J/ApJ/915/L3 Molecular clouds from NOEMA CO(1-0) obs. in M82 (Krieger+, 2021)
NOEMA high-fidelity imaging of the molecular gas in and around M82.
Krieger N., Walter F., Bolatto A.D., Guillard P., Lehnert M., Leroy A.K.,
Pety J., Emig K.L., Levy R.C., Krips M., Rix H.-W., Salak D., Weiss A.,
Veilleux S.
<Astrophys. J., 915, L3 (2021)>
=2021ApJ...915L...3K 2021ApJ...915L...3K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby; Molecular clouds; Carbon monoxide;
Molecular data
Keywords: Molecular gas; Molecular clouds; Tidal tails; Galactic winds
Interstellar medium; Starburst galaxies
Abstract:
We present a 154 pointing IRAM NOEMA mosaic of the CO(1-0) line
emission in and around the nearby starburst galaxy M82. The
observations, complemented by zero-spacing observations, reach a
spatial resolution of ∼30 pc (∼1.9") at 5.0km/s spectral resolution,
sufficient to resolve the molecular gas in the central starburst disk,
the outflow, and the tidal streamers. The resulting moment and peak
brightness maps show a striking amount of structure. Using a clump
decomposition algorithm, we analyze the physical properties (e.g.,
radii R, line widths σ, and masses M) of ∼2000 molecular clouds.
To first order, the clouds' properties are very similar, irrespective
of their environment. This also holds for the size-line width
relations of the clouds. The distribution of clouds in the
σ2/R versus column density Σ space suggests that
external pressure does not play a significant role in setting their
physical parameters in the outflow and streamers. We find that the
clouds in the streamers stay approximately constant in size (R∼50pc)
and mass (M∼105M☉) and do not vary with their projected
distance from M82's center. The clouds in the outflow, on the other
hand, appear to decrease in size and mass with distance toward the
southern outflow. The reduction in the molecular gas luminosity could
be indicative of cloud evaporation of embedded clouds in the hot
outflow.
Description:
The Northern Extended Millimeter Array (NOEMA) mosaic covers an area
of ∼25arcmin2 over 7.7' (7.9kpc) along the major axis and out to
±2.8' (±2.9kpc) along the minor axis of M82. The mosaic consists
of 154 pointings with a hexagonal arrangement with half-width primary
beam spacing (21.5") to achieve an approximately uniform sensitivity
across the field of view. While the main focus of the observations is
the rotational ground-state transition of carbon monoxide (CO(1-0) at
νrest=115.271GHz), the wide bandwidth correlator at NOEMA also
covers other molecular lines, such as 13CO(1-0), CS(2-1), or CN(1-0)
that are not discussed in this paper.
The NOEMA observations were carried out under project ID W18BY between
2019 March and 2020 January.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
09 55 52.42 +69 40 46.9 M82 = NAME Cigar Galaxy
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 91 1746 Cloud catalog
--------------------------------------------------------------------------------
See also:
J/A+A/293/703 : Outflow in M82 halo (McKeith+, 1995)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJ/899/158 : Gas structure comparison; NGC253 and Milky Way (Krieger+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1891] Cloud index number
6- 13 F8.4 deg RAdeg [148.8/149.2] Cloud center right ascension
(J2000)
15- 21 F7.4 deg DEdeg [69.6/69.8] Cloud center declination (J2000)
23- 28 F6.1 km/s Vel [-185.4/460.5] Cloud center velocity
30- 36 E7.1 kpc Rcenter [0.039/4.1] Projected cloud distance (1)
38- 44 E7.1 pc Rad [5.4/180]? Projected cloud radius;
see Section 4.2.1
46- 52 E7.1 km/s sigma [1.3/36]? Cloud line width;
see Section 4.2.2
54- 61 E8.2 Msun Mass [359/5.1e+7] Cloud mass (2)
63- 69 E7.1 Msun/pc2 Sigma [1/570]? Cloud surface density (2)
71- 77 E7.1 K.km/pc2 mu [0.017/11] Cloud surface brightness
79- 91 A13 --- Region Region the cloud belongs to;
see Section 3.2 ("disk", "outflow_north",
"outflow_south", "streamer_east" or
"streamer_west")
--------------------------------------------------------------------------------
Note (1): From M82 center at (RA,DE) = (09:55:52.72, 69:40:45.7).
Note (2): Assuming a starburst conversion factor of
αCO = 1.0 MSun (K km/s pc2)-1.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Feb-2024