J/A+A/660/A83 NGC1068 I-HCN(1-0) and I-HCO+(1-0) maps (Sanchez-Garcia+, 2022)
Spatially resolved star-formation relations of dense molecular gas in NGC 1068.
Sanchez-Garcia M., Garcia-Burillo S., Pereira-Santaella M., Colina L.,
Usero A., Querejeta M., Alonso-Herrero A., Fuente A.
<Astron. Astrophys. 660, A83 (2022)>
=2022A&A...660A..83S 2022A&A...660A..83S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, Seyfert ; Radio lines
Keywords: galaxies: individual: NGC 1068 - galaxies: Seyfert -
galaxies: star formation
Abstract:
The current understanding of star formation (SF) contemplates that the
regulation of this phenomenon in galaxy disks reflects
a complex balance between processes that operate in molecular gas on
local cloud-scales but also on global disk-scales.
We analyse the influence of the dynamical environment on the SF
relations of the dense molecular gas in the starburst (SB) ring of the
Seyfert 2 galaxy NGC 1068.
We used ALMA to image the emission of the 1-0 transitions of HCN and
HCO+, which trace dense molecular gas in the r∼1.3kpc SB ring of
NGC 1068, with a resolution of 56pc. We also used ancillary data of
CO(1-0), as well as CO(3-2) and its underlying continuum emission at
the resolutions of 100pc and 40pc, respectively. These observations
allow us to probe a wide range of molecular gas densities
(nH2∼103-5cm-3). The SF rate (SFR) in the SB ring of NGC 1068 is
derived from Paα line emission imaged by HST/NICMOS. We analysed
how different formulations of SF relations change depending on the
adopted aperture sizes and on the choice of molecular gas tracer.
The scatter in the Kennicutt-Schmidt relation, linking the SFR density
(SFR) with the (dense) molecular gas surface density ({SIGMA}dense),
is about a factor of two to three lower for the HCN and HCO+ lines
compared to that derived from CO(1-0) for a common aperture.
Correlations lose statistical significance below a critical spatial
scale 300-400pc for all gas tracers. The efficiency of SF of the dense
molecular gas, defined as SFEdense={SIGMA}SFR/{SIGMA}dense_, shows
a scattered distribution as a function of the HCN luminosity (L0(HCN))
around a mean value of ~=0.01Myr-1. An alternative prescription for
SF relations, which includes the dependence of SFEdense on the
combination of {SIGMA}dense and the velocity dispersion (σ),
resolves the degeneracy associated with the SFEdense-L'(HCN) plot.
The SFEdense values show a positive trend with the boundedness of
the gas, measured by the parameter b={SIGMA}dense/σ2.We
identify two branches in the SFEdense-b plot that correspond to two
dynamical environments within the SB ring, which are defined by their
proximity to the region where the spiral structure is connected to the
stellar bar. This region corresponds to the crossing of two
overlapping density wave resonances, where an increased rate of
cloud-cloud collisions would favour an enhanced compression of
molecular gas.
These results suggest that galactic dynamics plays a major role in the
efficiency of the gas conversion into stars. Our work adds supporting
evidence that density-threshold star formation models, which argue
that the SFEdense should be roughly constant, fail to account for
spatially resolved SF relations of dense gas in the SB ring of NGC
1068.
Description:
The velocity-integrated intensity maps obtained in the HCN(1-0), and
HCO+(1-0) molecular lines in the Seyfert 2 galaxy NGC1068 (M77) by
the Atacama Large Millimeter Array (ALMA). The interferometric
observations were carried out in August 2015. The datasets presented
here were imaged with synthesised beams of 1"x0.6"@PA=69° for both
lines. The images are in FITS-format. The intensity scale is in
Jy.km/s/beam. See the paper for further details.
Objects:
-------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------
02 42 40.709 -00 00 47.94 M77 = NGC 1068
-------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 101 2 List of fits images
fits/* . 2 Individual fits images
--------------------------------------------------------------------------------
See also:
J/A+A/549/A39 : A 3mm molecular line survey of NGC1068 (Aladro+, 2013)
J/A+A/565/A71 : NGC1068 MIDI/VLTI observations (Lopez-Gonzaga+, 2014)
J/A+A/602/A78 : NGC1068 interferometric mid-IR measurements
(Lopez-Gonzaga+, 2017)
J/A+A/632/A61 : NGC1068 CO and HCO images (Garcia-Burillo+, 2019)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
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- 31 I4 Kibyte size Size of FITS file
33- 67 A35 --- FileName Name of FITS file, in subdirectory fits
69-101 A33 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Maria Sanchez Garcia, mariasg(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 29-Jan-2022