Browsing by Author "Kaviraj, S."

Now showing items 81-99 of 99

    • The role of minor mergers in the recent star formation history of early-type galaxies 

      Kaviraj, S.; Peirani, S.; Khochfar, S.; Silk, J.; Kay, S. (2009-04-01)
      We demonstrate that the large scatter in the ultraviolet (UV) colours of intermediate-mass early-type galaxies in the local Universe and the inferred low-level recent star formation (RSF) in these objects can be reproduced ...

    • The significant contribution of minor mergers to the cosmic star formation budget 

      Kaviraj, S. (2013-12)
      We estimate an empirical lower limit for the fraction of cosmic star formation that is triggered by minor mergers in the local Universe. Splitting the star formation budget by galaxy morphology, we find that early-type ...

    • A simple model for AGN feedback in nearby early-type galaxies 

      Kaviraj, S.; Silk, J.; Shabala, S.S.; Schawinski, K. (2011-08-01)
      Recent work (Schawinski et al.) indicates that star-forming early-type galaxies residing in the blue cloud migrate rapidly to the red sequence within around a Gyr, passing through several phases of increasingly strong ...

    • The size evolution of passive galaxies : observations from the Wide-Field Camera 3 Early Release Science program 

      Ryan Jr., R.E.; McCarthy, P.J.; Cohen, S.H.; Rutkowski, M.J.; Mechtley, M.R.; Windhorst, R.A.; Yan, H.; Hathi, N.P.; Koekemoer, A. M.; Bond, H.E.; Bushouse, H.; MacKenty, J.; Mutchler, M.; Whitmore, B.C.; O'Connell, R.W.; Balick, B.; Calzetti, D.; Crockett, R.M.; Kaviraj, S.; Silk, J.I.; Disney, M.; Dopita, M.A.; Frogel, J.A.; Hall, D.N.B.; Holtzman, J. A.; Kimble, R.A.; Paresce, F.; Saha, A.; Trauger, J.; Walker, A.R.; Young, E. (2012-04-10)
      We present the size evolution of passively evolving galaxies at z 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy ...

    • Spheroidal post-mergers in the local Universe 

      Carpineti, A.; Kaviraj, S.; Darg, D.; Lintott, C.; Shabala, S.; Schawinski, K. (2012-03-01)
      Galaxy merging is a fundamental aspect of the standard hierarchical galaxy formation paradigm. Recently, the Galaxy Zoo project has compiled a large, homogeneous catalogue of 3373 mergers, through direct visual inspection ...

    • Star formation and nuclear activity in close pairs of early-type galaxies 

      Rogers, B.; Ferreras, I.; Kaviraj, S.; Pasquali, A.; Sarzi, M. (2009-11-01)
      We extract from the Sloan Digital Sky Survey a sample of 347 systems involving early-type galaxies separated by less than 30 kpc, in projection, and 500 km s−1 in radial velocity. These close pairs are likely progenitors ...

    • The star formation histories of early-type galaxies : Insights from the rest-frame ultraviolet 

      Kaviraj, S. (2008-01-30)
      Our current understanding of the star formation histories of early-type galaxies is reviewed, in the context of recent observational studies of their ultraviolet (UV) properties. Combination of UV and optical spectro-photometric ...

    • Strategies for optimal sky subtraction in the low surface brightness regime 

      Watkins, A. E.; Kaviraj, S.; Collins, C. C.; Knapen, J. H.; Kelvin, L. S.; Duc, P. -A.; Román, J.; Mihos, J. C. (2024-03-01)
      The low surface brightness (LSB) regime (μg  ≳  26 mag arcsec−2) comprises a vast, mostly unexplored discovery space, from dwarf galaxies to the diffuse interstellar medium. Accessing this regime requires precisely removing ...

    • The sudden death of the nearest quasar 

      Schawinski, K.; Virani, S.; Urry, C.M.; Natarajan, P.; Coppi, P.; Evans, D.A.; Keel, W.C.; Manning, A.; Lintott, C.J.; Kaviraj, S.; Bamford, S.P.; Józsa, G.I.G.; Garrett, M.; Van Arkel, H.; Gay, P.; Fortson, L. (2010-11-20)
      Galaxy formation is significantly modulated by energy output from supermassive black holes at the centers of galaxies which grow in highly efficient luminous quasar phases. The timescale on which black holes transition ...

    • Suppression of star formation in early-type galaxies by feedback from supermassive black holes 

      Schawinski, K.; Khochfar, S.; Kaviraj, S.; Yi, S.K.; Lee, Y.-W.; Boselli, A.; Donas, J.; Milliard, B.; Barlow, T.; Conrow, T.; Forster, K.; Friedman, P.G.; Martin, D.C.; Morrissey, P.; Seibert, M.; Small, T.; Wyder, T.K.; Neff, S.; Schiminovich, D.; Bianchi, L.; Heckman, T.; Szalay, A.; Madore, B.; Rich, R.M. (2006-08-24)
      Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in ...

