J/A+A/645/A97 ALMA cube and GMC catalog of J1023+1952 (Querejeta+, 2021)
ALMA resolves giant molecular clouds in a tidal dwarf galaxy.
Querejeta M., Lelli F., Schinnerer E., Colombo D., Lisenfeld U.,
Mundell C.G., Bigiel F., Garcia-Burillo S., Herrera C.N., Hughes A.,
Kruijssen J.M.D., Meidt S., Moore T.J.T., Pety J., Rigby A.J.
<Astron. Astrophys. 645, A97 (2021)>
=2021A&A...645A..97Q 2021A&A...645A..97Q (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, peculiar ; Molecular clouds
Keywords: galaxies: dwarf - galaxies: interactions -
galaxies: star formation - galaxies: ISM -
galaxies: kinematics and dynamics
Abstract:
Tidal dwarf galaxies (TDGs) are gravitationally bound condensations of
gas and stars that formed during galaxy interactions. Here we present
multi-configuration ALMA observations of J1023+1952, a TDG in the
interacting system Arp 94, where we resolved CO(2-1) emission down to
giant molecular clouds (GMCs) at 0.64" ∼45pc resolution. We find a
remarkably high fraction of extended molecular emission (∼80-90%),
which is filtered out by the interferometer and likely traces diffuse
gas. We detect 111 GMCs that give a similar mass spectrum as those in
the Milky Way and other nearby galaxies (a truncated power law with a
slope of -1.76±0.13). We also study Larson's laws over the available
dynamic range of GMC properties (∼2dex in mass and ∼1dex in size):
GMCs follow the size-mass relation of the Milky Way, but their
velocity dispersion is higher such that the size-linewidth and virial
relations appear super-linear, deviating from the canonical values.
The global molecular-to-atomic gas ratio is very high (∼1) while the
CO(2-1)/CO(1-0) ratio is quite low (∼0.5), and both quantities vary
from north to south. Star formation predominantly takes place in the
south of the TDG, where we observe projected offsets between GMCs and
young stellar clusters ranging from ∼50pc to ∼200pc; the largest
offsets correspond to the oldest knots, as seen in other galaxies. In
the quiescent north, we find more molecular clouds and a higher
molecular-to-atomic gas ratio (∼1.5); atomic and diffuse molecular gas
also have a higher velocity dispersion there. Overall, the
organisation of the molecular interstellar medium in this TDG is quite
different from other types of galaxies on large scales, but the
properties of GMCs seem fairly similar, pointing to near universality
of the star-formation process on small scales.
Description:
ALMA CO(2-1) cube of J1023+1952, a tidal dwarf galaxy (TDG) that
overlaps in projection with the spiral NGC 3227, in the system Arp 94.
The observations cover the whole extent of the TDG (∼64"x43") at a
resolution of 0.64" (45pc for a distance of 14.5Mpc). The ALMA cube
combines observations from the 12m-array and the Atacama Compact Array
(7-m array and total power) from project 2016.1.00648.S (PI: M.
Querejeta). We also provide the mask that we used to exclude emission
from the background spiral NGC 3227, which lies at lower velocities.
The mask was based on continuity in HI emission at 30" resolution. See
the paper for more details. Table A3 is the GMC catalogue produced
with CPROPS as explained in the paper.
Objects:
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RA (2000) DE Designation(s)
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10 23 26.25 +19 51 58.8 J1023+1952 = [MJL2004b] J1023+1952
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea3.dat 95 111 Measurements for Nyquist-sampled apertures
list.dat 140 2 List of fits datacubes
fits/* . 2 Individual fits datacubes
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- CloudID [1/111] Number of GMC from CPROPS
5- 12 F8.4 deg RAdeg Right ascension (J2000)
14- 21 F8.5 deg DEdeg Declination (J2000)
23- 26 F4.2 --- a/b GMC ellipse axis ratio (a/b)
28- 32 F5.1 deg PA GMC ellipse position angle
34- 38 F5.1 pc R ?=- GMC radius
40- 43 F4.1 pc e_R ?=- Uncertainty GMC radius
45- 48 F4.1 km/s sigmaV GMC velocity dispersion
50- 52 F3.1 km/s e_sigmaV Uncertainty GMC velocity dispersion
54- 58 F5.3 K Tpeak GMC peak temperature
60- 65 I6 K.km/s.pc2 LCO GMC CO luminosity
67- 72 I6 K.km/s.pc2 e_LCO Uncertainty GMC CO luminosity
74- 77 I4 Msun Mlum GMC luminous mass
79- 81 I3 Msun e_Mlum Uncertainty GMC luminous mass
83- 87 I5 Msun Mvir ?=- GMC virial mass
89- 93 I5 Msun e_Mvir ?=- Uncertainty GMC virial mass
95 A1 --- Environm [N/S] Environment in TDG: N=north, S=south
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 32 I3 --- Nz Number of slices
34- 59 A26 "datime" Obs.date Observation date
61- 71 E11.6 m/s bVELO Lower value of VELO interval
73- 83 E11.6 m/s BVELO Upper value of VELO interval
85- 95 E11.6 m/s dVELO VELO resolution
97-103 I7 Kibyte size Size of FITS file
105-113 A9 --- FileName Name of FITS file, in subdirectory fits
115-140 A26 --- Title Title of the FITS file
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Acknowledgements:
Miguel Querejeta, m.querejeta(at)oan.es
(End) Patricia Vannier [CDS] 04-Nov-2020