Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 1, 2012 | Published
Journal Article Open

A unique isolated dwarf spheroidal galaxy at D = 1.9 Mpc

Abstract

We present a photometric and spectroscopic study of the unique isolated nearby dwarf spheroidal (dSph) galaxy KKR 25. The galaxy was resolved into stars with Hubble Space Telescope/Wide Field Planetary Camera 2 including old red giant branch and red clump. We have constructed a model of the resolved stellar populations and measured the star formation rate and metallicity as a function of time. The main star formation activity period occurred about 12.6–13.7 Gyr ago. These stars are mostly metal poor, with a mean metallicity [Fe/H] ∼ −1 to −1.6 dex. About 60 per cent of the total stellar mass was formed during this event. There are indications of intermediate-age star formation in KKR 25 between 1 and 4 Gyr with no significant signs of metal enrichment for these stars. Long-slit spectroscopy was carried out using the Russian 6-m telescope of the integrated starlight and bright individual objects in the galaxy. We have discovered a planetary nebula (PN) in KKR 25. This is the first known PN in a dSph galaxy outside the Local Group. We have measured its oxygen abundance 12 + log (O/H) = 7.60 ± 0.07 dex and a radial velocity V_h = −79 km s^(−1). We have analysed the stellar density distribution in the galaxy body. The galaxy has an exponential surface brightness profile with a central light depression. We discuss the evolutionary status of KKR 25, which belongs to a rare class of very isolated dwarf galaxies with spheroidal morphology.

Additional Information

© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 June 23. Received 2012 June 11; in original form 2012 April 9. We are thankful to Dr S. Pustilnik for very useful discussions of our work. We acknowledge the usage of the HyperLEDA data base (http://leda.univ-lyon1.fr). STSDAS is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. The work was supported by the Russian Foundation for Basic Research (RFBR) grant 11-02-00639, Russian–Ukrainian RFBR grant 11-02-90449 and the programme no. 17 'Active processes in galactic and extragalactic objects' of the Department of Physical Sciences of the Russian Academy of Sciences. We acknowledge the support of the Ministry of Education and Science of the Russian Federation, contract 14.740.11.0901.

Attached Files

Published - mnr21581.pdf

Files

mnr21581.pdf
Files (2.0 MB)
Name Size Download all
md5:63f7a09cb3f277b7fdd1c2e75f367736
2.0 MB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023