J/A+A/625/A19 33 GHz continuum map of M51 (Querejeta+, 2019)
Dense gas is not enough: environmental variations in the star formation
efficiency of dense molecular gas at 100pc scales in M51.
Querejeta M., Schinnerer E., Schruba A., Murphy E., Meidt S., Usero A.,
Leroy A. K., Pety J., Bigiel F., Chevance M., Faesi C. M., Gallagher M.,
Garcia-Burillo S., Glover S. C. O., Hygate A. P. S., Jimenez-Donaire M. J.,
Kruijssen J. M. D., Momjian E., Rosolowsky E., Utomo D.
<Astron. Astrophys. 625, A19 (2019)>
=2019A&A...625A..19Q 2019A&A...625A..19Q (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, radio ; Molecular clouds
Keywords: galaxies: individual: NGC 5194 - galaxies: ISM -
galaxies: star formation - galaxies: structure
Abstract:
It remains unclear what sets the efficiency with which molecular gas
transforms into stars. Here we present a new VLA map of the spiral
galaxy M51 in 33GHz radio continuum, an extinction-free tracer of star
formation, at 3" scales (∼100pc). We combined this map with
interferometric PdBI/NOEMA observations of CO(1-0) and HCN(1-0) at
matched resolution for three regions in M51 (central molecular ring,
northern and southern spiral arm segments). While our measurements
roughly fall on the well-known correlation between total infrared and
HCN luminosity, bridging the gap between Galactic and extragalactic
observations, we find systematic offsets from that relation for
different dynamical environments probed in M51, e.g. the southern arm
segment is more quiescent due to low star formation efficiency (SFE)
of the dense gas, despite having a high dense gas fraction. Combining
our results with measurements from the literature at 100pc scales, we
find that the SFE of the dense gas and the dense gas fraction
anti-correlate and correlate, respectively, with the local stellar
mass surface density. This is consistent with previous kpc-scale
studies. In addition, we find a significant anti-correlation between
the SFE and velocity dispersion of the dense gas. Finally, we confirm
that a correlation also holds between star formation rate surface
density and the dense gas fraction, but it is not stronger than the
correlation with dense gas surface density. Our results are hard to
reconcile with models relying on a universal gas density threshold for
star formation and suggest that turbulence and galactic dynamics play
a major role in setting how efficiently dense gas converts into stars.
Description:
33GHz radio continuum map of the galaxy M51 (NGC5194) from the Karl
G. Jansky Very Large Array (VLA), covering the central 300"x250"
(∼11x9kpc). The interferometric observations were carried out between
August 2014 and January 2015 in C and D configurations. The dataset
presented here was imaged with a taper that resulted in a synthesised
beam of 2.94"x2.67"; the map was then convolved with a round Gaussian
beam of 3". See the paper for more details.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
13 29 52.70 +47 11 42.9 M51 = NGC 5194
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 122 27 Measurements for apertures on HCN peaks
tablea2.dat 122 4280 Measurements for Nyquist-sampled apertures
list.dat 88 1 Information of fits datacube
fits/* . 1 Datacube
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See also:
J/A+A/568/A74 : Low-frequency (115-175MHz) image of M51 (Mulcahy+, 2014)
J/A+A/592/A123 : M51 total intensity image at 333MHz (Mulcahy+, 2016)
J/A+A/593/A118 : HCN(1-0) cube for the nucleus of M51 (Querejeta+, 2016)
J/A+A/617/A136 : LOFAR M51 field low-frequency polarized sources
(Horellou+, 2018)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Region in M51 (north, ring, south)
10- 17 F8.4 deg RAdeg Right ascension (J2000)
19- 26 F8.5 deg DEdeg Declination (J2000)
28- 31 I4 Msun/pc2 SigStar Stellar mass surface density
33- 36 I4 Msun/pc2 e_SigStar Uncertainty stellar mass surface density
38- 42 F5.1 10+6Lsun TIR Total Infrared Luminosity (TIR)
44- 47 F4.1 10+6Lsun e_TIR Uncertainty TIR
49- 53 F5.1 uJy F33GHz 33GHz Spectral Flux Density
55- 57 F3.1 uJy e_F33GHz Uncertainty 33GHz Flux Density
59- 64 F6.1 % tfrac Thermal fraction at 33GHz
66- 69 F4.1 % e_tfrac Uncertainty thermal fraction 33GHz
71- 75 F5.2 Msun/Myr/pc2 SigSFR Star formation rate surface density
77- 80 F4.2 Msun/Myr/pc2 e_SigSFR Uncertainty SFR surface density
82- 86 F5.2 K.km/s IHCN HCN(1-0) intensity
88- 91 F4.2 K.km/s e_IHCN Uncertainty HCN(1-0) intensity
93- 97 F5.1 K.km/s ICO ?=- CO(1-0) intensity
99-102 F4.1 K.km/s e_ICO ?=- Uncertainty CO(1-0) intensity
104-107 F4.1 km/s sigHCN ?=- HCN(1-0) velocity dispersion
109-111 F3.1 km/s e_sigHCN ?=- Uncertainty HCN(1-0) velocity
dispersion
113-117 F5.2 km/s sigCO ?=- CO(1-0) velocity dispersion
119-122 F4.2 km/s e_sigCO ?=- Uncertainty CO(1-0) velocity
dispersion
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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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 46 A19 "datime" Obs.date Observation date
48- 51 I4 Kibyte size Size of FITS file
53- 60 A8 --- FileName Name of FITS file, in subdirectory fits
62- 88 A27 --- Title Title of the FITS file
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Acknowledgements:
Miguel Querejeta, mquereje(at)eso.org
(End) Patricia Vannier [CDS] 13-Mar-2019