Browsing by Subject "red shift"

Now showing 1 - 9 of 9
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    Evidence for a clumpy, rotating gas disk in a submillimeter galaxy at z = 4
    (2012) Hodge, J A; Carilli, C L; Walter, F; de Blok, W J G; Riechers, D; Daddi, E; Lentati, L
    We present Karl G. Jansky Very Large Array observations of the CO(2-1) emission in the z = 4.05 submillimeter galaxy (SMG) GN20. These high-resolution data allow us to image the molecular gas at 1.3 kpc resolution just 1.6 Gyr after the big bang. The data reveal a clumpy, extended gas reservoir, 14 {+-} 4 kpc in diameter, in unprecedented detail. A dynamical analysis shows that the data are consistent with a rotating disk of total dynamical mass 5.4 {+-} 2.4 Multiplication-Sign 10{sup 11} M {sub Sun }. We use this dynamical mass estimate to constrain the CO-to-H{sub 2} mass conversion factor ({alpha}{sub CO}), finding {alpha}{sub CO} = 1.1 {+-} 0.6 M {sub Sun }(K km s{sup -1} pc{sup 2}){sup -1}. We identify five distinct molecular gas clumps in the disk of GN20 with masses a few percent of the total gas mass, brightness temperatures of 16-31K, and surface densities of >3200-4500 Multiplication-Sign ({alpha}{sub CO}/0.8) M {sub Sun} pc{sup -2}. Virial mass estimates indicate they could be self-gravitating, and we constrain their CO-to-H{sub 2} mass conversion factor to be <0.2-0.7 M {sub Sun }(K km s{sup -1} pc{sup 2}){sup -1}. A multiwavelength comparison demonstrates that the molecular gas is concentrated in a region of the galaxy that is heavily obscured in the rest-frame UV/optical. We investigate the spatially resolved gas excitation and find that the CO(6-5)/CO(2-1) ratio is constant with radius, consistent with star formation occurring over a large portion of the disk. We discuss the implications of our results in the context of different fueling scenarios for SMGs.
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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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    PHOTOMETRIC TYPE Ia SUPERNOVA CANDIDATES FROM THE THREE-YEAR SDSS-II SN SURVEY DATA
    (2011) Sako, Masao; Bassett, Bruce; Connolly, Brian; Dilday, Benjamin; Cambell, Heather; Frieman, Joshua A; Gladney, Larry; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Nichol, Robert C; Schneider, Donald P; Smith, Mathew; Sollerman, Jesper
    We analyze the three-year Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey data and identify a sample of 1070 photometric Type Ia supernova (SN Ia) candidates based on their multiband li ...
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    Spectroscopic properties of star-forming host galaxies and type Ia supernova hubble residuals in a nearly unbiased sample
    (2011) D\'Andrea, Chris B; Gupta, Ravi R; Sako, Masao; Morris, Matt; Nichol, Robert C; Brown, Peter J; Campbell, Heather; Olmstead, Matthew D; Frieman, Joshua A; Garnavich, Peter; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Schneider, Donald P; Smith, Mathew
    We examine the correlation between supernova (SN) host-galaxy properties and their residuals in the Hubble diagram. We use SNe discovered during the Sloan Digital Sky Survey-II Supernova Survey, and focus on objects at a redshift of z < 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova (SN Ia) sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23 < M{sub r} < -17. In contrast to previous works that use photometric estimates of host mass as a proxy for global metallicity, we analyze host-galaxy spectra to obtain gas-phase metallicities and star formation rates (SFRs) from host galaxies with active star formation. From a final sample of {approx}40 emission-line galaxies, we find that light-curve-corrected SNe Ia are {approx}0.1 mag brighter in high-metallicity hosts than in low-metallicity hosts. We also find a significant (>3{sigma}) correlation between the Hubble Residuals of SNe Ia and the specific SFR of the host galaxy. We comment on the importance of SN/host-galaxy correlations as a source of systematic bias in future deep SN surveys.
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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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    THE EFFECT OF WEAK LENSING ON DISTANCE ESTIMATES FROM SUPERNOVAE
    (2014) Smith, Mathew; Bacon, David J; Nichol, Robert C; Campbell, Heather; Clarkson, Chris; Maartens, Roy; D\'Andrea, Chris B; Bassett, Bruce A; Cinabro, David; Finley, David A; Frieman, Joshua A; Galbany, Lluís; Garnavich, Peter M; Olmstead, Matthew D; Schneider, Donald P; Shapiro, Charles; Sollerman, Jesper
    Using a sample of 608 Type Ia supernovae from the SDSS-II and BOSS surveys, combined with a sample of foreground galaxies from SDSS-II, we estimate the weak lensing convergence for each supernova l ...
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    The impact of the gas distribution on the determination of dynamical masses of galaxies using unresolved observations
    (2014) de Blok, W J G; Walter, Fabian
    Dynamical mass (M dyn) is a key property of any galaxy, yet a determination of M dyn is not straightforward if spatially resolved measurements are not available. This situation occurs in single-dish H I observations of the local universe, but also frequently in high-redshift observations. M dyn measurements in high-redshift galaxies are commonly obtained through observations of the CO line, the most abundant tracer of the molecular medium. Even though in most cases the CO line width can be determined with reasonable accuracy, a measurement of the size of the emitting region is typically challenging given current facilities. We show how the integrated spectra ("global profiles") of a variety of galaxy models depend on the spatial distribution of the tracer gas as well as its velocity dispersion. We demonstrate that the choice of tracer emission line (e.g., H I tracing extended, "flat," emission versus CO tracing more compact, "exponential," emission) significantly affects the shape of the global profiles. In particular, in the case of high (~50 km s–1) velocity dispersions, compact tracers (such as CO) result in Gaussian-like (non-double-horned) profiles, as is indeed frequently seen in high-redshift observations. This leads to significantly different determinations of M dyn if different distributions of the tracer material ("flat" versus "exponential") are considered. We determine at which radii the rotation curve reaches the rotation velocity corresponding to the velocity width, and find that for each tracer this happens at a well-defined radius: H I velocity widths typically originate at ~5 optical scale lengths, while CO velocity widths trace the rotation velocity at ~2 scale lengths. We additionally explore other distributions to take into account that CO distributions at high redshift likely differ from those at low redshift. Our models, while not trying to reproduce individual galaxies, define characteristic radii that can be used in conjunction with the measured velocity widths in order to define dynamical masses consistent with the assumed gas distribution.
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    THE SDSS-II SUPERNOVA SURVEY: PARAMETERIZING THE TYPE Ia SUPERNOVA RATE AS A FUNCTION OF HOST GALAXY PROPERTIES
    (2012) Smith, Mathew; Nichol, Robert C; Dilday, Benjamin; Marriner, John; Kessler, Richard; Bassett, Bruce; Cinabro, David; Frieman, Joshua; Garnavich, Peter; Jha, Saurabh W; Lampeitl, Hubert; Sako, Masao; Schneider, Donald P; Sollerman, Jesper
    Using data from the Sloan Digital Sky Supernova Survey-II (SDSS-II SN Survey), we measure the rate of Type Ia supernovae (SNe Ia) as a function of galaxy properties at intermediate redshift. A samp ...
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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 ...