J/ApJ/954/148 ALMA obs. of HCN and HCO+ for 12 (U)LIRGs (Imanishi+, 2023)
ALMA 0.5 kpc resolution spatially resolved investigations of nuclear dense
molecular gas properties in nearby ultraluminous infrared galaxies based on HCN
and HCO.
Imanishi M., Baba S., Nakanishi K., Izumi T.
<Astrophys. J., 954, 148 (2023)>
=2023ApJ...954..148I 2023ApJ...954..148I
ADC_Keywords: Galaxies, IR; Molecular data; Interferometry; Active gal. nuclei;
Millimetric/submm sources; Redshifts; Space velocities
Keywords: Ultraluminous infrared galaxies ; Luminous infrared galaxies ;
Supermassive black holes ; Active galactic nuclei ; Galaxy mergers ;
Starburst galaxies ; Molecular spectroscopy ; Molecular gas ;
Millimeter astronomy ; Submillimeter astronomy ;
Radio interferometers ; Active galaxies
Abstract:
We present the results of our ALMA≲0.5kpc resolution dense molecular
line (HCN and HCO+J=2-1, J=3-2, and J=4-3) observations of 12 nearby
(ultra)luminous infrared galaxies ([U]LIRGs). After matching beam
sizes of all molecular line data to the same values in all (U)LIRGs,
we derive molecular line flux ratios by extracting spectra in the
central 0.5, 1, and 2kpc circular regions and in 0.5-1 and 1-2kpc
annular regions. Based on non-local thermal equilibrium model
calculations, we quantitatively confirm that the innermost (≲0.5kpc)
molecular gas is very dense (≳105cm-3) and warm ({≳300K) in
ULIRGs, and that in one LIRG, it is also modestly dense (104-5cm-3)
and warm (∼100K). We then investigate the spatial variation of the
HCN-to-HCO+ flux ratios and high-J to low-J flux ratios of HCN and
HCO+. A subtle sign of a decreasing trend in these ratios from the
innermost (≲0.5kpc) to the outer nuclear (0.5-2kpc) region is
discernible in a significant fraction of the observed ULIRGs. For two
ULIRGS hosting an active galactic nucleus (AGN), which display the
trend most clearly, we find based on a Bayesian approach that the
HCN-to-HCO+ abundance ratio and gas kinetic temperature systematically
increase from the outer nuclear to the innermost region. We suggest
that this trend comes from potential AGN effects because no such
spatial variation is found in a starburst-dominated LIRG.
Description:
Our HCN and HCO+ J=2-1 and J=4-3 observations of 11 ultraluminous
infrared galaxies (ULIRGs) and for one starburst-dominated LIRG
NGC1614 were conducted in our ALMA Cycle 7 program 2019.1.00027.S
(PI=Imanishi M.). Observations span 2021-May-15 to 2021-Jul-12.
See Section 3.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 107 12 Basic properties of the observed (Ultra)luminous
infrared galaxies
table9.dat 129 318 *Gaussian fit of emission lines
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Note on table9.dat: When the Gaussian values are blank, no Gaussian fit was
applied because no emission line signature was in the spectrum.
