J/A+A/649/A39 xCOLD GASS and xGASS. Metallicity gradients (Lutz+, 2021)
xCOLD GASS and xGASS: Radial metallicity gradients and global properties on the
star-forming main sequence.
Lutz K.A., Saintonge A., Catinella B., Cortese L., Eisenhauer F., Kramer C.,
Moran S.M., Tacconi L.J., Vollmer B., Wang J.
<Astron. Astrophys. 649, A39 (2021)>
=2021A&A...649A..39L 2021A&A...649A..39L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; H I data ; Molecular data ; Spectroscopy
Keywords: ISM: abundances - galaxies: abundances - galaxies: evolution -
galaxies: ISM
Abstract:
The xGASS and xCOLD GASS surveys have measured the atomic (HI) and
molecular gas (H2) content of a large and representative sample of
nearby galaxies (redshift range of 0.01<z<0.05).
We present optical longslit spectra for a subset of the xGASS and
xCOLD GASS galaxies to investigate the correlation between radial
metallicity profiles and cold gas content. In addition to data from
Moran et al. (2012ApJ...745...66M 2012ApJ...745...66M), this paper presents new optical
spectra for 27 galaxies in the stellar mass range of
9.0≤logMstar[Msun]≤10.0.
The longslit spectra were taken along the major axis of the galaxies,
allowing us to obtain radial profiles of the gas-phase oxygen
abundance (12+log(O/H)). The slope of a linear fit to these radial
profiles is defined as the metallicity gradient. We investigated
correlations between these gradients and global galaxy properties,
such as star formation activity and gas content. In addition, we
examined the correlation of local metallicity measurements and the
global HI mass fraction.
We obtained two main results: (i) the local metallicity is correlated
with the global HI mass fraction, which is in good agreement with
previous results. A simple toy model suggests that this correlation
points towards a 'local gas regulator model'; (ii) the primary
driver of metallicity gradients appears to be stellar mass surface
density (as a proxy for morphology).
This work comprises one of the few systematic observational studies of
the influence of the cold gas on the chemical evolution of
star-forming galaxies, as considered via metallicity gradients and
local measurements of the gas-phase oxygen abundance. Our results
suggest that local density and local HI mass fraction are drivers of
chemical evolution and the gas-phase metallicity.
Description:
The optical longslit spectra of the 27 low-mass galaxies were obtained
with the EFOSC2 spectrograph at the ESO New Technology Telescope (NTT)
in La Silla, Chile in September 2012 and April 2013. The slit size was
1.5arcsec by 4arcmin and aligned along the major axis of each galaxy.
In order to measure all the strong emission lines required for
metallicity measurements, ranging in wavelength from [OII]372.7 nm to
Hα at 656.3nm, two observations of every galaxy were needed, one
for the bluer half of the spectrum (368.0nm to 550.0nm) and one for
the redder half (535.0nm to 720.0nm). The overlap was used to check
for consistency in flux calibration across the entire wavelength
range. Individual science exposures were observed for 900s. The total
exposure time varied according to the surface brightness of the
galaxy, but amounted on average to 3600 s per spectrum half. After
including a binning factor of 2, the image size is 1024 pixels by 1024
pixels. The spectral resolution is 0.123nm and 0.113nm in the red and
blue halves of the spectrum, respectively, which is approximately
equivalent to a velocity resolution of 59 and 74km/s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 409 106 List of studied sources
list.dat 132 27 List of fits spectra
fits/* . 27 Individual fits spectra
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See also:
J/ApJS/233/22 : xCOLD GASS catalog (Saintonge+, 2017)
