Browsing by Author "Maza, J"

Now showing 1 - 5 of 5
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    Cataclysmic variables from the Calan-Tololo Survey - I. Photometric periods
    (2004) Tappert, C; Augusteijn, T; Maza, J
    In a search for cataclysmic variables in the Calan-Tololo Survey, we have detected 21 systems, 16 of them previously unknown. In this paper we present detailed time-series photometry for those six confirmed cataclysmic variables that show periodic variability in their light curves. Four of them turned out to be eclipsing systems, while the remaining two show a modulation consisting of two humps. All derived periods are below or, in one case, just at the lower edge of the period gap.
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    The luminous Type Ic supernova 1992ar at z=0.145
    (2000) Clocchiatti, A; Phillips, MM; Suntzeff, NB; DellaValle, M; Cappellaro, E; Turatto, M; Hamuy, M; Avilés, R; Navarrete, M; Smith, C; Rubenstein, EP; Covarrubias, R; Stetson, PB; Maza, J; Riess, AG; Zanin, C
    We present spectroscopic and photometric observations of SN 1992ar, the most distant supernova (SN) in the Calan/Tololo Survey. We compare its spectrum with those of nearby Type Ia and Ic SNe and conclude that the latter type is a better match to SN 1992ar. Using K-corrections based on the spectra of well-observed Type Ic and Ia SNe, we compute different possible rest-frame light curves of SN 1992ar and compare them with those of representative SNe of each type observed in the nearby universe. From the photometry and the spectra, we are able to conclude that SN 1992ar cannot be matched by any known example of a Type Ia SN. Even though the data set collected is fairly complete (one spectrum and 10 photometric points), it is not possible to decide whether SN 1992ar was a fast Type Ic SN, like SN 1994I, or a slow one, like SN 1983V. The absolute V magnitudes at maximum implied by each of these possibilities are -19.2 and -20.2, respectively. The latter would make SN 1992ar one of the brightest SNe on record. SN 1992ar, hence, illustrates the problem of contamination faced by the high-z Type Ia SNe samples whose luminosity distances are used to determine the cosmological parameters of the universe. We, present observational criteria to distinguish the two SN types when the Si II 6355 Angstrom line is redshifted out of the sensitivity range of typical CCD detectors and discuss the effect that these luminous Type Ic SNe would have on the measured cosmological parameters, if not removed from the high-z Type Ia SN samples.
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    The multiwavelength survey by Yale-Chile (MUSYC)
    (2006) Gawiser, E; van Dokkum, PG; Herrera, D; Maza, J; Castander, FJ; Infante, L; Lira, P; Quadri, R; Toner, R; Treister, E; Urry, CM; Altmann, M; Assef, R; Christlein, D; Coppi, PS; Durán, MF; Franx, M; Galaz, G; Huerta, L; Liu, C; López, S; Méndez, R; Moore, DC; Rubio, M; Ruiz, MT; Toft, S; Yi, SK
    We present UBVRIz' optical images taken with MOSAIC on the CTIO 4 m telescope of the 0.32 deg(2) Extended Hubble Deep Field-South. This is one of four fields comprising the MUSYC survey, which is optimized for the study of galaxies at z=3, active galactic nucleus (AGN) demographics, and Galactic structure. Our methods used for astrometric calibration, weighted image combination, and photometric calibration in AB magnitudes are described. We calculate corrected aperture photometry and its uncertainties and find through tests that these provide a significant improvement upon standard techniques. Our photometric catalog of 62,968 objects is complete to a total magnitude of R-AB=25, with R-band counts consistent with results from the literature. We select z similar or equal to 3 Lyman break galaxy (LBG) candidates from their UVR colors and find a sky surface density of 1.4 arcmin(-2) and an angular correlation function w(theta) (2.3 +/- 1.0)theta(-0.8), consistent with previous findings that high-redshift Lyman break galaxies reside in massive dark matter halos. Our images and catalogs are available online.
