Browsing by Subject "star-formation history"
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Item Converting From 3.6 And 4.5 Micron Fluxes To Stellar Mass(2012-06) Eskew, Michael; Zaritsky, Dennis; Meidt, Sharon; Eskew, MichaelWe use high spatial resolution maps of stellar mass and infrared flux of the Large Magellanic Cloud (LMC) to calibrate a conversion between 3.6 and 4.5 mu m fluxes and stellar mass, M-* = 10(5.65) F-3.6(2.85) F-4.5(-1.85) (D/0.05)(2) M-circle dot,where fluxes are in Jy and D is the luminosity distance to the source in Mpc, and to provide an approximate empirical estimate of the fractional internal uncertainty in M* of 0.3 root N/10(6), where N is the number of stars in the region. We find evidence that young stars and hot dust contaminate the measurements, but attempts to remove this contamination using data that are far superior to what are generally available for unresolved galaxies resulted in marginal gains in accuracy. The scatter among mass estimates for regions in the LMC is comparable to that found by previous investigators when modeling composite populations, and so we conclude that our simple conversion is as precise as possible for the data and models currently available. Our results allow for a reasonably bottom-heavy initial mass function, such as Salpeter or heavier, and moderately disfavor lighter versions such as a diet-Salpeter or Chabrier initial mass function.Item Massive Z Similar To 1.3 Evolved Galaxies Revealed(2003-01) Saracco, P.; Longhetti, M.; Severgnini, P.; Della Ceca, R.; Mannucci, F.; Bender, R.; Drory, N.; Feulner, G.; Ghinassi, F.; Hopp, U.; Maraston, C.; Drory, N.We present the results of TNG near-IR low resolution spectroscopy of two (S7175_254 and S7F5_45) sources belonging to a complete sample of 15 EROs with K' < 18 and R - K' > 5 selected from the MUNICS Survey. Both the spectra show a sharp drop in the continuum which can be ascribed only to the Balmer break. This places them at 1.2 < z < 1.5. Their rest-frame z = 1.2 K-band absolute magnitude is M-K similar or equal to -26.6 (L - 7L*). The comparison of the spectra and the photometric data with a grid of synthetic template spectra provides a redshift z similar or equal to 1.22(+0.02)(-0.07) for S7175_254 and z similar or equal to 1.46 +/- 0.02 for S7175_45. The resulting lower limits to their stellar mass are M-stars(min) = 6 x 10(11) M. and M-stars(min) = 4 x 10(11) M.. The minimum age of the last burst of star formation in S7F5_254 is 3.5 Gyr while it is 0.5 Gyr in S7F5_45 implying a minimum formation redshift z(f) greater than or similar to 3.5 and z(f) greater than or similar to 2 for the two EROs respectively.Item A Measurement Of The Rate Of Type Ia Supernovae At Redshift Z Approximate To 0.1 From The First Season Of The SDSS-II Supernova Survey(2008-07) Dilday, Benjamin; Kessler, Richard; Frieman, Joshua A.; Holtzman, Jon; Marriner, John; Miknaitis, Gajus; Nichol, Robert C.; Romani, Roger; Sako, Masao; Bassett, Bruce; Becker, Andrew; Cinabro, David; DeJongh, Fritz; Depoy, Darren L.; Doi, Mamoru; Garnavich, Peter M.; Hogan, Craig J.; Jha, Saurabh; Konishi, Kohki; Lampeitl, Hubert; Marshall, Jennifer L.; McGinnis, David; Prieto, Jose Luis; Riess, Adam G.; Richmond, Michael W.; Schneider, Donald P.; Smith, Mathew; Takanashi, Naohiro; Tokita, Kouichi; van der Heyden, Kurt; Yasuda, Naoki; Zheng, Chen; Barentine, John; Brewington, Howard; Choi, Changsu; Crotts, Arlin; Dembicky, Jack; Harvanek, Michael; Im, Myunshin; Ketzeback, William; Kleinman, Scott J.; Krzesinski, Jurek; Long, Daniel C.; Malanushenko, Elena; Malanushenko, Viktor; McMillan, Russet J.; Nitta, Atsuko; Pan, Kaike; Saurage, Gabrelle; Snedden, Stephanie A.; Watters, Shannon; Wheeler, J. Craig; York, Donald; Wheeler, J. CraigItem A Multivariate Fit Luminosity Function And World Model For Long Gamma-Ray Bursts(2013-04) Shahmoradi, Amir; Shahmoradi, AmirIt is proposed that the luminosity function, the rest-frame spectral correlations, and distributions of cosmological long-duration (Type-II) gamma-ray bursts (LGRBs) may be very