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See also:
J/ApJ/522/113 : 1Jy IRAS galaxies optical spectroscopy (Veilleux+, 1999)
J/AJ/126/1607 : IRAS Revised Bright Galaxy Sample (Sanders+, 2003)
J/ApJS/184/230 : Spitzer high-res. MIR spectral atlas (Bernard-Salas+, 2009)
J/ApJS/182/628 : Spitzer quasar and ULIRG evolution study (Veilleux+, 2009)
J/ApJ/723/993 : Spatial extent of (U)LIRGs in MIR. I. (Diaz-Santos+, 2010)
J/MNRAS/405/2505 : Nuclear activity in ULIRGs (Nardini+, 2010)
J/A+A/579/A101 : 3mm molecular line survey of 8 AGN (Aladro+, 2015)
J/ApJ/829/93 : CO, [CI] & [NII] lines from Herschel sp. (Kamenetzky+, 2016)
J/A+A/590/A25 : Arp 220 HCN and HCO+ data cubes (Martin+, 2016)
J/ApJS/230/1 : Herschel SPIRE 194-671um survey of GOALS LIRGs (Lu+, 2017)
J/ApJ/923/240 : Deeply buried nuclei in NGC4418. II. (Sakamoto+, 2021)
J/ApJS/257/57 : Cold molecular gas in merger remnants. II. (Ueda+, 2021)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Galaxy name
17 A1 --- f_Name Flag on Name (1)
19- 24 F6.4 --- z [0.016/0.15] Redshift adopted from I16 (2)
26- 28 I3 Mpc Dist [68/655] Luminosity distance, dL
30- 33 F4.2 kpc/arcsec Scale [0.3/2.5] Physical scale
35 A1 --- l_F12um Limit flag on F12um
37- 40 F4.2 Jy F12um [0.05/1.4] IRAS flux at 12um (3)
42 A1 --- l_F25um Limit flag on F25um
44- 47 F4.2 Jy F25um [0.14/7.5] IRAS flux at 25um (3)
49- 53 F5.2 Jy F60um [1.38/32.12] IRAS flux at 60um (3)
55- 59 F5.2 Jy F100um [1.42/34.32] IRAS flux at 100um (3)
61- 64 F4.1 [Lsun] logLIR [11.7/12.6] Log of the infrared 8-1000um
luminosity (4)
66- 70 A5 --- OClass Optical spectroscopic classification (5)
72 A1 --- l_AGNir Limit flag on AGNir
74- 78 F5.2 % AGNir [0.05/88] Infrared spectroscopically
estimated bolometric contribution of AGN
(6)
80- 81 I2 % e_AGNir [2/10]? Lower uncertainty on AGNir
83 I1 % E_AGNir [6/6]? Upper uncertainty on AGNir
85- 107 A23 --- Notes Notes (7)
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Note (1): Flag on IRAS 12112+0305 as follows:
a = Also known as IRAS 04315-0840. This is a LIRG that is classified as
starburst dominated through various spectroscopic observations
(e.g., Brandl+ 2006ApJ...653.1129B 2006ApJ...653.1129B; Bernard-Salas+ 2009, J/ApJS/184/230;
Imanishi+ 2010ApJ...721.1233I 2010ApJ...721.1233I; Pereira-Santaella+ 2015MNRAS.454.3679P 2015MNRAS.454.3679P).
b = IRAS 12112+0305 is listed separately because we have only one
J-transition line data with a resolution of <∼0.5kpc.
Note (2): Redshift adopted from ALMA dense molecular line data
(Imanishi+ 2016AJ....152..218I 2016AJ....152..218I), which are slightly different from
optically derived data (Kim & Sanders 1998ApJS..119...41K 1998ApJS..119...41K) in some cases.
Note (3): IRAS fluxes at 12um, 25um, 60um, and 100um taken from
Kim & Sanders (1998ApJS..119...41K 1998ApJS..119...41K) or Sanders+ (2003, J/AJ/126/1607) or
the IRAS Faint Source Catalog (FSC, II/156).
Note (4): Decimal logarithm of the infrared (8-1000um) luminosity, calculated
with LIR=2.1x1039xD(Mpc)2x(13.48xF12+5.16xF25+2.58xF60+F100)erg/s
(Sanders & Mirabel 1996ARA&A..34..749S 1996ARA&A..34..749S).
Note (5): Optical spectroscopic classification by
Veilleux+ (1999, J/ApJ/522/113) or Veilleux+ (1995ApJS...98..171V 1995ApJS...98..171V).
"LINER" and "H II" refer to the LINER and HII-region, respectively.
Note (6): Infrared spectroscopically estimated bolometric contribution of AGN
in percent by Nardini+ (2010, J/MNRAS/405/2505) for all ULIRGs and by
Pereira-Santaella+ (2015MNRAS.454.3679P 2015MNRAS.454.3679P) for the LIRG NGC 1614.