J/MNRAS/476/875 : xGASS catalog (Catinella+, 2018)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- GASS GASS identifier (1)
8- 26 A19 --- SDSS SDSS identifier (1)
28- 38 F11.7 deg RAdeg Rigth ascension (J2000)
40- 48 F9.6 deg DEdeg Declination (J2000)
50- 54 F5.2 [Msun] logMstar Stellar mass (2)
56- 59 F4.2 [Msun/pc2] logmustar Stellar mass surface density (2)
61- 66 F6.2 mag NUV-r ?=-99.9 GALEX NUV - SDSS r colour (2)
68- 73 F6.2 [Msun] logMHI ?=-99.9 HI Mass (2)
75- 80 F6.2 [Msun] logMH2 ?=-99.9 H2 Mass (2)
82- 85 F4.2 --- c Concentration index (3)
87- 90 F4.2 --- a/b Axis ratio (3)
92- 96 F5.2 arcsec r90 90 per cent Petrosian radius, r band (3)
98-103 F6.2 arcsec r25 ?=-99.9 25mag/arcsec2 isophotal radius,
r band (3)
105-110 F6.2 arcsec reff ?=-99.9 Effective radius, r band (3)
112-117 F6.2 [-] logGFHI ?=-99.9 HI to stellar mass fraction (C18)
119-124 F6.2 [-] logGFH2 ?=-99.9 H2 to stellar mass fraction (C17)
126-132 F7.3 [Msun/yr] logSFR ?=-99.9 Star formation rate (2)
134-139 F6.2 [1/yr] logsSFR ?=-99.9 Specific star formation rate (2)
141-146 F6.2 --- defHI ?=-99.9 HI deficiency factor
148-153 F6.2 --- defH2 ?=-99.9 H2 deficiency factor
155-161 F7.3 --- Zgrad.LS-1 ?=-99.9 least-squares metallicity gradient
from full radial metallicity profile,
radius normalised by r90 (r band) (4)
163-169 F7.3 --- Zgrad.ML-1 ?=-99.9 maximum likelihood metallicity
gradient from full radial metallicity
profile, radius normalised by r90
(r band) (4)
171-177 F7.3 --- Zgrad.16-1 ?=-99.9 16th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by r90
(r band) (4)
179-185 F7.3 --- Zgrad.84-1 ?=-99.9 84th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by r90
(r band) (4)
187-193 F7.3 --- Zgrad.LS-2 ?=-99.9 least-squares metallicity gradient
from full radial metallicity profile,
radius normalised by r25 (r band) (4)
195-201 F7.3 --- Zgrad.ML-2 ?=-99.9 maximum likelihood metallicity
gradient from full radial metallicity
profile, radius normalised by r25
(r band) (4)
203-209 F7.3 --- Zgrad.16-2 ?=-99.9 16th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by r25
(r band) (4)
211-217 F7.3 --- Zgrad.84-2 ?=-99.9 84th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by r25
(r band) (4)
219-225 F7.3 --- Zgrad.LS-3 ?=-99.9 least-squares metallicity gradient
from full radial metallicity profile,
radius normalised by reff (r band) (4)
227-233 F7.3 --- Zgrad.ML-3 ?=-99.9 maximum likelihood metallicity
gradient from full radial metallicity
profile, radius normalised by reff
(r band) (4)
235-241 F7.3 --- Zgrad.16-3 ?=-99.9 16th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by reff
(r band) (4)
243-249 F7.3 --- Zgrad.84-3 ?=-99.9 84th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius normalised by reff
(r band) (4)
251-257 F7.3 --- Zgrad.LS-4 ?=-99.9 least-squares metallicity gradient
from full radial metallicity profile,
radius in kpc (4)
259-265 F7.3 --- Zgrad.ML-4 ?=-99.9 maximum likelihood metallicity
gradient from full radial metallicity
profile, radius in kpc (4)
267-273 F7.3 --- Zgrad.16-4 ?=-99.9 16th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius in kpc (4)
275-281 F7.3 --- Zgrad.84-4 ?=-99.9 84th percentile of metallicity
gradient PDF from full radial metallicity
profile, radius in kpc (4)
283-289 F7.3 --- Zgrad.LS-5 ?=-99.9 least-squares metallicity gradient
from radial metallicity profile without
central 0.5reff, radius normalised by r90
(r band) (4)
291-297 F7.3 --- Zgrad.ML-5 ?=-99.9 maximum likelihood metallicity
gradient from radial metallicity profile
without central 0.5reff,
radius normalised by r90 (r band) (4)
299-305 F7.3 --- Zgrad.16-5 ?=-99.9 16th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by r90 (r band) (4)
307-313 F7.3 --- Zgrad.84-5 ?=-99.9 84th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by r90 (r band) (4)