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    The peculiar type II supernova 1997D
    (1998) Turatto, M; Mazzali, PA; Young, TR; Nomoto, K; Iwamoto, K; Benetti, S; Cappellaro, E; Danziger, IJ; de Mello, DF; Phillips, MM; Suntzeff, NB; Clocchiatti, A; Piemonte, A; Leibundgut, B; Covarrubias, R; Maza, J; Sollerman, J
    SN 1997D in NGC 1536 is possibly the least luminous and energetic Type II supernova discovered to date. The entire light curve is subluminous, never reaching M-v = -14.65. The radioactive tail follows the Co-56 decay slope. In the case of a nearly complete trapping of the gamma-rays, the Ni-56 mass derived from the tail brightness is extremely small, similar to 0.002 M.. At discovery, the spectra showed a red continuum and line velocities on the order of 1000 km s(-1). The luminosity and the photospheric expansion velocity suggest that the explosion occurred about 50 days before discovery and that a plateau probably followed. Model light curves and spectra of the explosion of a 26 M. star successfully fitted the observations. Low-mass models are inconsistent with the observations. The radius of the progenitor, constrained by the prediscovery upper limits, is R-0 less than or similar to 300 R.. A low explosion energy of similar to 4 x 10(50) ergs is then required in the modeling. The strong Pa II lines in the photospheric spectra are reproduced with a solar abundance and low T-eff. A scenario in which the low Ni-56 mass observed in SN 1997D is due to fallback of material onto the collapsed remnant of the explosion of a 25-40 M. star appears to be favored over the case of the explosion of an 8-10 M. star with low Ni-56 production.
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    The physical nature of Lyα-emitting galaxies at z=3.1
    (2006) Gawiser, E; van Dokkum, PG; Gronwall, C; Ciardullo, R; Blanc, GA; Castander, FJ; Feldmeier, J; Francke, H; Franx, M; Haberzettl, L; Herrera, D; Hickey, T; Infante, L; Lira, P; Maza, J; Quadri, R; Richardson, A; Schawinski, K; Schirmer, M; Taylor, EN; Treister, E; Urry, CM; Virani, SN
    We selected 40 candidate Ly alpha-emitting galaxies ( LAEs) at z similar or equal to 3.1 with observed-frame equivalent widths greater than 150 and inferred emission-line fluxes above 2.5 x 10(-17) ergs cm(-2) s(-1) from deep narrowband and broadband MUSYC images of the Extended Chandra Deep Field South. Covering 992 arcmin(2), this is the largest "blank field" surveyed for LAEs at z similar to 3, allowing an improved estimate of the space density of this population of ( 3 +/- 1) x 10(-4) h(70)(3) Mpc(-3). Spectroscopic follow-up of 23 candidates yielded 18 redshifts, all at z similar or equal to 3.1. Over 80% of the LAEs are dimmer in continuum magnitude than the typical Lyman break galaxy ( LBG) spectroscopic limit of R = 25.5 ( AB), with a median continuum magnitude R similar or equal to 27 and very blue continuum colors, V-z similar or equal to 0. Over 80% of the LAEs have the right UVR colors to be selected as LBGs, but only 10% also have R <= 25.5. Stacking the UBVRIzJK fluxes reveals that LAEs have stellar masses similar or equal to 5 x 10(8) h(70)(-2) M-circle dot and minimal dust extinction, A(V) less than or similar to 0.1. Inferred star formation rates are similar or equal to 6 h(70)(-2) M-circle dot yr(-1), yielding a cosmic star formation rate density of 2 x 10(-3) h(70) M-circle dot yr(-1) Mpc(-3). None of our LAE candidates show evidence for rest-frame emission-line equivalent widths EWrest > 240 (A) over circle that might imply a nonstandard initial mass function. One candidate is detected by Chandra, implying an AGN fraction of 2% +/- 2% for LAE candidate samples. In summary, LAEs at z similar to 3 have rapid star formation, low stellar mass, little dust obscuration, and no evidence for a substantial AGN component.