Browsing by Author "INFANTE, L"

Now showing 1 - 11 of 11
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    A NEW CATALOG OF FAINT GALAXIES
    (1990) INFANTE, L
    A new catalogue of faint galaxies on a 3 deg2 area near the North Galactic Pole (NGP), complete to J = 24.5 and F = 23.5, has been obtained from nine Canada France Hawaii Telescope prime focus plates. The angular correlation function has been measured for the first time to separations approximately 1-degrees. Preliminary results indicate a power law slope of almost-equal-to -0.8 at small separations and no sharp break for theta less-than-or-equal-to 1-degrees. We also find some evidence that the power law slope flattens to fainter limiting magnitudes.
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    A SURVEY OF FAINT GALAXY PAIRS
    (1994) CARLBERG, RG; PRITCHET, CJ; INFANTE, L
    A sample of faint, V-magnitude selected, galaxy pairs, having physical separations less than similar to 20 h(-1) kpc, is used to examine the rise in the merger rate with redshift and the statistical relations between close pairs and the field galaxy population. Redshifts have been obtained for a subset of 14 galaxies (V less than or equal to 22.5) that are in close (theta < 6'') pairs, along with a comparison sample of 38 field galaxies. Two-color photometry is available for 378 galaxies in the same fields. The average redshift of the V less than or equal to 22.5 field population is 0.36, statistically equal to the average redshift of 0.42 for the pairs. The similarity of the two redshift distributions, Delta z less than or equal to 0.1, limits any differential luminosity enhancement of close pairs to less than half a magnitude. The pairs are somewhat bluer than the field and have nearly twice the average [O Pi] detection rate of the field, but the differences are not statistically significant. The field population has an angular correlation at separations of theta less than or equal to 6'' higher than the inward extrapolation of omega(theta) proportional to theta(-0.8), which may be a population of ''companions'' not present at the current epoch, or, luminosity enhancement of intrinsically faint galaxies in pairs. Physical pairs closer than 20 h(-1) kpc comprise similar to 10% of the faint galaxies in our survey fields. The same physical separation applied to local galaxies finds only 4.6% in pairs. If the rise in close, low relative velocity pairs with redshift is parameterized as (1 + z)(m), then m = 3.4 +/- 1.0. If all the pairs merge, then the average galaxy mass would be about 32% smaller at z = 0.4 than locally.
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    ANGULAR-CORRELATION FUNCTION OF FAINT GALAXIES
    (1992) PRITCHET, CJ; INFANTE, L
    The angular correlation function has been computed for a two-color survey Of faint galaxies (J < 24, F < 23) covering a approximately 2.4 deg2 area near the North Galactic Pole. Faint galaxies are found to belong to a population that is more weakly clustered than luminous nearby galaxies, by a factor greater than or similar to 2 at J = 22 and greater than or similar to 4 at J = 24. Objects selected in the F (red) band are closer to model predictions than those observed in the J band. These observations are interpreted in terms of models in which (weakly clustered) bursting dwarf galaxies comprise the bulk of the number counts at faint magnitudes.
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    BV CCD PHOTOMETRY OF THE OLD OPEN CLUSTER NGC 2243
    (1991) BERGBUSCH, PA; VANDENBERG, DA; INFANTE, L
    The color-magnitude diagram (CMD) and luminosity function (LF) of two overlapping fields in NGC 2243, reaching approximately 4 mag below the main-sequence turnoff point, are presented. The photometry has been calibrated using stars from the lists of Landolt and Graham, and is independent of previous work on this cluster. A small clump of horizontal branch stars is evident in the CMD, as is a noticeable gap at V = 16.1 near the turnoff point, but the most striking feature of the CMD is a well defined and populous binary star sequence. Previous estimates of the cluster's metal abundance suggest that it is slightly lower than that of the globular cluster 47 Tuc. A direct comparison of our CMD with the fiducial sequence of 47 Tuc from Hesser et al. [PASP, 99, 739 (1987)], taking into account the slight difference in reddening between the two clusters, produces a good match for the horizontal branch and the unevolved portion of the main sequence. However, because the giant branch of NGC 2243 is redder than that of 47 Tuc, we are led to believe that the open cluster has a slightly higher metal abundance. Assuming the two clusters to have the same abundance parameters, the distance modulus is estimated at (m - M) v = 13.05 from fits to a semiempirical main sequence, and by requiring the two horizontal branches to have the same luminosity. Comparisons with isochrones in the metallicity range - 0.78 less-than-or-equal-to [Fe/H] less-than-or-equal-to 0.47, computed from the latest oxygen enhanced evolutionary sequences, imply a cluster age of 5 +/- 1 Gyr. While all of the isochrones in this metallicity range provide similar fits through the turnoff region, only the [Fe/H] = - 0.47, [O/Fe] = + 0.23 isochrones reproduce the location of the giant branch. The observed LF has a rather flat mass spectrum, with x almost-equal-to - 0.5 in model LFs providing a reasonable fit to the observations. The small gap at V = 16.1 may be associated with the development of the convective hook which follows central hydrogen exhaustion in standard evolutionary models. However, the isochrones neither predict its location correctly nor do they reproduce the morphology of the turnoff region. These discrepancies cannot adequately be explained as the result of the convergence of the single and binary star sequences near the turnoff. Moreover, structure in the observed LF near the turnoff cannot be reproduced even when the binary sequence contribution is included. We suggest that convective overshooting in the cores of moderate mass stars is the probable cause.
