J/A+A/643/A176 Halpha+[NII] imaging of Dorado galaxies (Rampazzo+, 2020)
Dorado and its member galaxies. Halpha imaging of the group backbone.
Rampazzo R., Ciroi S., Mazzei P., Di Mille F., Congiu E., Cattapan A.,
Bianchi L., Iodice E., Marino A., Plana H., Postma J., Spavone M.
<Astron. Astrophys. 643, A176 (2020)>
=2020A&A...643A.176R 2020A&A...643A.176R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies ; Interstellar medium
Keywords: galaxies: elliptical and lenticular, cD - galaxies: spiral -
galaxies: ISM - galaxies: interactions - galaxies: evolution
Abstract:
Dorado is a nearby, rich and clumpy galaxy group that extends for
several degrees in the Southern Hemisphere. Although several studies
have been dedicated to define its members, their kinematics, hot and
cold gas content, in particular HI, their present star formation
activity is yet unknown.
For the first time, we map the Hα distribution as a possible
indicator of star formation activity of Dorado members a large
fraction of which show interaction and merging signatures, regardless
of their morphological type.
With the 2.5m du Pont and the 1m Swope telescopes we obtained
narrow-band, calibrated images of 14 galaxies, forming the backbone of
the group, mapping Hα+[NII] down to few
10-17erg/cm2/s/arcsec2. We estimated the galaxy star formation
rate from the Hα fluxes, corrected for Galaxy foreground
extinction and [NII] contamination.
Hα+[NII] emission has been detected in all galaxies. HII regions
clearly emerge in late-type galaxies, while in early-type galaxies the
Hα+[NII] emission is dominated by [NII], especially in the
central regions. However, HII complexes are revealed in four early-type
galaxies. Even in the compact group SGC 0414-5559, in the projected
centre of Dorado, HII regions are found both through out the late-type
galaxies and in the very outskirts of early-type members. Considering
the Dorado group as a whole, we notice that the Hα+[NII]
equivalent width, a measure of the specific star formation, increases
with the morphological type, from early to late-type members, although
it remains lower that what observed in similar surveys of spiral
galaxies. The star formation rate of the spiral members is in the
range of what observed in similar galaxies surveys (James et al.,
2004A&A...414...23J 2004A&A...414...23J, Cat. J/A+A/414/23). However, in three spiral
NGC 1536, PGC 75125 and IC 2058 the star formation rate is well below
the median for their morphological classes. The star formation rate of
some early-type members tends, at odds, to be higher than the average
derived from Hα+[NII] surveys of this morphological family.
We detected in Hα+[NII] all the early type galaxies observed and
half of them show HII regions in well shaped rings as well as in their
outskirts. These findings suggest that ETGs in this group are not dead
galaxies: their star formation has not shutdown yet. Mechanisms such
as gas stripping and gas accretion, through galaxy-galaxy interaction,
seem relevant in modifying star formation in this evolutionary phase
of Dorado.
Description:
Hα+[NII] images have been obtained using the direct CCD Camera at
the du Pont 2.5m and at Swope 1m telescopes at Las Campanas Observatory
(LCO, Chile). Observations cover the period between November 30th and
December 7th, 2018.
The .fits files are single pointings with du Pont and Swope telescopes.
the pointings are indicated with letter a, b, c etc. after the
galaxyID the file convention name is galaxyID_HAC.fit for continuum
images and galaxyID_HA.fits for images in the Halpha + [NII] filter.
e.g IC2038_HA.fits Ha+[NII] image of IC 2038, NGC1543a_HAC.fits
continuum image of NGC1543 pointing "a". Multiple images were later
registered to form a mosaic.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
04 17 54.37 -55 55 57.7 IC2058 = IC 2058
04 09 51.84 -56 07 06.4 NGC1533 = NGC 1533
04 10 59.84 -56 28 49.6 NGC1536 = NGC 1536
04 12 43.17 -57 44 16.3 NGC1543 = NGC 1543
04 14 36.54 -56 03 38.9 NGC1546 = NGC 1546
04 15 45.22 -55 35 32.5 NGC1549 = NGC 1549
04 16 10.47 -55 46 48.1 NGC1553 = NGC 1553
04 20 00.40 -54 56 16.6 NGC1566 = NGC 1566
04 24 44.92 -54 56 31.3 NGC1581 = NGC 1581
04 27 38.11 -55 01 39.8 NGC1596 = NGC 1596
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 125 42 List of fits images
fits/* . 42 Individual fits images
--------------------------------------------------------------------------------
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- 24 F5.3 arcsec/pix scale Scale of the image
26- 29 I4 --- Nx Number of pixels along X-axis
31- 34 I4 --- Ny Number of pixels along Y-axis
36- 45 A10 "date" Obs.date Observation date
47- 51 I5 Kibyte size Size of FITS file
53- 69 A17 --- FileName Name of FITS file, in subdirectory fits
71-125 A55 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Roberto Rampazzo, roberto.rampazzo(at)inaf.it
(End) Patricia Vannier [CDS] 02-Oct-2020