Related papers: Very metal poor Classical Cepheids: variables in I…

We report two new low metallicity blue compact dwarf galaxies (BCDs), WISEP J080103.93+264053.9 (hereafter W0801+26) and WISEP J170233.53+180306.4 (hereafter W1702+18), discovered using the Wide-field Infrared Survey Explorer (WISE). We…

We report the discovery of broad Wolf-Rayet emission lines in the Multiple Mirror Telescope (MMT) spectrum of the NW component of I Zw 18, the lowest-metallicity blue compact dwarf (BCD) galaxy known. Two broad Wolf-Rayet (W-R) bumps at the…

We investigate the theoretical scenario concerning the large sample of variables recently discovered in the dwarf, metal-poor irregular galaxy Leo A, focusing the attention on the "Anomalous" Cepheid phenomenon and its correlation with RR…

We revisited the short period Type II Cepheids (T2Cs), called the BL Herculis (BLHs), in the Galactic Field to derive a homogeneous analysis of their Fourier parameters. Only V-band data were compiled to make sure that it was directly…

The first results are presented of a four-year program dedicated to the CCD observations of Cepheids in the nearby galaxy IC 1613. Since the program was carried out with a relatively small telescope, the Dutch 0.9 m at ESO-La Silla, the…

We present results of the search for Cepheids in the galaxy IC1613 carried out as a sub-project of the OGLE-II microlensing survey. 138 Cepheids were found in the 14.2x14.2 arcmin region in the center of the galaxy. We present light curves,…

(abridged): Using HST and ground-based optical and NIR imaging data, we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18 possesses an extended low-surface-brightness (LSB) old stellar population underlying its star-forming…

We present a {\em Spitzer}-based mid-infrared study of a large sample of Blue Compact Dwarf galaxies (BCD) using the Infrared Spectrograph (IRS), including the first mid-IR spectrum of IZw18, the archetype for the BCD class and among the…

I Zw 18 is a prototype Blue Compact Dwarf (BCD), characterized by a strong starburst and extremely low metallicity (Z ~ 0.02 Zsun). It has long been considered a candidate young galaxy in the Local Universe, but recent studies indicate the…

Classical Cepheids are the most popular distance indicators and tracers of young stellar populations. The key advantage is that they are bright and they can be easily identified in Local Group and Local Volume galaxies. Their evolutionary…

We present V and I photometry of the resolved stars in the most metal-deficient blue compact dwarf galaxy known, I Zw 18 (Zsun/50), using Hubble Space Telescope/Advanced Camera for Surveys (ACS) images, the deepest ones ever obtained for…

Understanding how galaxies formed their first stars is a vital cosmological question, but the study of high-redshift objects, caught in the act of forming their first stars, is difficult. Here we argue that two extremely low-metallicity…

Blue compact dwarf galaxies (BCDs) are faint (M(B) < -17 mag) compact (R <1 kpc), at least qualitatively very blue galaxies due to active star formation, and have low metallicities. Found serendipitously as part of a redshift survey of…

The blue compact dwarf galaxy I Zw 18 is one of the most metal poor systems known in the local Universe (12 + log(O/H) $=$ 7.17). In this work we study I Zw 18 using data from {\it Spitzer}, {\it Herschel Space Telescope} and IRAM Plateau…

We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our…

New spectroscopic observations of the metal poor galaxy IZw 18 are discussed. Wolf-Rayet stars of WC type have been detected in the NW-HII region contrary to evolutionary synthesis model predictions. Implications on the mass loss rate and…

(Abridged) We present the results of a new search for variable stars in the Local Group (LG) isolated dwarf galaxy IC1613, based on 24 orbits of F475W and F814W photometry from the ACS camera onboard the HST. We detected 259 candidate…

Wolf-Rayet stars (WR) have been detected in the NW region of the metal-poor starburst galaxy IZw 18. The integrated luminosity and FWHM of the bumps at 4650 A and 5808 A are consistent with the presence of a few individual stars of WC4 or…

Anomalous Cepheids (ACs) are less studied metal-poor pulsating stars ([Fe/H]<-1.5) compared to Classical Cepheids (CCs) and RR Lyrae stars. They follow distinct Period-Luminosity (PL) and Period-Wesenheit (PW) relations and pulsate in…

We have discovered a sample of 17 metal-poor, yet luminous, star-forming galaxies at redshifts z~0.7. They were selected from the initial phase of the DEEP2 survey of 3900 galaxies and the Team Keck Redshift Survey (TKRS) of 1536 galaxies…