We study the nature of faint, red-selected galaxies at z ∼ 2 − 3 using the Hubble Ultra Deep Field (HUDF) and Spitzer Infrared Array Camera (IRAC) photometry. Given the magnitude limit of the HST data, we detect candidate galaxies to HAB < 26 mag, probing lower-luminosity (lower mass) galaxies at these redshifts. We identify 32 galaxies satisfying the (J110 − H160)AB > 1.0 mag color selection, ...

We present an analysis of the stellar populations as a function of mass in a sample of ∼7000 galaxies of all morphological and emission types from the 6dF Galaxy Survey (6dFGS). We measure velocity dispersions and Lick indices from the spectra of the central regions of these galaxies, deriving ages and metallicities from the Lick indices using stellar population models. We also derive dynamical...

Agency ABSTRACT We present HST NICMOS photometry of the resolved stellar population in the dwarf irregular galaxy NGC 1569. The color-magnitude diagram (CMD) in the F110W and F160W photometric bands contains ∼2400 stars with a formal photometric error ∼ < 0.1 mag down to m F110W ≈ 23.5 and m F160W ≈ 22.5. The fiducial photometry has a completeness factor higher than 50% down to m F110W ≈ 21.5 a...

We present the broad-band UV through mid-infrared spectral energy distributions (SEDs) of a sample of 72 spectroscopically-confirmed star-forming galaxies at z = 2.30± 0.3. Located in a 72 arcmin field centered on the bright background QSO, HS1700+643, these galaxies were pre-selected to lie at z ∼ 2 based solely on their rest-frame UV colors and luminosities, and should be representative of UV...

The effects of stellar rotation on the photometric derivation of atmospheric parameters, ages and masses of main sequence B7-A4 stars are evaluated.Monte-Carlo simulations, used to generate a sample in themass range 1-5 M with all necessary individual rotational parameters and fundamental quantities, and the corrections on the photometric indices proposed by Collins & Sonneborn (1977), provide ...

Aims. We investigate the intermediate-age asymptotic giant branch stellar population of two Local Group dwarf irregular galaxies to characterize their carbon star population in near-infrared (IR). Methods. Our work is based on near-IR photometry complemented with optical ground based and Hubble Space Telescope (HST) photometry. Near-IR photometry is based on our and archival J and Ks-band image...

Encircling the Milky Way at low latitudes, the Low Latitude Stream is a large stellar structure, the origin of which is as yet unknown. As part of the SEGUE survey, several photometric scans have been obtained that cross the Galactic plane, spread over a longitude range of 50◦ to 203◦. These data allow a systematic study of the structure of the Galaxy at low latitudes, where the Low Latitude St...

We present projected velocity dispersion profiles for the Draco and Ursa Minor (UMi) dwarf spheroidal galaxies based on 207 and 162 discrete stellar velocities, respectively. Both profiles show a sharp decline in the velocity dispersion outside ∼ 30 (Draco) and ∼ 40 (UMi). New, deep photometry of Draco reveals a break in the light profile at ∼ 25. These data imply the existence of a kinematical...

Gravitational microlensing is a new technique for studying the surfaces of distant stars. A point mass lens, usually a low-mass star from the disk, will typically resolve the surface of a red giant in the Galactic bulge, as well as amplify its brightness by a factor of 10 or more. Such events are now detected in real time and can be followed up with precision photometry and spectroscopy. The mo...

We explore mechanisms for the regulation of star formation in dwarf galaxies. We concentrate primarily on a sample in the Virgo cluster, which has HI and blue total photometry, for which we collected Hα data at the Wise Observatory. We find that dwarf galaxies do not show the tight correlation of the surface brightness of Hα (a star formation indicator) with the HI surface density, or with the ...