Browsing by Subject "physical properties"

Now showing 1 - 5 of 5
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    OPTICAL DISCOVERY OF PROBABLE STELLAR TIDAL DISRUPTION FLARES
    (2011) van Velzen, Sjoert; Farrar, Glennys R; Gezari, Suvi; Morrell, Nidia; Zaritsky, Dennis; Östman, Linda; Smith, Mathew; Gelfand, Joseph; Drake, Andrew J
    Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures of 2 Multiplication-Sign 10{sup 4} K and observed peak luminosities of M{sub g} = -18.3 and -20.4 ({nu}L{sub {nu}} = 5 Multiplication-Sign 10{sup 42}, 4 Multiplication-Sign 10{sup 43} erg s{sup -1}, in the rest frame); their cooling rates are very low, qualitatively consistent with expectations for tidal disruption flares. The properties of the TDE candidates are examined using (1) SDSS imaging to compare them to other flares observed in the search, (2) UV emission measured by GALEX, and (3) spectra of the hosts and of one of the flares. Our pipeline excludes optically identifiable AGN hosts, and our variability monitoring over nine years provides strong evidence that these are not flares in hidden AGNs. The spectra and color evolution of the flares are unlike any SN observed to date, their strong late-time UV emission is particularly distinctive, and they are nuclear at high resolution arguing against these being first cases of a previously unobserved class of SNemore » or more extreme examples of known SN types. Taken together, the observed properties are difficult to reconcile with an SN or an AGN-flare explanation, although an entirely new process specific to the inner few hundred parsecs of non-active galaxies cannot be excluded. Based on our observed rate, we infer that hundreds or thousands of TDEs will be present in current and next-generation optical synoptic surveys. Using the approach outlined here, a TDE candidate sample with O(1) purity can be selected using geometric resolution and host and flare color alone, demonstrating that a campaign to create a large sample of TDEs, with immediate and detailed multi-wavelength follow-up, is feasible. A by-product of this work is quantification of the power spectrum of extreme flares in AGNs.« less
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    PHOTOMETRIC ESTIMATES OF REDSHIFTS AND DISTANCE MODULI FOR TYPE Ia SUPERNOVAE
    (2010) Kessler, Richard; Cinabro, David; Bassett, Bruce; Dilday, Benjamin; Frieman, Joshua A; Garnavich, Peter M; Jha, Saurabh; Marriner, John; Nichol, Robert C; Sako, Masao; Smith, Mathew; Bernstein, Joseph P; Bizyaev, Dmitry; Goobar, Ariel; Kuhlmann, Stephen; Schneider, Donald P; Stritzinger, Maximilian
    Large planned photometric surveys will discover hundreds of thousands of supernovae (SNe), outstripping the resources available for spectroscopic follow-up and necessitating the development of pure ...
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    The effect of peculiar velocities on supernova cosmology
    (2011) Davis, Tamara M; Hui, Lam; Frieman, Joshua A; Haugbølle, Troels; Kessler, Richard; Sinclair, Benjamin; Sollerman, Jesper; Bassett, Bruce; Marriner, John; Mörtsell, Edvard; Nichol, Robert C; Richmond, Michael W; Sako, Masao; Schneider, Donald P; Smith, Mathew
    We analyze the effect that peculiar velocities have on the cosmological inferences we make using luminosity distance indicators, such as Type Ia supernovae. In particular we study the corrections r ...
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    Thick disks of edge-on galaxies seen through the spitzer survey of stellar structure in galaxies (s 4 g): lair of missing baryons?
    (2011) Comerón, Sébastien; Elmegreen, Bruce G; Knapen, Johan H; Salo, Heikki; Laurikainen, Eija; Laine, Jarkko; Athanassoula, E; Bosma, Albert; Sheth, Kartik; Regan, Michael W; Hinz, Joannah L; de Paz, Armando Gil; Menéndez-Delmestre, Karín; Mizusawa, Trisha; Muñoz-Mateos, Juan-Carlos; Seibert, Mark; Kim, Taehyun; Elmegreen, Debra M; Gadotti, Dimitri A; Ho, Luis C; Holwerda, Benne W; Lappalainen, Jani; Schinnerer, Eva; Skibba, Ramin
    Most, if not all, disk galaxies have a thin (classical) disk and a thick disk. In most models thick disks are thought to be a necessary consequence of the disk formation and/or evolution of the galaxy. We present the results of a study of the thick disk properties in a sample of carefully selected edge-on galaxies with types ranging from T = 3 to T = 8. We fitted one-dimensional luminosity profiles with physically motivated functions-the solutions of two stellar and one gaseous isothermal coupled disks in equilibrium-which are likely to yield more accurate results than other functions used in previous studies. The images used for the fits come from the Spitzer Survey of Stellar Structure in Galaxies (S(4)G). We found that thick disks are on average more massive than previously reported, mostly due to the selected fitting function. Typically, the thin and thick disks have similar masses. We also found that thick disks do not flare significantly within the observed range in galactocentric radii and that the ratio of thick-to-thin disk scale heights is higher for galaxies of earlier types. Our results tend to favor an in situ origin for most of the stars in the thick disk. In addition, the thick disk may contain a significant amount of stars coming from satellites accreted after the initial buildup of the galaxy and an extra fraction of stars coming from the secular heating of the thin disk by its own overdensities. Assigning thick disk light to the thin disk component may lead to an underestimate of the overall stellar mass in galaxies because of different mass-to-light ratios in the two disk components. On the basis of our new results, we estimate that disk stellar masses are between 10% and 50% higher than previously thought and we suggest that thick disks are a reservoir of “local missing baryons.”
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    Type II-P supernovae from the SDSS-II supernova survey and the standardized candle method
    (2010) D’Andrea, Chris B; Sako, Masao; Dilday, Benjamin; Frieman, Joshua A; Holtzman, Jon; Kessler, Richard; Konishi, Kohki; Schneider, D P; Sollerman, Jesper; Wheeler, J Craig; Yasuda, Naoki; Cinabro, David; Jha, Saurabh; Nichol, Robert C; Lampeitl, Hubert; Smith, Mathew; Atlee, David W; Bassett, Bruce; Castander, Francisco J; Goobar, Ariel; Miquel, Ramon; Nordin, Jakob; Östman, Linda; Prieto, José L; Quimby, Robert; Riess, Adam G; Stritzinger, Maximilian
    We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discov ...