J/MNRAS/501/281 Ultracool dwarfs in ALHAMBRA and COSMOS (Solano+, 2021)
Ultracool dwarfs in deep extragalactic surveys using the virtual observatory:
ALHAMBRA and COSMOS.
Solano E., Galvez-Ortiz M.C., Martin E.L., Gomez Munoz I.M., Rodrigo C.,
Burgasser A.J., Lodieu N., Bejar V.J.S., Huelamo N., Morales-Calderon M.,
Bouy H.
<Mon. Not. R. Astron. Soc., 501, 281-290 (2021)>
=2021MNRAS.501..281S 2021MNRAS.501..281S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, brown dwarf ; Parallaxes, trigonometric ; Proper motions ;
Spectral types ; Optical
Keywords: surveys - virtual observatory tools - brown dwarfs - stars: low-mass
Abstract:
Ultracool dwarfs (UCDs) encompass a wide variety of compact
stellar-like objects with spectra classified as late-M, L, T, and Y.
Most of them have been discovered using wide-field imaging surveys.
The Virtual Observatory (VO) has proven to be of great utility to
efficiently exploit these astronomical resources. We aim to validate a
VO methodology designed to discover and characterize UCDs in deep
extragalactic surveys like Advance Large Homogeneous Area Medium-Band
Redshift Astronomical (ALHAMBRA) and Cosmological Evolution Survey
(COSMOS). Three complimentary searches based on parallaxes, proper
motions and colours, respectively, were carried out. A total of 897
candidate UCDs were found, with only 16 previously reported in SIMBAD.
Most of the new UCDs reported here are likely late-M and L dwarfs
because of the limitations imposed by the utilization of optical (Gaia
DR2 and r-band) data. We complement ALHAMBRA and COSMOS photometry
with other catalogues in the optical and infrared using VOSA, a VO
tool that estimates effective temperatures from the spectral energy
distribution fitting to collections of theoretical models. The
agreement between the number of UCDs found in the COSMOS field and
theoretical estimations together with the low false-negative rate
(known UCDs not discovered in our search) validates the methodology
proposed in this work, which will be used in the forthcoming wide and
deep surveys provided by the Euclid space mission. Simulations of
Euclid number counts for UCDs detectable in different photometric
passbands are presented for a wide survey area of 15000deg2, and the
limitations of applicability of Euclid data to detect UCDs using the
methods employed in this paper are discussed.
Description:
Using a VO methodology, we have built a catalogue of 897 candidate
ultracool dwarfs (UCDs) found in the ALHAMBRA and COSMOS extragalactic
surveys. In total, 16 of them were already known in SIMBAD. Our
primary goal in this paper was not to carry out a detailed analysis on
the properties of the found candidates but to define and assess a
search methodology to be used for deeper and larger surveys like
Euclid, whose excellent sensitivity makes it an ideal resource for the
discovery of new UCDs, including BDs with very low effective
temperatures.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 261 897 The SVO archive of ultracool dwarfs identified
in ALHAMBRA and COSMOS
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 18 F18.14 deg RAdeg Right ascension (J2000)
20- 29 F10.7 deg DEdeg Declination (J2000)
31- 45 F15.8 arcsec Dist Distance from ConeSearch center position
47- 54 A8 --- Survey Survey (ALHAMBRA or COSMOS)
56- 66 I11 --- ID Source identifier in ALHAMBRA or COSMOS
68- 86 I19 --- GaiaDR2 ? Gaia DR2 source identifier
88- 94 F7.4 mas plx ? Gaia DR2 parallax
96- 101 F6.4 mas e_plx ? Error on plx
103- 109 F7.3 mas/yr pmRA ? Gaia DR2 proper motion in right
ascension
111- 115 F5.3 mas/yr e_pmRA ? Error on pmRA
117- 123 F7.3 mas/yr pmDE ? Gaia DR2 proper motion in declination
125- 129 F5.3 mas/yr e_pmDE ? Error on pmDE
131- 139 F9.6 mag Gmag ? Gaia DR2 G-band magnitude
141- 149 F9.6 mag RPmag ? Gaia DR2 RP-band magnitude
151- 154 A4 --- Method Method used to identify the source (1)
156- 159 I4 K Teff Effective temperature estimated using VOSA
161- 163 A3 --- SpTypeSim Spectral type from Simbad
165- 169 A5 --- SpTypeSDSS Spectral type from SDSS
171- 261 A91 --- Spectrum Link to the SDSS DR16 spectrum
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Note (1): Method as follows:
HRD = Hertzsprung-Russell diagram
RPM = Reduced proper motion
PHOT = photometric colour
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 16-Oct-2023