J/ApJ/923/240 Deeply buried nuclei in the LIRGs NGC4418. II. (Sakamoto+, 2021)
Deeply buried nuclei in the infrared-luminous galaxies NGC 4418 and Arp 220.
II. Line forests at λ=1.4-0.4mm and circumnuclear gas observed with ALMA.
Sakamoto K., Martin S., Wilner D.J., Aalto S., Evans A.S., Harada N.
<Astrophys. J., 923, 240 (2021)>
=2021ApJ...923..240S 2021ApJ...923..240S
ADC_Keywords: Active gal. nuclei; Galaxies, IR; Interstellar medium;
Spectra, millimetric/submm
Keywords: Active galaxies ; Interstellar medium ; Galaxy nuclei ;
Luminous infrared galaxies ; Galaxy winds ; Interstellar molecules ;
Galaxy kinematics
Abstract:
We present the line observations in our Atacama
Millimeter-Submillimeter Array imaging spectral scan toward three
deeply buried nuclei in NGC 4418 and Arp 220. We cover 67GHz in
frest=215-697GHz at about 0.2 (30, 80pc) resolution. All the nuclei
show dense line forests; we report our initial line identification
using 55 species. The line velocities generally indicate gas rotation
around each nucleus, tracing nuclear disks of ∼100pc in size. We
confirmed the counter-rotation of the nuclear disks in Arp 220 and
that of the nuclear disk and the galactic disk in NGC 4418. While the
brightest lines exceed 100K, most of the major lines and many 13C
isotopologues show absorption against even brighter continuum cores of
the nuclei. The lines with higher upper-level energies, including
those from vibrationally excited molecules, tend to arise from smaller
areas, indicating radially varying conditions in these nuclei. The
outflows from the two Arp 220 nuclei cause blueshifted line absorption
below the continuum level. The absorption mostly has small spatial
offsets from the continuum peaks to indicate the outflow orientations.
The bipolar outflow from the western nucleus is also imaged in
multiple emission lines, showing the extent of ∼1" (400pc). Redshifted
line absorption against the nucleus of NGC 4418 indicates either an
inward gas motion or a small collimated outflow slanted to the nuclear
disk. We also resolved some previous confusions due to line blending
and misidentification.
Description:
This paper presents line observations from our spectral scan toward
the three deeply buried nuclei in NGC 4418 and Arp 220. We scanned
67GHz from within frest=215-697GHz in the Atacama
Millimeter-Submillimeter Array (ALMA) Bands 6, 7, and 9.
We observed a single position in each galaxy. The FWHM of our primary
beam ranges between 24" and 8" in our observing frequencies. Our
target resolution was 0.2" and the achieved resolution ranged between
0.14" and 0.28", while the largest beam major axis was 0.35". The data
were recorded at the frequency resolution of 0.98MHz.
Details of the observations are in Paper I
(Sakamoto+ 2021ApJ...923..206S 2021ApJ...923..206S).
See Section 2.
Table 5 lists 255 lines in the frequency ranges of our observations.
It shows those lines having peak model intensities ≥10mJy/beam in
Band 7 and ≥3mJy/beam in Band 6; the thresholds are about 3σ in
our data. Our model spectral synthesis had no cutoffs. The table also
gives the velocity-integrated intensity in our model for each line.
see the Appendix.
Objects:
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RA (ICRS) DE Designation(s)
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12 26 54.62 +00 52 39.4 NGC 4418 = MCG+00-32-012
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 36 255 Initial spectral model of the nucleus of NGC 4418
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See also:
J/ApJS/73/359 : 1.49 GHz atlas of the IRAS bright galaxies (Condon+, 1990)
J/ApJ/378/65 : 8.4GHz observations of compact starbursts (Condon+ 1991)
J/ApJS/182/628 : Spitzer quasar and ULIRG evolution study (Veilleux+, 2009)
J/ApJ/799/10 : Arp 220 6 and 33GHz images (Barcos-Munoz+, 2015)
J/A+A/582/A91 : NGC 4418 ALMA mm-wave spectral scan (Costagliola+, 2015)
J/A+A/590/A25 : Arp 220 HCN and HCO+ data cubes (Martin+, 2016)
J/A+A/593/A86 : Arp 220 LOFAR radio images at 150MHz (Varenius+, 2016)
J/ApJS/233/11 : Cyanoacetylene (HC3N) infrared spectrum (Bizzocchi+, 2017)
J/A+A/607/A43 : NGC 4418/VV 655 HI images (Varenius+, 2017)
J/A+A/623/A173 : SNe/SNRs in starburst galaxy Arp 220 (Varenius+, 2019)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 GHz Frest [216.27/366.24] Rest frequency
11- 15 F5.1 mJy/beam Inu [3/832] Peak line intensity
17- 21 F5.1 Jy.km/s/beam S [0.4/192] Velocity integrated line intensity
23- 36 A14 --- Species Species with vibrational states when
necessary
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History:
From electronic version of the journal
References:
Sakamoto et al. Paper I. 2021ApJ...923..206S 2021ApJ...923..206S
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Jun-2023