J/MNRAS/502/4815 Very young galaxies in the local Universe (Trevisan+, 2021)
The properties and environment of very young galaxies in the local Universe.
Trevisan M., Mamon G.A., Thuan T.X., Ferrari F., Pilyugin L.S., Ranjan A.
<Mon. Not. R. Astron. Soc., 502, 4815-4841 (2021)>
=2021MNRAS.502.4815T 2021MNRAS.502.4815T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Morphology
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: stellar content
Abstract:
In the local Universe, there are a handful of dwarf compact
star-forming galaxies with extremely low oxygen abundances. It has
been proposed that they are young, having formed a large fraction of
their stellar mass during their last few hundred Myr. However, little
is known about the fraction of young stellar populations in more
massive galaxies. In a previous article, we analysed 404000 Sloan
Digital Sky Survey spectra to identify a surprisingly large sample of
more massive very young galaxies (VYGs), defined to have formed at
least 50 per cent of their stellar mass within the last 1Gyr. Here,
we investigate in detail the properties of a subsample of 207 galaxies
that are VYGs according to all three of our spectral models. We
compare their properties with those of control sample galaxies (CSGs).
We find that VYGs tend to have higher surface brightness and to be
more compact, dusty, asymmetric, and clumpy than CSGs. Analysis of a
subsample with H I detections reveals that VYGs are more gas rich than
CSGs. VYGs tend to reside more in the inner parts of low-mass groups
and are twice as likely as CSGs to be interacting with a neighbour
galaxy. On the other hand, VYGs and CSGs have similar gas
metallicities and large-scale environments (relative to filaments and
voids). These results suggest that gas-rich interactions and mergers
are the main mechanisms responsible for the recent triggering of star
formation in low-redshift VYGs, except for the lowest mass VYGs, where
the starbursts would arise from a mixture of mergers and gas infall.
Description:
Properties of 207 very young galaxies and 1242 control sample
galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
info.dat 151 1449 Galaxy properties
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Byte-by-byte Description of file: info.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- objID SDSS objID
21- 39 I19 --- specObjID SDSS specObjID
41- 44 I4 --- Plate SDSS spectroscopic plate
46- 50 I5 --- MJD SDSS modified Julian date of
spectroscopic observation
52- 54 I3 --- Fiber SDSS spectroscopic fibre
56- 63 F8.4 deg RAdeg Right ascension (J2000)
65- 72 F8.4 deg DEdeg Declination (J2000)
74- 79 F6.4 --- z Galaxy spectroscopic redshift
81- 85 F5.2 [Msun] logM*Vaz15 Decimal logarithm of the galaxy stellar
mass (1)
87- 90 F4.2 --- C Galaxy concentration (2)
92- 96 F5.2 mag/arcsec2 mu50 Galaxy surface brightness (3)
98-102 F5.2 [-] logA1 ? Decimal logarithm of the asymmetry (4)
104-108 F5.2 [-] logS1 ? Decimal logarithm of the smoothness (4)
110-114 F5.2 [-] logOH ? Gas oxygen abundance log(O/H) + 12
116-120 F5.2 --- fgas ? Neutral gas mass fraction
122-127 F6.2 mag AvBalmer ? Internal extinction in the V band
estimated from the Balmer decrement
129-133 F5.2 mag Avcont Internal extinction in the V band
estimated from the SPS analysis
135-141 F7.2 kpc dist1kpc ? Distance, in kpc, to the closest
neighbour (5)
143-149 F7.2 --- dist1norm ? Distance, in units of theta50,
to the closest neighbour (5)
151 I1 --- Class [0/1]? Sample flag (6)
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Note (1): Obtained using the STARLIGHT code with Vazdekis et al.
(2015MNRAS.449.1177V 2015MNRAS.449.1177V) model.
Note (2): Concentration is defined as log(theta90/theta50), where theta90
and theta50 are the radii containing 90% and 50% of the Petrosian flux in
the r band (SDSS parameters petroR90r and petroR50r).
Note (3): Computed using Eq. 1 in Trevisan et al. (2021MNRAS.502.4815T 2021MNRAS.502.4815T).
Note (4): computed using the code Morfometryka.
Note (5): Closest neighbour galaxy brighter than mr + 1, where mr is the
r-band Petrosian magnitude of the target galaxy.
Note (6): Sample flag as follows:
0 = control sample galaxy
1 = very young galaxy
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Acknowledgements:
Marina Trevisan, marina.trevisan(at)ufrgs.br
(End) Marina Trevisan [UFRGS, Brazil], Patricia Vannier [CDS] 09-Sep-2021