Browsing by Author "Freedman, W"

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    The stellar content of the bulge of M31
    (2003) Stephens, AW; Frogel, JA; DePoy, DL; Freedman, W; Gallart, C; Jablonka, P; Renzini, A; Rich, RM; Davies, R
    We analyze the stellar populations present in M31 by using nine sets of adjacent Hubble Space Telescope NICMOS camera 1 and 2 fields with galactocentric distances ranging from 2' to 20'. These infrared observations provide some of the highest spatial resolution measurements of M31 to date; our data place tight constraints on the maximum luminosities of stars in the bulge of M31. The tip of the red giant branch is clearly visible at M-bol similar to -3.8, and the tip of the asymptotic giant branch (AGB) extends to M-bol similar to -5. This AGB peak luminosity is significantly fainter than previously claimed; through direct comparisons and simulations we show that previous measurements were affected by image blending. We do observe field-to-field variations in the luminosity functions, but simulations show that these differences can be produced by blending in the higher surface brightness fields. We conclude that the red giant branch of the bulge of M31 is not measurably different from that of the bulge of the Milky Way. We also find an unusually high number of bright bluish stars (7.3 arcmin(-2)), which appear to be Galactic foreground stars.
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    The Type Ia supernova 1999aw
    (2002) Strolger, LG; Smith, RC; Suntzeff, NB; Phillips, MM; Aldering, G; Nugent, P; Knop, R; Perlmutter, S; Schommer, RA; Ho, LC; Hamuy, M; Krisciunas, K; Germany, LM; Covarrubias, R; Candia, P; Athey, A; Blanc, G; Bonacic, A; Bowers, T; Conley, A; Dahlén, T; Freedman, W; Galaz, G; Gates, E; Goldhaber, G; Goobar, A; Groom, D; Hook, IM; Marzke, R; Mateo, M; McCarthy, P; Méndez, J; Muena, C; Persson, SE; Quimby, R; Roth, M; Ruiz-Lapuente, P; Seguel, J; Szentgyorgyi, A; von Braun, K; Wood-Vasey, WM; York, T
    SN 1999aw was discovered during the first campaign of the Nearby Galaxies Supernova Search project. This luminous, slow-declining [Deltam(15)(B) = 0.81 +/- 0.03] Type Ia supernova was noteworthy in at least two respects. First, it occurred in an extremely low luminosity host galaxy that was not visible in the template images nor in initial subsequent deep imaging. Second, the photometric and spectral properties of this supernova indicate that it very likely was similar to the subclass of Type Ia supernovae whose prototype is SN 1999aa. This paper presents the BVRI and J(s)HK(s) light curves of SN 1999aw ( through similar to100 days past maximum light), as well as several epochs of optical spectra. From these data, we calculate the bolometric light curve and give estimates of the luminosity at maximum light and the initial Ni-56 mass. In addition, we present deep BVI images obtained recently with the Baade 6.5 m telescope at Las Campanas Observatory that reveal the remarkably low-luminosity host galaxy.