arXiv subjects

S. Casertano

Publications and source records attributed to S. Casertano.

43 records · Page 3Linked to original sources

arXiv1999

Near-infrared observations of galaxies in Pisces-Perseus: I. H-band surface photometry of 174 spirals

We present near-infrared, H-band (1.65 um), surface photometry of 174 spiral galaxies in the area of the Pisces-Perseus supercluster. The images, acquired with the ARNICA camera mounted on various telescopes, are used to derive radial profiles of surface brightness, ellipticities, and position angles, together with global parameters such as H-band magnitudes and diameters. The mean relation between H-band isophotal diameter D_{21.5} and the B-band D_{25} implies a B-H color of the outer disk bluer than 3.5; moreover, D_{21.5}/D_{25} depends on (global) color and absolute luminosity. The correlations among the various photometric parameters suggest a ratio between isophotal radius D_{21.5}/2 and disk scale length of about 3.5 and a mean disk central brightness of 17.5 H-mag arcsec^{-2}. We confirm the trend of the concentration index C_{31} with absolute luminosity and, to a lesser degree, with morphological type. We also assess the influence of non-axisymmetric structures on the radial profiles and on the derived parameters.

astro-ph↗

arXiv1999

The Properties of Field Elliptical Galaxies at Intermediate Redshift. I: Empirical Scaling Laws

We present measurements of the Fundamental Plane (FP) parameters (the effective radius, the mean effective surface brightness, and the central velocity dispersion) of six field elliptical galaxies at intermediate redshift. The imaging is taken from the Medium Deep Survey of the Hubble Space Telescope, while the kinematical data are obtained from long-slit spectroscopy using the 3.6-m ESO telescope. The Fundamental Plane appears well defined in the field even at redshift $\approx$ 0.3. The data show a shift in the FP zero point with respect to the local relation, possibly indicating modest evolution, consistent with the result found for intermediate redshift cluster samples. The FP slopes derived for our field data, plus other cluster ellipticals at intermediate redshift taken from the literature, differ from the local ones, but are still consistent with the interpretation of the FP as a result of homology, of the virial theorem and of the existence of a relation between luminosity and mass, $L \propto M^η$. We also derive the surface brightness vs. effective radius relation for nine galaxies with redshift up to $z \approx0.6$, and data from the literature; the evolution that can be inferred is consistent with what is found using the FP.

astro-ph↗

arXiv1998

VLT and HST observations of a candidate high redshift elliptical galaxy in the Hubble Deep Field South

The combined use of the ESO Very Large Telescope (VLT) UT1 Science Verification (SV) images and of the Hubble Space Telescope (HST) Hubble Deep Field South observations allows us to strengthen the identification as a candidate elliptical galaxy of the Extremely Red Object HDFS 223251-603910 previously identified by us on the basis of NICMOS and Cerro Tololo Interamerican Observatory imaging. The photometry presented here includes VLT data in U, B, V, R, I, a STIS unfiltered image, NICMOS J, H, and K band data, thus combining the 16.5 hours of VLT SV exposures with 101 hours of HST observing. The object is detected in all images except the VLT U band and is one of the reddest known with B-K=9.7+-0.5. We consider a wide range of models with different ages, metallicities, star formation histories and dust content, and conclude that the observed spectral energy distribution agrees best with that of an old elliptical galaxy at redshift just below 2. Alternative possibilities are discussed in light of their likelihood and of the perspective of spectroscopic confirmation.

