We have used deep images from the Hubble Space Telescope to study the evolution in the morphologies, sizes, stellar–masses, colors, and internal color dispersion of galaxies in the Hubble Deep Field North. We selected two galaxy samples at 0.7 ≤ z ≤ 1.4 and 1.9 ≤ z ≤ 3.0 from a near–infrared, flux–limited catalog with complete photometric and spectroscopic redshift information. At z ∼ 1 the maj...

We study the chemical and kinematic properties of the first galaxies which formed at a high redshift, using high resolution cosmological numerical simulations, and compared them with the recent observational results for the Sculptor dwarf spheroidal galaxy by Tolstoy et al., who found two distinct stellar populations: the lower metallicity stars are more spatially extended and possess a higher ...

We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/IRAC imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star formation, as traced by PAH emission, with measured star formation rates that compare well to those estimated from ot...

Studying the stellar populations in the outskirts of spiral galaxies can provide important constraints on their structure, formation, and evolution. To that end, we present VI photometry obtained with the Advanced Camera for Surveys for three fields located ∼ 20 − 30 in projected distance southeast of M33’s nucleus (corresponding to ∼ 4 − 6 visual scale lengths or ∼ 9 − 13 kpc in deprojected ra...

Surface photometry detections of red and exceedingly faint halos around galaxies have resurrected the old question of whether some non-negligible fraction of the missing baryons of the Universe could be hiding in the form of faint, hydrogen-burning stars. The optical/near-infrared colours of these red halos have proved very difficult to reconcile with any normal type of stellar population, but ...

The tightness of the observed colour-magnitude and Mg2velocity dispersion relations for elliptical galaxies has often been cited as an argument against a picture in which ellipticals form by the merging of spiral disks. A common view is that merging would mix together stars of disparate ages and produce a large scatter in these relations. Here I use semi-analytic models of galaxy formation to d...

We analyze very deep HST, VLT and Spitzer photometry of galaxies at 2 < z < 3.5 in the Hubble Deep Field South. The sample is selected from the deepest public K-band imaging currently available. We show that the rest-frame U−V vs V −J color-color diagram is a powerful diagnostic of the stellar populations of distant galaxies. Galaxies with red rest-frame U − V colors are generally red in restfr...

We present integrated optical spectrophotometry for a sample of 417 nearby galaxies. Our observations consist of spatially integrated, S/N = 10− 100 spectroscopy between 3600 and 6900 Å at ∼ 8 Å FWHM resolution. In addition, we present nuclear (2. 5 × 2. 5) spectroscopy for 153 of these objects. Our sample targets a diverse range of galaxy types, including starbursts, peculiar galaxies, interac...

We report on observations of the stellar populations in twelve fields spanning the region between the Magellanic Clouds, made with the Mosaic-II camera on the 4-meter telescope at the Cerro-Tololo Inter-American Observatory. The two main goals of the observations are to characterize the young stellar population (which presumably formed in situ in the Bridge and therefore represents the nearest ...

Using deep near–infrared and optical observations of the Hubble Deep Field North from the Hubble Space Telescope NICMOS and WFPC2 instruments and from the ground, we examine the spectral energy distributions of Lyman break galaxies (LBGs) at 2.0 . z . 3.5 in order to investigate their stellar population properties. The ultraviolet–to–optical rest–frame spectral energy distributions (SEDs) of th...