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Title: ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOOeTES I DWARF SPHEROIDAL GALAXY

Abstract

We develop, implement, and characterize an enhanced data reduction approach which delivers precise, accurate, radial velocities from moderate resolution spectroscopy with the fiber-fed VLT/FLAMES+GIRAFFE facility. This facility, with appropriate care, delivers radial velocities adequate to resolve the intrinsic velocity dispersions of the very faint dwarf spheroidal (dSph) galaxies. Importantly, repeated measurements let us reliably calibrate our individual velocity errors (0.2 kms{sup -1} {<=} {delta}{sub V} {<=} 5 km s{sup -1}) and directly detect stars with variable radial velocities. We show, by application to the Booetes I dSph, that the intrinsic velocity dispersion of this system is significantly below 6.5 km s{sup -1} reported by previous studies. Our data favor a two-population model of Booetes I, consisting of a majority 'cold' stellar component, with velocity dispersion 2.4{sup +0.9}{sub -0.5} km s{sup -1}, and a minority 'hot' stellar component, with velocity dispersion {approx}9 km s{sup -1}, although we cannot completely rule out a single component distribution with velocity dispersion 4.6{sup 0.8}{sub -0.6} km s{sup -1}. We speculate that this complex velocity distribution actually reflects the distribution of velocity anisotropy in Booetes I, which is a measure of its formation processes.

Authors:
; ; ; ; ; ;  [1]; ; ; ;  [2];  [3];  [4];  [5];  [6]
  1. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  2. Departamento de Astronomia, Universidad de Concepcion (Chile)
  3. Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia)
  4. Department of Physics and Astronomy, University of Leicester, Leics (United Kingdom)
  5. Department of Physics and Astronomy, The Johns Hopkins University, 3900 N. Charles Street, Baltimore, MD 21218 (United States)
  6. Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109 (Australia)
Publication Date:
OSTI Identifier:
21578215
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 736; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/736/2/146; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DATA ANALYSIS; DISTRIBUTION; GALAXIES; RADIAL VELOCITY; STARS; VELOCITY

Citation Formats

Koposov, Sergey E., Gilmore, G., Walker, M. G., Belokurov, V., Evans, N. Wyn, Okamoto, S., Penarrubia, J., Fellhauer, M., Gieren, W., Geisler, D., Monaco, L., Norris, J. E., Wilkinson, M., Wyse, R. F. G., and Zucker, D. B.. ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOOeTES I DWARF SPHEROIDAL GALAXY. United States: N. p., 2011. Web. doi:10.1088/0004-637X/736/2/146.
Koposov, Sergey E., Gilmore, G., Walker, M. G., Belokurov, V., Evans, N. Wyn, Okamoto, S., Penarrubia, J., Fellhauer, M., Gieren, W., Geisler, D., Monaco, L., Norris, J. E., Wilkinson, M., Wyse, R. F. G., & Zucker, D. B.. ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOOeTES I DWARF SPHEROIDAL GALAXY. United States. doi:10.1088/0004-637X/736/2/146.
Koposov, Sergey E., Gilmore, G., Walker, M. G., Belokurov, V., Evans, N. Wyn, Okamoto, S., Penarrubia, J., Fellhauer, M., Gieren, W., Geisler, D., Monaco, L., Norris, J. E., Wilkinson, M., Wyse, R. F. G., and Zucker, D. B.. Mon . "ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOOeTES I DWARF SPHEROIDAL GALAXY". United States. doi:10.1088/0004-637X/736/2/146.
@article{osti_21578215,
title = {ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOOeTES I DWARF SPHEROIDAL GALAXY},
author = {Koposov, Sergey E. and Gilmore, G. and Walker, M. G. and Belokurov, V. and Evans, N. Wyn and Okamoto, S. and Penarrubia, J. and Fellhauer, M. and Gieren, W. and Geisler, D. and Monaco, L. and Norris, J. E. and Wilkinson, M. and Wyse, R. F. G. and Zucker, D. B.},
abstractNote = {We develop, implement, and characterize an enhanced data reduction approach which delivers precise, accurate, radial velocities from moderate resolution spectroscopy with the fiber-fed VLT/FLAMES+GIRAFFE facility. This facility, with appropriate care, delivers radial velocities adequate to resolve the intrinsic velocity dispersions of the very faint dwarf spheroidal (dSph) galaxies. Importantly, repeated measurements let us reliably calibrate our individual velocity errors (0.2 kms{sup -1} {<=} {delta}{sub V} {<=} 5 km s{sup -1}) and directly detect stars with variable radial velocities. We show, by application to the Booetes I dSph, that the intrinsic velocity dispersion of this system is significantly below 6.5 km s{sup -1} reported by previous studies. Our data favor a two-population model of Booetes I, consisting of a majority 'cold' stellar component, with velocity dispersion 2.4{sup +0.9}{sub -0.5} km s{sup -1}, and a minority 'hot' stellar component, with velocity dispersion {approx}9 km s{sup -1}, although we cannot completely rule out a single component distribution with velocity dispersion 4.6{sup 0.8}{sub -0.6} km s{sup -1}. We speculate that this complex velocity distribution actually reflects the distribution of velocity anisotropy in Booetes I, which is a measure of its formation processes.},
doi = {10.1088/0004-637X/736/2/146},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 736,
place = {United States},
year = {2011},
month = {8}
}