Note (7): "Y" means the presence of signatures of optically elusive but
intrinsically luminous buried AGNs. All ULIRGs show elevated (≳1)
HCN-to-HCO+ J=3-2 flux ratios at ∼1.3mm (Imanishi+ 2019ApJS..241...19I 2019ApJS..241...19I),
which are possible signatures of luminous AGNs
(e.g., Imanishi+ 2016AJ....152..218I 2016AJ....152..218I). Other representative references
for the AGN signatures in the infrared 3-40um and/or (sub)millimeter
spectra:
(b) = Imanishi+ 2007ApJS..171...72I 2007ApJS..171...72I
(c) = Veilleux+ 2009, J/ApJS/182/628
(d) = Imanishi+ 2006ApJ...637..114I 2006ApJ...637..114I
(e) = Imanishi+ 2010ApJ...721.1233I 2010ApJ...721.1233I
(f) = Imanishi+ 2018ApJ...856..143I 2018ApJ...856..143I
(g) = Imanishi+ 2016AJ....152..218I 2016AJ....152..218I
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Galaxy name
17- 28 A12 --- Region Region identifier
30- 37 A8 --- Mol Molecule identifier
39- 43 A5 --- Line Line identifier
45- 49 I5 km/s Vel1 [4653/42089]? First Gaussian fit optical LSR
velocity
51- 53 I3 km/s e_Vel1 [3/231]? Uncertainty in Vel1 (1)
54 A1 --- f_Vel1 [b] Indicates Vel1 is a fixed value
56- 60 I5 km/s Vel2 [4840/42294]? Second Gaussian fit optical LSR
velocity
62- 64 I3 km/s e_Vel2 [5/130]? Uncertainty in Vel2 (1)
66- 70 F5.2 mJy Peak1 [0.47/55.4]? First Gaussian fit peak flux
density
72- 75 F4.2 mJy e_Peak1 [0.09/4]? Uncertainty in Peak1 (1)
77- 81 F5.1 mJy Peak2 [-17.3/25.3]? Second Gaussian fit peak flux
density
83- 85 F3.1 mJy e_Peak2 [0.1/3]? Uncertainty in Peak2 (1)
87 A1 --- f_Peak2 [a] Flag on Peak2 (2)
89- 92 I4 km/s FWHM1 [54/1145]? First Gaussian fit Full-Width at
Half-Maximum value
94- 96 I3 km/s e_FWHM1 [6/782]? Uncertainty in FWHM1 (1)
97 A1 --- f_FWHM1 [b] Indicates FWHM1 is a fixed value
99- 101 I3 km/s FWHM2 [46/743]? Second Gaussian fit Full-Width at
Half-Maximum value
103- 105 I3 km/s e_FWHM2 [16/204]? Uncertainty in FWHM2 (1)
106 A1 --- f_FWHM2 [b] Indicates FWHM2 is a fixed value
108- 112 F5.2 Jy.km/s Flux [0.2/19.6]? Gaussian fit velocity-integrated
flux (3)
114- 117 F4.2 Jy.km/s e_Flux [0.05/4]? Uncertainty in Flux (1)
119- 129 A11 --- f_Flux Flag on Flux (4)
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Note (1): Only Gaussian fitting error (statistical uncertainty) is considered.
Note (2):
a = We adopt one broad Gaussian emission and one narrow Gaussian absorption
components, because negative signals below the continuum level at the
HCO+ central dip, observed in IRAS 00091-0738 (Figures 2 and 3), cannot
be reproduced by two Gaussian emission components. This flux estimate
agrees within ∼10% with that based on two Gaussian emission components.
Note (3): When fitting results of two Gaussian components are adopted, fluxes
of the two components are added.
Note (4): The "(<3σ)" indicates that the flux divided by the uncertainty
is less than 3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Nov-2025