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Title: STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY

Abstract

We present kinematical profiles and metallicity for the M31 dwarf spheroidal (dSph) satellite galaxy Andromeda II (And II) based on Keck DEIMOS spectroscopy of 531 red giant branch stars. Our kinematical sample is among the largest for any M31 satellite and extends out to two effective radii (r {sub eff} = 5.'3 = 1.1 kpc). We find a mean systemic velocity of -192.4 {+-} 0.5 km s{sup -1} and an average velocity dispersion of {sigma} {sub v} = 7.8 {+-} 1.1 km s{sup -1}. While the rotation velocity along the major axis of And II is nearly zero (<1 km s{sup -1}), the rotation along the minor axis is significant with a maximum rotational velocity of v {sub max} = 8.6 {+-} 1.8 km s{sup -1}. We find a kinematical major axis, with a maximum rotational velocity of v {sub max} = 10.9 {+-} 2.4 km s{sup -1}, misaligned by 67 Degree-Sign to the isophotal major axis. And II is thus the first dwarf galaxy with evidence for nearly prolate rotation with a v {sub max}/{sigma} {sub v} = 1.1, although given its ellipticity of {epsilon} = 0.10, this object may be triaxial. We measured metallicities for a subsample ofmore » our data, finding a mean metallicity of [Fe/H] = -1.39 {+-} 0.03 dex and an internal metallicity dispersion of 0.72 {+-} 0.03 dex. We find a radial metallicity gradient with metal-rich stars more centrally concentrated, but do not observe a significant difference in the dynamics of the two metallicity populations. And II is the only known dwarf galaxy to show minor axis rotation, making it a unique system whose existence offers important clues on the processes responsible for the formation of dSphs.« less

Authors:
; ;  [1];  [2];  [3];  [4];  [5];  [6]; ;  [7]
  1. Astronomy Department, Yale University, New Haven, CT 06520 (United States)
  2. Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)
  3. UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)
  4. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  5. Department of Astronomy, University of Washington, Seattle, WA 98195 (United States)
  6. Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
  7. Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States)
Publication Date:
OSTI Identifier:
22086504
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 758; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; EMISSION SPECTROSCOPY; GALAXIES; GIANT STARS; HYDROGEN; IRON; ROTATION; VELOCITY

Citation Formats

Ho, Nhung, Geha, M., Tollerud, E., Munoz, R. R., Guhathakurta, P., Kalirai, J., Gilbert, K. M., Bullock, J., Beaton, R. L., and Majewski, S. R., E-mail: ngocnhung.ho@yale.edu, E-mail: marla.geha@yale.edu. STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY. United States: N. p., 2012. Web. doi:10.1088/0004-637X/758/2/124.
Ho, Nhung, Geha, M., Tollerud, E., Munoz, R. R., Guhathakurta, P., Kalirai, J., Gilbert, K. M., Bullock, J., Beaton, R. L., & Majewski, S. R., E-mail: ngocnhung.ho@yale.edu, E-mail: marla.geha@yale.edu. STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY. United States. doi:10.1088/0004-637X/758/2/124.
Ho, Nhung, Geha, M., Tollerud, E., Munoz, R. R., Guhathakurta, P., Kalirai, J., Gilbert, K. M., Bullock, J., Beaton, R. L., and Majewski, S. R., E-mail: ngocnhung.ho@yale.edu, E-mail: marla.geha@yale.edu. Sat . "STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY". United States. doi:10.1088/0004-637X/758/2/124.
@article{osti_22086504,
title = {STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY},
author = {Ho, Nhung and Geha, M. and Tollerud, E. and Munoz, R. R. and Guhathakurta, P. and Kalirai, J. and Gilbert, K. M. and Bullock, J. and Beaton, R. L. and Majewski, S. R., E-mail: ngocnhung.ho@yale.edu, E-mail: marla.geha@yale.edu},
abstractNote = {We present kinematical profiles and metallicity for the M31 dwarf spheroidal (dSph) satellite galaxy Andromeda II (And II) based on Keck DEIMOS spectroscopy of 531 red giant branch stars. Our kinematical sample is among the largest for any M31 satellite and extends out to two effective radii (r {sub eff} = 5.'3 = 1.1 kpc). We find a mean systemic velocity of -192.4 {+-} 0.5 km s{sup -1} and an average velocity dispersion of {sigma} {sub v} = 7.8 {+-} 1.1 km s{sup -1}. While the rotation velocity along the major axis of And II is nearly zero (<1 km s{sup -1}), the rotation along the minor axis is significant with a maximum rotational velocity of v {sub max} = 8.6 {+-} 1.8 km s{sup -1}. We find a kinematical major axis, with a maximum rotational velocity of v {sub max} = 10.9 {+-} 2.4 km s{sup -1}, misaligned by 67 Degree-Sign to the isophotal major axis. And II is thus the first dwarf galaxy with evidence for nearly prolate rotation with a v {sub max}/{sigma} {sub v} = 1.1, although given its ellipticity of {epsilon} = 0.10, this object may be triaxial. We measured metallicities for a subsample of our data, finding a mean metallicity of [Fe/H] = -1.39 {+-} 0.03 dex and an internal metallicity dispersion of 0.72 {+-} 0.03 dex. We find a radial metallicity gradient with metal-rich stars more centrally concentrated, but do not observe a significant difference in the dynamics of the two metallicity populations. And II is the only known dwarf galaxy to show minor axis rotation, making it a unique system whose existence offers important clues on the processes responsible for the formation of dSphs.},
doi = {10.1088/0004-637X/758/2/124},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 758,
place = {United States},
year = {2012},
month = {10}
}