J/ApJ/788/77 Milky Way L/T/M-dwarfs identified in BoRG survey (Holwerda+, 2014)
Milky Way red dwarfs in the BoRG survey: galactic scale-height and
the distribution of dwarf stars in WFC3 imaging.
Holwerda B.W., Trenti M., Clarkson W., Sahu K., Bradley L., Stiavelli M.,
Pirzkal N., De Marchi G., Andersen M., Bouwens R., Ryan R.
<Astrophys. J., 788, 77 (2014)>
=2014ApJ...788...77H 2014ApJ...788...77H (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, dwarfs ; Photometry, HST ;
Photometry, infrared ; Stars, distances
Keywords: Galaxy: disk - Galaxy: fundamental parameters - Galaxy: halo -
Galaxy: structure - stars: low-mass
Abstract:
We present a tally of Milky Way late-type dwarf stars in 68 Wide Field
Camera 3 (WFC3) pure-parallel fields (227 arcmin2) from the
Brightest of Reionizing Galaxies survey for high-redshift galaxies.
Using spectroscopically identified M-dwarfs in two public surveys, the
Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey and the Early
Release Science mosaics, we identify a morphological selection
criterion using the half-light radius (r50), a near-infrared J-H,
G-J color region where M-dwarfs are found, and a V-J relation with
M-dwarf subtype. We apply this morphological selection of stellar
objects, color-color selection of M-dwarfs, and optical-near-infrared
color subtyping to compile a catalog of 274 M-dwarfs belonging to the
disk of the Milky Way with a limiting magnitude of mF125W<24(AB).
Based on the M-dwarf statistics, we conclude that (1) the previously
identified north-south discrepancy in M-dwarf numbers persists in our
sample; there are more M-dwarfs in the northern fields on average than
in southern ones, (2) the Milky Way's single disk scale-height for
M-dwarfs is 0.3-4 kpc, depending on subtype, (3) the scale-height
depends on M-dwarf subtype with early types (M0-4) high scale-height
(z0=3-4 kpc) and later types M5 and above in the thin disk
(z0=0.3-0.5 kpc), (4) a second component is visible in the vertical
distribution, with a different, much higher scale-height in the
southern fields compared to the northern ones. We report the M-dwarf
component of the Sagittarius stream in one of our fields with 11
confirmed M-dwarfs, seven of which are at the stream's distance. In
addition to the M-dwarf catalog, we report the discovery of 1 T-dwarfs
and 30 L-dwarfs from their near-infrared colors. The dwarf
scale-height and the relative low incidence in our fields of L- and
T-dwarfs in these fields makes it unlikely that these stars will be
interlopers in great numbers in color-selected samples of
high-redshift galaxies. The relative ubiquity of M-dwarfs however will
make them ideal tracers of Galactic halo substructure with EUCLID and
reference stars for James Webb Space Telescope observations.
Description:
Our principal data set is the WFC3 data from the BoRG (HST GO/PAR-11700;
Trenti et al. 2011ApJ...727L..39T 2011ApJ...727L..39T; Bradley et al. 2012ApJ...760..108B 2012ApJ...760..108B)
survey to identify Milky Way dwarf stars from their morphology and
color. The BoRG observations are undithered HST/WFC3 conducted in
pure-parallel with the telescope pointing to a primary spectroscopic
target with the Cosmic Origin Spectrograph (COS; typically a high-z QSO
at high Galactic latitude). The limitations for such observations are
primarily that no dithering strategy can be used (final images are at
WFC3 native pixel scale) and total exposure times are dictated by the
primary program.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 67 24 The M-dwarfs Identified by PEARS in the CANDELS
Field
table5.dat 67 22 The M-dwarfs Identified by PEARS in the ERS Mosaic
table14.dat 137 30 The 30 L-dwarfs Identified in BoRG
table15.dat 137 1 The 1 T-dwarfs Identified in BoRG
table16.dat 137 274 The 274 M-dwarfs identified in BoRG
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
J/A+A/441/653 : 32 DENIS nearby red dwarfs (Crifo+, 2005)
Byte-by-byte Description of file: table4.dat table5.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID Identification number, NNNNNN,
[PBM2009] sNNNNNN in Simbad
8- 10 F3.1 --- SpType Sub M spectral type
12- 20 F9.6 deg RAdeg Rigth ascension (J2000)
22- 31 F10.6 deg DEdeg Declination (J2000)
33- 37 F5.2 mag F435Wmag F435W magnitude (1)
39- 43 F5.2 mag F606Wmag F606W magnitude (1)
45- 49 F5.2 mag F775Wmag F775W magnitude (1)
51- 55 F5.2 mag F850Wmag F850W magnitude (1)
57- 61 F5.2 mag F125Wmag F125W magnitude (2)
63- 67 F5.2 mag F160Wmag F160W magnitude (2)
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Note (1): Optical magnitudes are from Pirzkal et al. (2009, Cat. J/ApJ/695/1591)
Note (2): F125W and F160W magnitudes from our sextractor catalog of the
CANDELS field (table 4) or ERS mosaic (table 5).
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Byte-by-byte Description of file: table14.dat table15.dat table16.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [borg_]
6- 21 A16 --- borg Source identifier (borg_HHMM+DDMM.NNNN.N)
23- 32 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
34- 43 F10.6 deg DEdeg Declination in decimal degrees (J2000)
45- 54 F10.6 deg GLON Galactic longitude
56- 65 F10.6 deg GLAT Galactic latitude
67- 70 F4.1 mag F098Mmag HST/WFC3 F098M filter magnitude
72- 74 F3.1 mag e_F098Mmag Uncertainty in F098Mmag
76- 79 F4.1 mag F125Wmag HST/WFC3 F125W filter magnitude
81- 83 F3.1 mag e_F125Wmag Uncertainty in F125Wmag
85- 88 F4.1 mag F160Wmag HST/WFC3 F160W filter magnitude
90- 92 F3.1 mag e_F160Wmag Uncertainty in F160Wmag
94- 97 F4.1 mag F606Wmag HST/WFC3 F606W filter magnitude
99-102 F4.1 mag e_F606Wmag Uncertainty in F606Wmag
104-107 F4.1 --- Mtype ? M-dwarf type; see Equ. 4.
109-111 F3.1 --- e_Mtype ? Uncertainty in Mtype
113-117 F5.2 mag DM ? Distance modulus
119-123 F5.2 kpc Dist ? Distance
125-130 F6.2 kpc Z ? Milky Way scale height
132-137 F6.2 kpc Rad []? Galactic radius
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 07-Jul-2017