315-321 F7.3 --- Zgrad.LS-6 ?=-99.9 least-squares metallicity gradient
from radial metallicity profile without
central 0.5reff, radius normalised by r25
(r band) (4)
323-329 F7.3 --- Zgrad.ML-6 ?=-99.9 maximum likelihood metallicity
gradient from radial metallicity profile
without central 0.5reff,
radius normalised by r25 (r band) (4)
331-337 F7.3 --- Zgrad.16-6 ?=-99.9 16th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by r25 (r band) (4)
339-345 F7.3 --- Zgrad.84-6 ?=-99.9 84th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by r25 (r band) (4)
347-353 F7.3 --- Zgrad.LS-7 ?=-99.9 least-squares metallicity gradient
from radial metallicity profile without
central 0.5reff, radius normalised by
reff (r band) (4)
355-361 F7.3 --- Zgrad.ML-7 ?=-99.9 maximum likelihood metallicity
gradient from radial metallicity profile
without central 0.5reff,
radius normalised by reff (r band) (4)
363-369 F7.3 --- Zgrad.16-7 ?=-99.9 16th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by reff (r band) (4)
371-377 F7.3 --- Zgrad.84-7 ?=-99.9 84th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius normalised by reff (r band) (4)
379-385 F7.3 --- Zgrad.LS-8 ?=-99.9 least-squares metallicity gradient
from radial metallicity profile without
central 0.5reff, radius in kpc (4)
387-393 F7.3 --- Zgrad.ML-8 ?=-99.9 maximum likelihood metallicity
gradient from radial metallicity profile
without central 0.5reff,
radius in kpc (4)
395-401 F7.3 --- Zgrad.16-8 ?=-99.9 16th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius in kpc (4)
403-409 F7.3 --- Zgrad.84-8 ?=-99.9 84th percentile of metallicity
gradient PDF from radial metallicity
profile without central 0.5reff,
radius in kpc (4)
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Note (1): We use two identifiers for our galaxies, both are already available in
the dictionary of nomenclature: GASS and SDSS. Some of the galaxies with GASS
identifier might not yet have appeared with GASS identifier in the literature.
Note (2): data come from the xGASS (Catinella et al., 2018MNRAS.476..875C 2018MNRAS.476..875C,
Cat. J/MNRAS/476/875) and xCOLDGASS (Saintonge et al., 2017ApJS..233...22S 2017ApJS..233...22S,
Cat. J/ApJS/233/22) surveys.
Note (3): data come from the SDSS DR7 catalogue (Abazajian et al.,
2009ApJS..182..543A 2009ApJS..182..543A) and the compilation of galaxy properties in the
MPA-JHU catalogue (https://wwwmpa.mpa-garching.mpg.de/SDSS/DR7/).
Note (4): For each source we measured eight different gradients:
four gradients considering metallicity measurements within 0.5reff and
four gradients not considering these data points.
We described the galactocentric in four different ways:
normalised by reff, r90, r25 and in units of kpc.
These eight different approaches are labelled with "-n" in their column
names.
For each gradient measurement we provide four values in this table:
the gradient from a least squares fit (LS) and results from a MCMC estimation
of the gradient (ML: the maximum likelihood value, 16 and 84: the 16th and
84th percentile of the PDF of the gradient).
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 ---- GASS GASS identification number
8- 26 A19 --- SDSS SDSS designation (JHHMMSS.ss+DDMMSS.s)
28- 37 F10.6 deg RAdeg Right ascension (J2000)
39- 47 F9.6 deg DEdeg Declination (J2000)
49- 51 I3 --- Nx Number of pixels along X-axis
53- 56 I4 --- Ny Number of pixels along Y-axis
58- 80 A23 "datime" Obs.date Observation date
82- 85 I4 Kibyte size Size of FITS file
87-111 A25 --- FileName Name of FITS file, in subdirectory fits
113-132 A20 --- Title Title of the FITS file
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Acknowledgements:
Katharina Lutz, katharina.lutz(at)astro.unistra.fr
(End) Katharina Lutz [Obs. Strasbourg], Patricia Vannier [CDS] 18-Feb-2021