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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 galaxys 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.
We study the star formation (SF) law in 12 Galactic molecular clouds with ongoing high-mass star formation (HMSF) activity, as traced by the presence of a bright IRAS source and other HMSF tracers. We define the molecular cloud (MC) associated to eac
We report the discovery of the most metal-poor dwarf star-forming galaxy (SFG) known to date, J0811+4730. This galaxy, at a redshift z=0.04444, has a Sloan Digital Sky Survey (SDSS) g-band absolute magnitude M_g = -15.41 mag. It was selected by inspe
Three bright molecular line sources in G333 have recently been shown to exhibit signatures of infall. We describe a molecular line radiative transfer modelling process which is required to extract the infall signature from Mopra and Nanten2 data. The
We study the hierarchical stellar structures in a $sim$1.5 deg$^2$ area covering the 30 Doradus-N158-N159-N160 star-forming complex with the VISTA Survey of the Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface
We present results of a multi-epoch monitoring program on variability of 6$,$cm formaldehyde (H$_2$CO) masers in the massive star forming region NGC$,$7538$,$IRS$,$1 from 2008 to 2015 conducted with the GBT, WSRT, and VLA. We found that the similar v