J/MNRAS/491/3496 Andromeda XIX member stars (Collins+, 2020)
A detailed study of Andromeda XIX, an extreme local analogue of
ultradiffuse galaxies.
Collins M.L.M., Tollerud E.J., Rich R.M., Ibata R.A., Martin N.F.,
Chapman S.C., Gilbert K.M., Preston J.
<Mon. Not. R. Astron. Soc., 491, 3496-3514 (2020)>
=2020MNRAS.491.3496C 2020MNRAS.491.3496C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry ; Optical
Keywords: stars: kinematics and dynamics - galaxies: dwarf
Abstract:
With a central surface brightness of µ0=29.3mag/arcsec2, and
half-light radius of rhalf=3.1+0.9-1.1kpc, Andromeda XIX (And
XIX) is an extremely diffuse satellite of Andromeda. We present
spectra for ∼100 red giant branch stars in this galaxy, plus 16
stars in a nearby stellar stream. With this exquisite data set, we
re-derive the properties of And XIX, measuring a systemic velocity of
<vr≥-109.0±1.6km/s and a velocity dispersion of
σvr=7.8+1.7-1.5km/s (higher than derived in our previous
work). We marginally detect a velocity gradient along the major axis
of dv/dX=-2.1±1.8km/s/kpc. We find its mass-to-light ratio is higher
than galaxies of comparable stellar mass
([M/L]half=278+146-198M☉/L☉), but its dynamics place
it in a halo with a similar total mass to these galaxies. This could
suggest that And XIX is a 'puffed up' dwarf galaxy, whose properties
have been altered by tidal processes, similar to its Milky Way
counterpart, Antlia II. For the nearby stream, we measure
vr=-279.2±3.7km/s, and σrv=13.8+3.5-2.6km/s. We
measure its metallicity, and find it to be more metal rich than And
XIX, implying that the two features are unrelated. Finally, And XIX's
dynamical and structural properties imply it is a local analogue to
ultradiffuse galaxies (UDGs). Its complex dynamics suggest that the
masses of distant UDGs measured from velocity dispersions alone should
be carefully interpreted.
Description:
We conducted deep imaging of And XIX using Suprime-cam on the Subaru
telescope on 2008 August 24 in photometric conditions, with
sub-arcsecond seeing (average of ∼0.7arcsec). Suprime-cam has a
field of view of 27x34arcmin, allowing coverage of ∼1 half-light
radii of And XIX in this single pointing. We used the wide V- (JC) and
i-band (AB) filters, integrating for 3x400 and 9x220s in each band,
respectively.
Objects:
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RA (2000) DE Designation(s)
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00 19 32.10 +35 02 37.1 And XIX = LEDA 5056919
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 66 545 Properties of all member stars for And XIX and
observed stars
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000)
12- 20 F9.6 deg DEdeg Declination (J2000)
22- 26 F5.2 mag Vmag V magnitude
28- 32 F5.2 mag imag i magnitude (AB)
34- 39 F6.1 km/s HV Heliocentric velocity
41- 44 F4.1 km/s e_HV rms uncertainty on HV
46- 51 F6.3 --- S/N Signal-to-noise ratio (in 1/Å unit)
53- 56 F4.1 [-] [Fe/H] ?=9.9 Metallicity (1)
58- 60 F3.1 [-] e_[Fe/H] ?=9.9 rms uncertainty on [Fe/H] (1)
62- 66 F5.3 --- Pmemb [0/1] Membership probability
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Note (1): Values of [Fe/H]=9.9 indicate a failure to determine a metallicity
for that object.
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Acknowledgements:
Nicolas Martin, nicolas.martin(at)astro.unistra.fr
(End) Patricia Vannier [CDS] 27-May-2021