J/A+A/619/A163 CIG 96 deep optical and HI images (Ramirez-Moreta+, 2018)
Unveiling the environment and faint features of the isolated galaxy
CIG 96 with deep optical and HI observations.
Ramirez-Moreta P., Verdes-Montenegro L., Blasco-Herrera J., Leon S.,
Venhola A., Yun M., Peris V., Peletier R., Verdoes Kleijn G.,
Unda-Sanzana E., Espada D., Bosma A., Athanassoula E., Argudo-Fernandez M.,
Sabater J., Munoz-Mateos J.C., Jones M.G., Huchtmeier W., Ruiz J.E.,
Iglesias-Paramo J., Fernandez-Lorenzo M., Beckman J., Sanchez-Exposito S.,
Garrido J.
<Astron. Astrophys. 619, A163 (2018)>
=2018A&A...619A.163R 2018A&A...619A.163R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; H I data ; Photometry ; Optical
Keywords: galaxies: individual: NGC 864 - galaxies: spiral -
galaxies: structure - galaxies: evolution -
galaxies: kinematics and dynamics - galaxies: photometry -
radio lines: galaxies
Abstract:
Asymmetries in atomic hydrogen (HI) in galaxies are often caused by
the interaction with close companions, making isolated galaxies an
ideal framework to study secular evolution. The AMIGA project has
demonstrated that isolated galaxies show the lowest level of asymmetry
in their HI integrated profiles compared to even field galaxies, yet
some present significant asymmetries. CIG 96 (NGC 864) is a
representative case reaching a 16% level.
Our aim is to investigate the HI asymmetries of the spiral galaxy
CIG 96 and what processes have triggered the star-forming regions
observed in the XUV pseudo-ring.
We performed deep optical observations at CAHA1.23m, CAHA2.2m and VST
(OmegaCAM wide-field camera) telescopes. We reach surface brightness
(SB) limits of µCAHA2.2m=27.5mag/arcsec2 (Cousins R) and
µVST=28.7mag/arcsec2 (SDSS r) that show the XUV pseudo-ring of
the galaxy in detail. Additionally, a wavelet filtering of the HI data
cube from our deep observations with VLA/EVLA telescope allowed us to
reach a column density of NHI=8.9x1018cm-2 (5σ) (28"x28"
beam), lower than in any isolated galaxy.
We confirm that the HI of CIG 96 extends farther than 4xr25 in all
directions. Furthermore, we detect for the first time two gaseous
structures (∼106M☉) in the outskirts. The SDSS g-r colour
index image from CAHA1.23m shows extremely blue colours in certain
regions of the pseudo-ring where NHI>8.5x1020cm-2, whereas the
rest show red colours. Galactic cirrus contaminate the field, setting
an unavoidable detection limit at 28.5mag/arcsec2 (SDSS r).
At the current SB and NHI levels, we detect no stellar link within
1°x1° or gaseous link within 40'x40' between CIG 96 and any
companion. The isolation criteria rule out interactions with other
similar-sized galaxies for at least 2.7Gyr. Using existing stellar
evolution models, the age of the pseudo-ring is estimated at 1Gyr or
older. Undetected previously accreted companions and cold gas
accretion remain as the main hypothesis to explain the optical
pseudo-ring and HI features of CIG 96.
Description:
In two different epochs, 21cm line observations of CIG 96 were made
using the NRAO Karl G. Jansky Very Large Array (hereafter VLA or EVLA)
observatory. First, two VLA projects AV0276 and AV0282 were performed
in July 2004 and July 2005, respectively. We obtained 3 hours in
D-configuration (26 antennas used) and 7 hours in C-configuration (27
antennas used), respectively. Both observing projects had the same set
up: 2 IF correlator mode, a bandwidth of 3.125MHz per IF and a
frequency resolution of 48.8kHz that corresponds to a velocity
resolution of 10.4km/s. Second, the Extended-VLA (EVLA) project
13A-341, fully dedicated to observing CIG 96, was executed during 2013
as follows: 3 hours in March, in Dconfiguration; 3 hours in May in the
hybrid DnC-configuration and 10 hours in July, in C-configuration. In
all cases, 27 antennas were used.
The set-up of these observations consisted of single IF correlator
mode, a bandwidth of 2MHz and a frequency resolution of 16kHz,
equivalent to a velocity resolution of 3.3km/s that was smoothed
to 10km/s for the calculations.
CIG 96 was first observed in the second half of the night of September
11, 2012, with the CAFOS instrument at CAHA2.2m telescope. The CAFOS
SITe1d detector has 2048x2048 pixels with a pixel size of 24um
(spatial scale of 0.53"/pix), providing an effective circular field of
view of ∼12' in diameter.
CIG 96 was observed for a second time on the night of December 8, 2012
with the DLR-MKIII instrument at the CAHA 1.23m telescope. The camera
is equipped with an e2v CCD231-84-NIMO-BI-DD sensor (4kx4k pixels,
15um/pix).
In order to study the larger-scale structure surrounding CIG 96, we
also observed the galaxy with OmegaCAM at the VST (runID:
098.B-0775(A)). This instrument has a field of view of 1 square degree
sampled with a 32-CCD, 16kx16k detector mosaic at 0.21"/pix.
In order to inspect the cirrus around CIG 96 (see Sect. 4.6), we used
images from the HFI camera of the Planck satellite at 857GHz/350um
band (Planck Collaboration et al., 2014A&A...571A...1P 2014A&A...571A...1P). Also, we have
used a WISE band 3 image (12um) since this band that traces hot dust
and shows good correlation with the cirrus emission (Miville-Deschenes
et al., 2016A&A...593A...4M 2016A&A...593A...4M).
Objects:
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RA (2000) DE Designation(s)
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02 15 27.64 +06 00 09.4 NGC 864 = K73 96
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 245 12 List of fits files
fits/* . 12 Individual fits files
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 F4.2 arcsec/pix scale ? Scale of the image
25- 28 I4 --- Nx Number of pixels along X-axis
30- 33 I4 --- Ny Number of pixels along Y-axis
35- 36 I2 --- Nz ? Number of slices for the datacube
38- 56 A19 "datime" Obs.date Observation date (YYYY-MM-DDThh:mm:ss)
58- 63 I6 Kibyte size Size of FITS file
65-127 A63 --- FileName Name of FITS file, in subdirectory fits
129-245 A117 --- Title Title of the FITS file
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Acknowledgements:
Pablo Ramirez-Moreta, prm(at)iaa.es
(End) Patricia Vannier [CDS] 27-Sep-2018