km.s-1.pc2] e_logLCO21 [0.0/0.06]? Uncertainty in
logLCO21
73- 76 F4.2 [K.km.s-1.pc2] logLCO21cal [0.04/0.08]? Calibration
uncertainty in logLCO21
78- 81 F4.2 [K.km.s-1.pc2] logLCO32 [6.7/9]? Log of best-estimate
CO(3-2) luminosity (4)
83- 86 F4.2 [K.km.s-1.pc2] e_logLCO32 [0/0.07]? Uncertainty in logLCO32
88- 91 F4.2 [K.km.s-1.pc2] logLCO32cal [0.08]? Calibration uncertainty
in logLCO32
93 A1 --- l_logRAT [ULN] Limit flag for logRAT (5)
95- 99 F5.2 [-] logRAT [-2.2/0.11]? Log of measured
ratio LRID
101-104 F4.2 [-] e_logRAT [0/0.1]? Uncertainty in logRAT
106-109 F4.2 [-] logRATcal [0.09/0.13]? Calibration
uncertainty in logRAT
111-114 F4.2 [-] logRATcTot [0.09/0.16]? Total uncertainty in
logRAT
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Note (1): Line ratio as follows:
R31 = CO(3-2)/CO(1-0) ; 29 occurrences
R32 = CO(3-2)/CO(2-1) ; 47 occurrences
R21 = CO(2-1)/CO(1-0) ; 76 occurrences
Note (2): Survey as follows:
COMING = CO Multi-line Imaging of Nearby Galaxies
(Sorai+ 2019PASJ...71S..14S 2019PASJ...71S..14S)
NROATLAS = Nobeyama Radio Observatory (NRO) Atlas (Kuno+ 2007PASJ...59..117K 2007PASJ...59..117K)
PHANGS = Physics at High Angular resolution in Nearby Galaxies (PHANGS) -
ALMA (Leroy+ 2021, J/ApJS/257/43)
HERA = HERA CO-Line Extragalactic Survey (HERACLES;
Leroy+ 2009ApJ...702..352L 2009ApJ...702..352L & 2013AJ....146...19L 2013AJ....146...19L) and a follow-up
Virgo Cluster survey (PI: A. Schruba)
JCMT = The JCMT Nearby Galaxies Legacy Survey (Wilson+ 2012MNRAS.424.3050W 2012MNRAS.424.3050W)
supplemented by a few follow-up or archival JCMT observations
APEX = APEX Large APEX Sub-Millimetre Array (LASMA) mapping by
J. Puschnig et al. (in preparation)
Note (3): Adopted distance following Anand et al. (2021MNRAS.501.3621A 2021MNRAS.501.3621A)
Note (4): Best-estimate CO luminosity in the noted transition with aperture
corrections applied. For the luminosity we report only one best-estimate
value per galaxy. That is, this the single best estimate of LCO. We give
preference to COMING over the NRO Atlas and PHANGS-ALMA over IRAM HERA
data.
Note (5): In the case of limits, we report the 4 sigma upper [U] or lower limit
[L] as the value without uncertainties.
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.1 K tkin [10/50] Kinetic temperature (1)
6- 14 E9.3 cm-2.km-1.s coldv [1e+15/3.2e+18] Column of CO
per line width (1)
16- 23 F8.1 cm-1 n0 [31.6/100000] Mean collider H2 density (2)
25- 27 F3.1 [-] sigma [0.2/1.2] RMS width (2)
29- 37 E9.3 K.km.s-1.cm2 emis10 [2e-22/1.3e-19] Emissivity of H2 in the
CO(1-0) transition (3)
39- 43 F5.3 --- r21 [0.16/3.21] CO(2-1)/CO(1-0) line ratio
for the model (4)
45- 49 F5.3 --- r32 [0.046/1.6] CO(3-2)/CO(2-1) line ratio
for the model (4)
51- 55 F5.3 --- r31 [0.008/5] CO(3-2)/CO(1-0) line ratio for
the model (4)
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Note (1): Temperature and CO column per line width of all zones in the model.
Note (2): Mean collider H2 density and RMS width for the lognormal
distribution of densities in the model
Note (3): Assuming a fixed CO/H2 abundance of 1E-4
Note (4): See Leroy+ (2017, J/ApJ/835/217) for more details regarding
the calculation.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jan-2024