    • Tidal dwarf galaxies in the nearby Universe 

      Kaviraj, S.; Darg, D.; Lintott, C.; Silk, J.; Schawinski, K. (2012-01-01)
      We present a statistical observational study of the tidal dwarf (TD) population in the nearby Universe by exploiting a large, homogeneous catalogue of galaxy mergers compiled from the Sloan Digital Sky Survey. 95percent ...

    • Transfer learning for galaxy morphology from one survey to another 

      Sánchez, H. Domínguez; Huertas-Company, M.; Bernardi, M.; Kaviraj, S.; Fischer, J. L.; Abbott, T. M. C.; Abdalla, F. B.; Annis, J.; Avila, S.; Buckley-Geer, E.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; Costa, L. N. da; Davis, C.; Vicente, J. De; Doel, P.; Evrard, A. E.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hartley, W. G.; Hollowood, D. L.; Honscheid, K.; Hoyle, B.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Melchior, P.; Menanteau, F.; Miquel, R.; Nord, B.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.; Zuntz, J. (2018-12-28)
      Deep Learning (DL) algorithms for morphological classification of galaxies have proven very successful, mimicking (or even improving) visual classifications. However, these algorithms rely on large training samples of ...

    • Triggered star formation in the inner filament of Centaurus A 

      Crockett, R.M.; Shabala, S.S.; Kaviraj, S.; Silk, J.; Antonuccio-Delogu, V.; Mutchler, M.; Whitmore, B.C.; O'Connell, R.W.; Rejkuba, M.; Windhorst, R.A. (2012-04-01)
      We present recent Hubble Space Telescope observations of the inner filament of Centaurus A, using the new Wide Field Camera 3 (WFC3) F225W, F657N and F814W filters. We find a young stellar population near the south-west ...

    • An ultraviolet study of nearby luminous infrared galaxies : Star formation histories and the role of AGN 

      Kaviraj, S. (2009-04-01)
      We employ ultraviolet (UV) and optical photometry, from the Galaxy Evolution Explorer (GALEX) and Sloan Digital Sky Survey (SDSS) surveys, respectively, to study the star formation histories (SFHs) of 561 luminous infrared ...

    • UV bright globular clusters in M87 : More evidence for super-He-rich stellar populations? 

      Kaviraj, S.; Sohn, S.T.; O'Connell, R.W.; Yoon, S.-J.; Lee, Y.W.; Yi, S.K. (2007-05-01)
      We study the ultraviolet (UV) and optical properties of 38 massive globular clusters (GCs) in the Virgo elliptical, M87, imaged using the STIS and WFPC2 instruments onboard the Hubble Space Telescope. The majority of these ...

    • The UV colours of high-redshift early-type galaxies : Evidence for recent star formation and stellar mass assembly over the last 8 billion years 

      Kaviraj, S.; Khochfar, S.; Schawinski, K.; Silk, J.; Yi, S.K.; Gawiser, E.; Virani, S.N.; Cardamone, C.N.; van Dokkum, P.G.; Urry, C.M. (2008-07)
      We combine deep optical and NIR (UBVRIzJK) photometry from the Multiwavelength Survey by Yale-Chile (MUSYC) with redshifts from the COMBO-17 survey to perform a large-scale study of the rest-frame ultraviolet (UV) properties ...

    • The UV properties of E+A galaxies : Constraints on feedback-driven quenching of star formation 

      Kaviraj, S.; Kirkby, L.A.; Silk, J.; Sarzi, M. (2007-12-01)
      We present the first large-scale study of E+A galaxies that incorporates photometry in the ultraviolet (UV) wavelengths. E+A galaxies are 'post-starburst' systems, with strong Balmer absorption lines indicating significant ...

    • UV-optical colors as probes of early-type galaxy evolution 

      Kaviraj, S.; Schawinski, K.; Devriendt, J.E.G.; Ferreras, I.; Khochfar, S.; Yoon, S.-J.; Yi, S.K.; Lee, Y.-W.; Deharveng, J.-M.; Boselli, A.; Donas, J.; Milliard, B.; Barlow, T.; Conrow, T.; Forster, K.; Friedman, P.G.; Martin, D.C.; Morrissey, P.; Seibert, M.; Small, T.; Wyder, T.; Neff, S.; Schiminovich, D.; Bianchi, L.; Heckman, T.; Szalay, A.; Madore, B.; Rich, R.M. (2007-12-01)
      We have studied ∼2100 early-type galaxies in the SDSS DR3 which have been detected by the GALEX Medium Imaging Survey (MIS), in the redshift range O <z <0.1.1. Combining GALEXUV photometry with corollary optical data from ...

    • A WFC3 study of globular clusters in NGC 4150 : An early-type minor merger 

      Kaviraj, S.; Mark Crockett, R.; Silk, J.; Whitmore, B.C.; Mutchler, M.; O'Connell, R.W.; Windhorst, R.A.; Rejkuba, M.; Yi, S.; Frogel, J.A.; Calzetti, D. (2012-05-01)
      We combine near-ultraviolet (NUV; 2250 Å) and optical (U, B, V, I) imaging from the Wide Field Camera 3 (WFC3), on-board the Hubble Space Telescope (HST), to study the globular cluster (GC) population in NGC 4150, a sub-L* ...