Related papers: Crowded-field photometry from HST-imaging
We have obtained HST-NICMOS observations of five of M31's most metal rich globular clusters. These data allow photometry of individual stars in the clusters and their surrounding fields. However, to achieve our goals -- obtain accurate…
We explore the limits of photometric reductions of crowded stellar fields observed with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Two photometric procedures, based on the DoPHOT and DAOPHOT/ALLFRAME programs…
We use star counts from 13 deep HST fields imaged with the {\it Wide Field Camera - 2} in order to constrain the amount of dark matter in the Galaxy that can be in the form of low-mass main sequence stars or white-dwarfs. Based on the…
We present a study of the effect of crowding on stellar photometry. We develop an analytical model through which we are able to predict the error in magnitude and color for a given star for any combination of telescope resolution, stellar…
The images provided by the Advanced Camera for Surveys at the Hubble Space Telescope (ACS/HST) have the amazing spacial resolution of 0".05/pixel. Therefore, it is possible to resolve individual stars in nearby galaxies and, in particular,…
The identification of individual stars in crowded environments using photometric information alone is confounded by source confusion. However, with the addition of spectroscopic information it is possible to distinguish between blends and…
A study of aperture size effects on star cluster photometry in crowded fields is presented. Tests were performed on a sample of 285 star cluster candidates in the South-West field of the M31 galaxy disk, measured in the Local Group Galaxy…
We analyse a sample of over 1000 stars from 32 fields imaged in the V and I bands with the Wide Field and Planetary Camera, on board of the Hubble Space Telescope. The fields are located at Galactic latitudes | b | >= 15deg and in various…
We present an analysis of the deepest pure-UV observations with the highest angular resolution ever performed, a set of 12 exposures with the HST WFPC2 and F160BW filter obtained in parallel observing mode, which cover $\sim$12 square…
We present HST imaging of eight spectroscopically-confirmed giant arcs, pairs and arclets. These objects have all been extensively studied from the ground and we demonstrate the unique advantages of HST imaging in the study of such features…
CONTEXT. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. AIMS. I study a sample of massive stars with high angular resolution to better…
WFIRST microlensing observations will return high-precision parallaxes, sigma(pi) < 0.3 microarcsec, for the roughly 1 million stars with H<14 in its 2.8 deg^2 field toward the Galactic bulge. Combined with its 40,000 epochs of high…
We examine a caustic-straddling arc at $z=0.9397$ in the field of the galaxy cluster MACS J0416.1-2403 ($z=0.397$) using archival multiband HST images and show that its surface brightness exhibits anomalies that can be explained by a single…
We report high spatial resolution HST imagery and photometry of three well-studied, intense galactic X-ray binaries, X2129+47, CAL 87 and GX17+2. All three sources exhibit important anomalies, not readily interpreted by conventional models.…
Upcoming next-generation sky surveys will detect large number of faint objects with magnitudes larger than 25. When objects are crowded within a limited a field of view, blending becomes unavoidable. Blending leads to the omission of many…
Star clusters in 6 nearby spiral galaxies are examined using archive images from HST/WFPC2. The galaxies have previously been studied from the ground and some of them are known to possess rich populations of "young massive clusters" (YMCs).…
We have developed photometric techniques that can be applied to images with highly-variable backgrounds, as well as to slightly-extended objects (object size comparable to or smaller than PSF size). We have shown that ordinary stellar…
HST-WFPC2 F555W and F814W photometry were obtained for 16 fields of the luminous nearby spiral galaxy M31, sampling the stellar content of the disk and the halo at different distances from the center, from ~ 20 to ~ 150 arcmin (i.e. ~ 4.5…
We present photometry from Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 parallel imagery of a remote M31 field at a projected distance of about 34 kpc from the nucleus near the SW major axis. This field is near the globular…
We present BVI CCD photometry for more than 10,000 stars in the innermost region (0.3' < r <~ 4') of the globular cluster M 3. When added to the previous photographic photometry by Buonanno et al. (1994) reaching as far as r ~ 7', this…