J/ApJ/751/46 Spectroscopic observations in VV124 (UGC 4879) (Kirby+, 2012)
The dynamics and metallicity distribution of the distant dwarf galaxy VV124.
Kirby E.N., Cohen J.G., Bellazzini M.
<Astrophys. J., 751, 46 (2012)>
=2012ApJ...751...46K 2012ApJ...751...46K
ADC_Keywords: Galaxies, nearby ; Radial velocities ; Abundances, [Fe/H] ;
Equivalent widths ; Photometry, ugriz
Keywords: galaxies: abundances - galaxies: dwarf - Local Group -
galaxies: individual: VV124 - galaxies: kinematics and dynamics
Abstract:
VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal
(dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous
low-resolution spectroscopy yielded inconsistent radial velocities for
different components of the galaxy, and photometry hinted at the
presence of a stellar disk. In order to quantify the stellar dynamics,
we observed individual red giants in VV124 with the Keck/Deep
Extragalactic Imaging Multi-Object Spectrograph (DEIMOS). We validated
members based on their positions in the color-magnitude diagram,
radial velocities, and spectral features. Our sample contains 67
members. The average radial velocity is <vr≥-29.1±1.3km/s in
agreement with the previous radio measurements of H I gas. The
velocity distribution is Gaussian, indicating that VV124 is supported
primarily by velocity dispersion inside a radius of 1.5 kpc. Outside
that radius, our measurements provide only an upper limit of 8.6km/s
on any rotation in the photometric disk-like feature. The velocity
dispersion is σv=9.4±1.0km/s, from which we inferred a mass
of M1/2=(2.1 ±0.2)x107M☉ and a mass-to-light ratio of
(M/LV)1/2=5.2±1.1M☉/L☉, both measured within the
half-light radius. Thus, VV124 contains dark matter. We also measured
the metallicity distribution from neutral iron lines. The average
metallicity, <[Fe/H]≥-1.14±0.06, is consistent with the
mass-metallicity relation defined by dSph galaxies. The dynamics and
metallicity distribution of VV124 appear similar to dSphs of similar
stellar mass.
Description:
Targets were selected from B11a's photometric catalog (Bellazzini et
al., 2011A&A...527A..58B 2011A&A...527A..58B) in which deep g and r photometry was
acquired on the night of December 2, 2008, at the Large Binocular
Telescope (LBT), using the blue channel of the Large Binocular Camera.
We observed two slitmasks with Keck/DEIMOS, called vv124a and vv124b,
on 2011 January 30 (UT). We used the 1200 lines/mm grating centered at
7800Å. This grating, combined with the slit widths of 0.7", yielded
a line spread profile with an FWHM of 1.2Å. The resolving power is
about R∼7000 near the CaII triplet (CaT) at 8500Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 111 131 Target list (from erratum in 2013,ApJ,768,96)
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See also:
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/A+A/533/A37 : VI HST photometry of VV124 = UGC4879 (Bellazzini+, 2011)
J/ApJS/191/352 : Milky Way dwarf satellites abundances (Kirby+, 2010)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)
J/ApJ/659/162 : CAS parameters of 199 nearby galaxies (Taylor-Mager+, 2007)
J/MNRAS/380/281 : Faint galactic satellites spectro. survey (Martin+, 2007)
J/PASP/117/227 : Properties of 101 galaxies from the NFGS (Kewley+, 2005)
J/ApJ/630/784 : UBVR observations of nearby galaxies (Taylor+, 2005)
J/A+A/414/23 : CCD Hα and R photometry of 334 galaxies (James+, 2004)
J/ApJS/149/327 : JKs photometry of local universe galaxies (Grauer+, 2003)
J/ApJ/543/178 : Nearby Optical Galaxy (NOG) sample (Giuricin+, 2000)
J/ApJS/126/331 : Spectrophotometry of nearby field galaxies (Jansen+ 2000)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [1167/17428] Object identification from
Bellazzini et al. 2011A&A...527A..58B 2011A&A...527A..58B
7- 8 I2 h RAh Hour of Right Ascension (J2000)
10- 11 I2 min RAm Minute of Right Ascension (J2000)
13- 16 F4.1 s RAs Second of Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000)
30- 35 F6.3 mag gmag [19/26] LBT g band magnitude
37- 41 F5.3 mag e_gmag [0.003/0.06] Uncertainty in gmag
43- 48 F6.3 mag rmag [18/24] LBT r band magnitude
50- 54 F5.3 mag e_rmag [0.004/0.06] Uncertainty in rmag
56 I1 --- N [1/2] Number of DEIMOS masks on which the object
was observed
58- 62 F5.1 0.1nm-1 SNR [2/134] Signal-to-noise ratio per Angstrom (Å)
64- 69 F6.1 km/s HRV [-194/52]? Heliocentric radial velocity
71- 74 F4.1 km/s e_HRV [2/14]? Uncertainty in HRV
76- 79 F4.2 0.1nm EWNa [0.2/4.2]? NaI8190 doublet equivalent width (Å)
in Angstroms
81- 84 F4.2 0.1nm e_EWNa [0.02/0.4]? Uncertainty in EWNa (Å)
86- 90 F5.2 [Sun] [Fe/H] [-3/-0.05]? Logarithmic iron abundance relative
to the Sun
92- 95 F4.2 [Sun] e_[Fe/H] [0.2/0.5]? Uncertainty in [Fe/H]
97 A1 --- Mm [N/Y] Object considered to be member of VV124?
99-111 A13 --- n_Mm Reason(s) object considered to be non-member (1)
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Note (1): the symbols used are:
v_r = inappropriate radial velocity.
Na = spectrum shows strong NaIλ8190 doublet
G = spectrum shows emission lines or redshifted Ca H and K lines,
indicating that the object is a galaxy.
Bright = target is brighter than the tip of the red giant branch (TRGB)
Bad = spectral quality was insufficient for radial velocity
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Nomenclature note:
In table 2, stars are <[KCB2012] NNNNN> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Dec-2013