J/A+A/612/A26 Deep HI observations of Leo T with WSRT (Adams+, 2018)
Deep neutral hydrogen observations of Leo T with the Westerbork Synthesis
Radio Telescope.
Adams E.A.K, Oosterloo T.A
<Astron. Astrophys. 612, A26 (2018)>
=2018A&A...612A..26A 2018A&A...612A..26A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Photometry, CCD ;
H I data
Keywords: galaxies: ISM - galaxies: dwarf - Local Group -
radio lines: galaxies - galaxies: individual: Leo T -
galaxies: star formation
Abstract:
Leo T is the lowest mass gas-rich galaxy currently known and studies
of its gas content help us understand how such marginal galaxies
survive and form stars. We present deep neutral hydrogen (HI)
observations from the Westerbork Synthesis Radio Telescope in order to
understand its HI distribution and potential for star formation.
We find a larger HI line flux than the previously accepted value,
resulting in a 50% larger HI mass of 4.1x105M☉.
The additional HI flux is from low surface brightness emission that
was previously missed; with careful masking this emission can be
recovered even in shallower data.We perform a Gaussian spectral
decomposition to find a cool neutral medium component (CNM) with a
mass of 3.7x104M☉, or almost 10% of the total HI mass.
Leo T has no HI emission extending from the main HI body, but there is
evidence of interaction with the Milky Way circumgalactic medium in
both a potential truncation of the HI body and the offset of the peak
HI distribution from the optical center. The CNM component of Leo T is
large when compared to other dwarf galaxies, even though Leo T is not
currently forming stars and has a lower star formation efficiency than
other gas-rich dwarf galaxies.
However, the HI column density associated with the CNM component in
Leo T is low. One possible explanation is the large CNM component is
not related to star formation potential but rather a recent, transient
phenomenon related to the interaction of Leo T with the Milky Way
circumgalactic medium.
Description:
The final cleaned data cube for ten 12-hr WSRT tracks combined is
presented, along with a total intensity, primary-beam corrected HI map
(in units of 1020atoms/cm2) and moment one (velocity field) and
moment two (velocity dispersion) maps, both in units of km/s.
Objects:
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RA (2000) DE Designation(s)
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09 34 53.4 +17 03 05 Leo T = NAME Leo T dSph
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 173 4 List of fits files
fits/* . 4 Individual fits images and data cube
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See also:
J/ApJ/756/108 : Variable stars in Leo T HST VI photometry (Clementini+, 2017)
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 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 32 I3 --- Nz ? Number of slices
34- 54 A21 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.s)
56- 63 F8.1 m/s HVel Heliocentric velocity, or lower value of the
heliocentric velocity for the datacube
65- 70 I6 m/s BHVel ? Upper value of the heliocentric velocity
interval for the datacube
72- 78 F7.3 m/s dHVel ? Heliocentric velocity resolution for the
datacube
80- 85 I6 Kibyte size Size of FITS file
87-100 A14 --- FileName Name of FITS file, in subdirectory fits
102-173 A72 --- Title Title of the FITS file
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Acknowledgements:
Betsey Adams, adams(at)astron.nl
(End) Patricia Vannier [CDS] 18-Dec-2017