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    CLUSTERING OF FAINT GALAXIES
    (1989) INFANTE, L
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    CORRELATION-ANALYSIS OF FAINT GALAXIES
    (1994) INFANTE, L
    As part of a larger study of the clustering properties of galaxies at intermediate redshifts, we present a study of methods and algorithms used to estimate the angular correlation function, omega(theta), of faint galaxies. A technique has been developed which permits the reliable measurement of omega(theta) at amplitude levels as low as approximately 0.002 for fields of area approximately 2 deg2 - i.e. to separations of order 1 degree for galaxies with a blue magnitude almost-equal-to +24. An iterative method has been used to compute the best mean density that ensures consistency between the integral constraint and omega(theta). Artificial galaxy catalogues with built in correlation functions have been analyzed to test for the presence of spurious correlations associated with, for example, field geometry. We conclude that the amplitude and power-law exponent of omega(theta), as well as any outer cutoffs or breaks in omega(theta), are all reliably determined by our algorithm for separations theta less than or similar to 1 degree in catalogues whose angular extent is approximately 2 deg2.
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    COUNTS AND COLORS OF FAINT STARS IN 5 FIELDS NEAR THE NORTH GALACTIC POLE
    (1994) INFANTE, L
    Faint star number counts in the photographic J band and (B - V) colour distributions are presented for a 1.08 deg(2) field near the North Galactic Pole, Due to the excellent star/galaxy discrimination we count stars as faint as J = 23. We compare the number counts and colour distributions in 5 adjacent fields near SA57. The number counts and colour distributions are in very good agreement with previous data. However, we find that the large field-to-field scatter in the colour distributions, which we argue is real, might prevent us setting strong limits on Galactic structure. A simple two component standard model, Bahcall and Soneira (1984), fits the number counts reasonably well at the bright J < 21, but fails notably at the faint end, even if a third component is added, as in Reid and Majewski (1993). The standard models are in good agreement with both the number counts and colour distribution at 20 < V < 21. Although the standard models bimodal shape of the colour distribution compares well with the data at 21 < V < 21.5, the number counts of stars are underestimated.
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    GALAXY COUNTS AND COLORS IN A SOUTH GALACTIC POLE FIELD
    (1986) INFANTE, L; PRITCHET, C; QUINTANA, H
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    THE MEDIUM REDSHIFT CLUSTERS CL-0017-20 AND CL-0500-24
    (1994) INFANTE, L; FOUQUE, P; HERTLING, G; WAY, MJ; GIRAUD, E; QUINTANA, H
    We present magnitudes and redshifts of galaxies in the cluster of galaxies CL 0017-20 and in the double cluster CL 0500-24. Luminosity functions and velocity distributions have been derived. CL 0017-20 possesses a virial mass of 2.9 x 10(14) M(circle dot) and a V band luminosity of 2.3+/-0.5 x 10(12) L(circle dot) (M/L(V) = 127), much of it in a very compact core of size 113 kpc. Our new velocities and photometry of CL 0500-24 confirm its double nature. Our group algorithm clearly detects two subconcentrations with masses 1.9 and 2.2 x 10(14) M(circle dot). Its total V band luminosity amounts to 2.7+/-0.8 x 10(12) L(circle dot) (M/L(V) of 157). Since the crossing and collapse times in both clusters are smaller than the age of the Universe, they appear bound and virialized. It is surprising that although M/L is small in these clusters, giant arcs have been detected in both.