well described as a multivariate log-normal distribution. This result is based on careful selection, analysis, and modeling of LGRBs' temporal and spectral variables in the largest catalog of GRBs available to date: 2130 BATSE GRBs, while taking into account the detection threshold and possible selection effects. Constraints on the joint rest-frame distribution of the isotropic peak luminosity (L-iso), total isotropic emission (E-iso), the time-integrated spectral peak energy (E-p,E-z), and duration (T-90,T-z) of LGRBs are derived. The presented analysis provides evidence for a relatively large fraction of LGRBs that have been missed by the BATSE detector with E-iso extending down to similar to 10(49) erg and observed spectral peak energies (Ep) as low as similar to 5 keV. LGRBs with rest-frame duration T-90,T-z less than or similar to 1 s or observer-frame duration T-90 less than or similar to 2 s appear to be rare events (less than or similar to 0.1% chance of occurrence). The model predicts a fairly strong but highly significant correlation (rho = 0.58 +/- 0.04) between E-iso and E-p,E-z of LGRBs. Also predicted are strong correlations of L-iso and E-iso with T-90,T-z and moderate correlation between L-iso and E-p,E-z. The strength and significance of the correlations found encourage the search for underlying mechanisms, though undermine their capabilities as probes of dark energy's equation of Stateat high redshifts. The presented analysis favors-but does not necessitate-a cosmic rate for BATSE LGRBs tracing metallicity evolution consistent with a cutoff Z/Z(circle dot) similar to 0.2-0.5, assuming no luminosity-redshift evolution.Item Photometry And Spectroscopy Of GRB 060526: A Detailed Study Of The Afterglow And Host Galaxy Of A Z=3.2 Gamma-Ray Burst(2010) Thone, C. C.; Kann, D. A.; Johannesson, G.; Selj, J. H.; Jaunsen, A. O.; Fynbo, J. P. U.; Akerlof, C. W.; Baliyan, K. S.; Bartolini, C.; Bikmaev, I. F.; Bloom, J. S.; Burenin, R. A.; Cobb, B. E.; Covino, S.; Curran, P. A.; Dahle, H.; Ferrero, A.; Foley, S.; French, J.; Fruchter, A. S.; Ganesh, S.; Graham, J. F.; Greco, G.; Guarnieri, A.; Hanlon, L.; Hjorth, J.; Ibrahimov, M.; Israel, G. L.; Jakobsson, P.; Jelinek, M.; Jensen, B. L.; Jorgensen, U. G.; Khamitov, I. M.; Koch, T. S.; Levan, A. J.; Malesani, D.; Masetti, N.; Meehan, S.; Melady, G.; Nanni, D.; Naranen, J.; Pakstiene, E.; Pavlinsky, M. N.; Perley, D. A.; Piccioni, A.; Pizzichini, G.; Pozanenko, A.; Roming, P. W. A.; Rujopakarn, W.; Rumyantsev, V.; Rykoff, E. S.; Sharapov, D.; Starr, D.; Sunyaev, R. A.; Swan, H.; Tanvir, N. R.; Terra, F.; Postigo, A. D.; Vreeswijk, P. M.; Wilson, A. C.; Yost, S. A.; Yuan, F.; Wilson, A. C.Aims. With this paper we want to investigate the highly variable afterglow light curve and environment of gamma-ray burst (GRB) 060526 at z = 3.221. Methods. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the ultraviolet to the near infrared. The data set contains 412 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power law fits and with a broad-band numerical model which includes energy injections. The absorption lines detected in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526. Results. The temporal behaviour of the afterglow follows a double broken power law with breaks at t = 0.090 +/- 0.005 and t = 2.401 +/- 0.061 days. It shows deviations from the smooth set of power laws that can be modeled by additional energy injections from the central engine, although some significant microvariability remains. The broadband spectral-energy distribution of the afterglow shows no significant extinction along the line of sight. The metallicity derived from S II and Fe II of [S/H] = -0.57 +/- 0.25 and [Fe/H] = -1.09 +/- 0.24 is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. At the position of the afterglow, no host is detected to F775W(AB) = 28.5 mag with the HST, implying an absolute magnitude of the host M(1500 angstrom) > -18.3 mag which is fainter than most long-duration hosts, although the GRB may be associated with a faint galaxy at a distance of 11 kpc.