astro-ph↗

arXiv1998

An Extremely Red r^{1/4} Galaxy in the Test Image of the Hubble Deep Field South

We report the serendipitous discovery of an extremely red object in the Hubble Deep Field South (HDFS) Test NICMOS (Near Infrared Camera and Multi Object Spectrograph) field of view. The object is resolved in the NICMOS image and has a light profile very well described by an r^{1/4} law with effective radius r_e=0."20+-0."05 and H_{AB}=21.7+-0.1 magnitudes. In contrast, the galaxy is undetected in the R and I band ground based images taken at the CTIO 4 m Blanco Telescope, giving a lower limit to the color of (R-H)_{AB}>3.9 and (I-H)_{AB}>3.5 at the 95% confidence level. The colors of a range of synthetic galactic spectra are computed, showing that the object is likely to be an ``old'' elliptical galaxy at redshift z>~1.7. Alternatively the colors can be reproduced by an ``old'' elliptical galaxy at somewhat lower redshift (z>~1) with significant amount of dust, or by a younger galaxy at higher redshift. This object represents a very interesting target for future VLT observations.

astro-ph↗

arXiv1997

GAIA and the Hunt for Extra-Solar Planets

We present the results of realistic end-to-end simulations of observations of nearby stars with the proposed global astrometry mission GAIA, recently recommended within the context of ESA's Horizon 2000 Plus long-term scientific program. We show that under realistic, if challenging, assumptions, GAIA will be capable of surveying the solar neighborhood within 100-200 pc for the astrometric signatures of planets around stars down to V = 16 mag. The wealth of results on the frequency and properties of massive planets from GAIA observations will provide a formidable testing ground on which to confront the most sophisticated theories on planetary formation and evolution. Finally, we suggest the possibility of more sophisticated probabilistic detection techniques which may be able to detect the presence of Earth-like planets around stars within 20 pc.

astro-ph↗

arXiv1996

Evidence for Galaxy Interactions/Mergers from Meduim-Deep Survey WFPC2 Data

We examine the morphological and statistical properties of close galaxy pairs from two sets of 28 WFPC2 fields, acquired for the Medium Deep Survey (MDS) and the Groth/Westphal Survey (GWS) in F606W (V) and F814W (I) passbands. In the GWS sample all fields have uniform 95% completeness down to I<=24.3 mag, whereas in the MDS sample, fields have varying 95% completeness limits in the range I<=23.6--24.8 mag. In each field roughly 400 galaxies per 5 square arcminute field are detected. We exploit high resolution WFPC2 images to systematically determine morphological classifications of galaxies as disk- or bulge-dominated down to I<=23 mag (V<=24 mag), and to differentiate galaxies from stars one magnitude fainter. Down to I<=25 mag the number of galaxy pairs with separations less than 3 arcsec is consistent with a shortward extrapolation of the angular two-point correlation function w(theta) proportional to theta^-0.8 observed from the same data; the fraction of such pairs showing morphological evidence for physical association accounts for a third of the total numbers suggested by a shortward extrapolation of w(theta). The latter result may not be too surprising given the low surface brightness of the tidal tails resulting from galaxy interactions, i.e. much of the evidence for interactions may fall below our detection limit. Moreover, we find no trend between apparent physical association (on the basis of morphology) and (V--I) color or I-magnitude difference between pair members of the <3 arcsec-pair sample.

astro-ph↗

arXiv1996

Weak Gravitational Lensing around Field Galaxies in HST Survey Images

Using data from the HST Medium Deep Survey, a long-term Key Project, together with generically similar archived data, we have discovered evidence for weak gravitational `shear' of background field galaxies (I = 22 -- 26) in the vicinity of isolated, foreground galaxies ( I = 15 -- 22), especially those of early type. The statistical lensing is demonstrated by the slight preferential orientation of the major axes of the background galaxies in directions at right angles to the lines joining them to the foreground ones. The detected shear is at the level of $δϕ= 2.5^{o}\pm 1.2^{o}$ averaged over the background galaxies at about ~10 half-light radii from 400 foreground ellipticals, corresponding to a polarization of about 0.04. A positive but less significant result is also reported for foreground spirals. This result excludes the de Vaucouleurs model for the mass distribution of ellipticals, but is consistent with elliptical galaxies having total M/L ~ 100 and extensive dark halos.

astro-ph↗