Variability and star formation in Leo T, the lowest luminosity star-forming galaxy known today

Дата и время публикации : 2012-07-11T20:00:00Z

Авторы публикации и институты :
Gisella Clementini (INAF, Osservatorio Astronomico di Bologna, Italy)
Michele Cignoni (INAF, Osservatorio Astronomico di Bologna, Italy, Dipartimento di Astronomia, Universita’ di Bologna, Italy)
Rodrigo Contreras Ramos (INAF, Osservatorio Astronomico di Bologna, Italy, Dipartimento di Astronomia, Universita’ di Bologna, Italy)
Luciana Federici (INAF, Osservatorio Astronomico di Bologna, Italy)
Vincenzo Ripepi (INAF, Osservatorio Astronomico di Capodimonte, Napoli, Italy)
Marcella Marconi (INAF, Osservatorio Astronomico di Capodimonte, Napoli, Italy)
Monica Tosi (INAF, Osservatorio Astronomico di Bologna, Italy)
Ilaria Musella (INAF, Osservatorio Astronomico di Capodimonte, Napoli, Italy)

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 31 pages, 14 figures, accepted for publication in ApJ
Первичная категория: astro-ph.GA

Все категории : astro-ph.GA, astro-ph.SR

Краткий обзор статьи: We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way (MW) "ultra-faint" dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 10 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409 $^{+29}_{-27}$ kpc (distance modulus of 23.06 $pm$ 0.15 mag) was derived from the galaxy’s RR Lyrae star. Our V, V-I color-magnitude diagram of Leo T reaches V~29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the star formation history, based on the comparison of the observed V,V-I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex star formation history dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.

Category: Physics