J/A+A/664/A192 FUV imaging of Dorado galaxies (Rampazzo+, 2022)
Dorado and its member galaxies.
III. Mapping star formation with FUV imaging from UVIT.
Rampazzo R., Mazzei P., Marino A., Bianchi L., Postma J., Ragusa R.,
Spavone M., Iodice E., Ciroi S., Held E.V.
<Astron. Astrophys. 664, A192 (2022)>
=2022A&A...664A.192R 2022A&A...664A.192R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies ; Ultraviolet
Keywords: ultraviolet: galaxies - galaxies: elliptical and lenticular, cD -
galaxies: spiral - galaxies: interaction - galaxies: evolution
Abstract:
We are investigating the star formation in galaxies of the actively
evolving Dorado group where, for a large fraction of both early- and
late-type galaxies, signatures of interactions and merging events are
revealed by optical and radio observations.
Our previous Hα+[NII] study, probing ∼10Myr timescales,
suggested that star formation is still ongoing in early-type galaxies.
In this work, we use far-UV (FUV) imaging to map recent star formation
on longer timescales, on the order of 100Myr.
We used the Ultraviolet Imaging Telescope UVIT on board Astrosat to
image the galaxies of the Dorado backbone previously observed in
Hα+[NII], with the far-UV filter FUV.CaF2 (1300-1800Å). The
sample included NGC 1536, NGC 1546, NGC 1549, [CMI2001]4136-01,
NGC 1553, IC 2058, PGC 75125, NGC 1566, NGC 1596, and NGC 1602; for
the two latter galaxies, the UVIT data provided the first view in
far-UV. For the others, previously observed by GALEX, the UVIT data
afford a ∼5x improvement in spatial resolution.
FUV.CaF2 emission is revealed in all the Dorado galaxies observed,
tracing young stellar populations in ring structures and showing tidal
distortions. The Sersic index, derived by fitting the luminosity
profiles, is always n<3, suggesting that the FUV.CaF2 emission
originates from a disk also in early-type galaxies. The star formation
rate (SFR) ranges from 0.004±0.001M☉/yr for [CMI2001] 4136-01
to 2.455±0.027M☉/yr for NGC 1566. Most of the recent star
formation is found at the periphery of the Dorado group, where most of
late-type galaxies are located. For these galaxies, the ratio
SFRHα/SFRFUV.CaF2 is close to 1, except for the edge-on IC 2058,
similar to previously reported relations for local volume samples. For
early-type galaxies, however, SFRHα is about 15 times higher
than SFRFUV. Dorado's early-type galaxies define a separate locus in
SFRFUV, SFRHα space with respect to the late-type galaxies,
which is well represented by the relation
log(SFRFUV.CaF2)=0.70xlog(SFRHα)-1.26.
The disk structure of the FUV.CaF2 emitting populations discovered in
all the early-types galaxies implies dissipative processes and wet
merging events. The systematic discrepancy between SFRs derived from
Hα and FUV fluxes suggests that rejuvenation episodes in
early-type galaxies cannot sustain constant star formation over
∼100Myr timescales.
Description:
Astrosat is an X-ray-UV observatory launched by the Indian Space
Research Organization on September 28, 2015. The Ultra-Violet Imaging
Telescope facility UVIT is composed of two Ritchey-Chretien
telescopes, each with a 37.5 cm aperture and a circular field of view
with a diameter of 28'. Originally, one telescope observed FUV
wavelengths (1300-1800Å) and the other both NUV (2000-3000Å)
and optical band (VIS) wavelengths (3200-5500Å), by means of a
beam-splitter directing NUV and VIS to individual cameras.
Images reconstructed from the photon-counting data with 0416
sub-sampling were rebinned for our analysis, to enhance the
signal-to-noise ratio (S/N) to 1664px-1. The nominal zero point
magnitude of the FUV.CaF2 filter is 18.08mag (Tandon et al.,
2017AJ....154..128T 2017AJ....154..128T).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 142 7 List of fits images
fits/* . 7 Individual fits images
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See also:
J/AJ/121/148 : Photometry of Dorado Group Dwarf Galaxies (Carrasco+, 2001)
J/A+A/643/A176 : Halpha+[NII] imaging of Dorado galaxies (Rampazzo+, 2020)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension of center (J2000)
4- 5 I2 min RAm Right ascension of center (J2000)
7- 11 F5.2 s RAs Right ascension of center (J2000)
13 A1 --- DE- Declination sign of center (J2000)
14- 15 I2 deg DEd Declination of center (J2000)
17- 18 I2 arcmin DEm Declination of center (J2000)
20- 23 F4.1 arcsec DEs Declination of center (J2000)
25- 28 I4 --- Nx Number of pixels along X-axis
30- 33 I4 --- Ny Number of pixels along Y-axis
35- 44 A10 "datime" Obs.date Observation date
46- 51 I6 Kibyte size Size of FITS file
53- 64 A12 --- FileName Name of FITS file, in subdirectory fits
66-142 A77 --- Title Title of the FITS file
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Acknowledgements:
Roberto Rampazzo, roberto.rampazzo(at)inaf.it
References:
Rampazzo et al., Paper I 2020A&A...643A.176R 2020A&A...643A.176R, Cat. J/A+A/643/A176
Rampazzo et al., Paper II 2021JApA...42...31R 2021JApA...42...31R
(End) Patricia Vannier [CDS] 03-Jun-2022