Browsing by Author "Kaviraj, S."

Now showing items 21-40 of 99

    • Effects of large-scale AGN feedback in local galaxies 

      Shabala, S.; Kaviraj, S.; Silk, J. (2012-08)
      The effects of active galactic nucleus (AGN) feedback on group and cluster galaxies are investigated. We examine the colors of non-AGN hosts (i.e. satellite galaxies) by comparing galaxies overrun by radio AGN with similar ...

    • The elliptical galaxy colour-magnitude relation as a discriminant between the monolithic and merger paradigms 

      Kaviraj, S.; Devriendt, J.E.G.; Ferreras, I.; Yi, S.K. (2005-06-11)
      The colour-magnitude relation (CMR) of cluster elliptical galaxies has been widely used to constrain their star formation histories (SFHs) and to discriminate between the monolithic collapse and merger paradigms of elliptical ...

    • Enhancement of critical current density of (Pb,Sn)-doped Bi-2212 superconductors at high temperature 

      Li, Y.; Kaviraj, S.; Berenov, A.; Perkins, G.K.; Driscoll, J.; Caplin, A.D.; Cao, G.H.; Ma, Q.Z.; Wang, B.; Wei, L.; Zhao, Z.X. (2001-06)
      The magnetic properties of ceramic samples of Bi(PbSn)SrCaCu O (x = 0,0.1,0.2,0.3 and 0.4) superconductors have been investigated using a vibrating sample magnetometer from 20 to 50 K and up to 8 T. Phase analysis shows ...

    • Environment and the epochs of galaxy formation in the SDSS era 

      Thomas, D.; Maraston, C.; Schawinski, K.; Joo, S.-J.; Kaviraj, S.; Sarzi, M.; Yi, S.K. (2006-12-01)
      We analyse a sample of 1,652 elliptical galaxies morphologically selected from the SDSS DR4 with respect to their stellar population properties such as luminosity weighted ages, metallicities and /Fe element abundance ...

    • Evidence for recent star formation in BCGs : A correspondence between blue cores and UV excess 

      Pipino, A.; Kaviraj, S.; Silk, J.; Bildfell, C.; Babul, A.; Hoekstra, H. (2009-05-01)
      We present a joint analysis of near-ultraviolet (NUV) data from the GALEX (Galaxy Evolution Explorer) mission and (optical) colour profiles for a sample of seven brightest cluster galaxies (BCGs) in the Canadian Cluster ...

    • Exploring the formation of spheroidal galaxies out to z ∼ 1.5 in GOODS 

      Ferreras, I.; Lisker, T.; Pasquali, A.; Kaviraj, S. (2009-05-01)
      The formation of massive spheroidal galaxies is studied on a visually classified sample extracted from the Advanced Camera for Surveys/Hubble Space Telescope (ACS/HST) images of the Great Observatories Origins Deep Survey ...

    • Extremely massive disc galaxies in the nearby Universe form through gas-rich minor mergers 

      Jackson, R. A.; Kaviraj, S.; Martin, G.; Devriendt, J. E. G.; Noakes-Kettel, E. A.; Silk, J.; Ogle, P.; Dubois, Y. (2022-01-14)
      In our hierarchical structure-formation paradigm, the observed morphological evolution of massive galaxies -- from rotationally-supported discs to dispersion-dominated spheroids -- is largely explained via galaxy merging. ...

    • The formation and evolution of low-surface-brightness galaxies 

      Martin, G.; Kaviraj, S.; Laigle, C.; Devriendt, J. E. G.; Jackson, R. A.; Peirani, S.; Dubois, Y.; Pichon, C.; Slyz, A. (2019-05-01)
      Our statistical understanding of galaxy evolution is fundamentally driven by objects that lie above the surface-brightness limits of current wide-area surveys (μ ∼23 mag arcsec -2). While both theory and small, deep surveys ...

    • The formation of cores in galaxies across cosmic time - the existence of cores is not in tension with the ΛCDM paradigm 

      Jackson, R. A.; Kaviraj, S.; Yi, S. K.; Peirani, S.; Dubois, Y.; Martin, G.; Devriendt, J. E. G.; Slyz, A.; Pichon, C.; Volonteri, M.; Kimm, T.; Kraljic, K. (2024-02-01)
      The 'core-cusp' problem is considered a key challenge to the ΛCDM paradigm. Haloes in dark matter only simulations exhibit 'cuspy' profiles, where density continuously increases towards the centre. However, the dark matter ...

    • Galaxy evolution explorer ultraviolet color-magnitude relations and evidence of recent star formation in early-type galaxies 

      Yi, S.K.; Yoon, S.-J.; Lee, Y.-W.; Ree, C.H.; Sohn, Y.-J.; Rey, S.-C.; Rhee, J.; Byun, Y.-I.; Kim, S.-W.; Kaviraj, S.; Deharveng, J.-M.; Boselli, A.; Donas, J.; Malina, R.; Milliard, B.; Rich, R.M.; Salim, S.; Friedman, P.G.; Martin, D.C.; Morrissey, P.; Small, T.; Barlow, T.; Forster, K.; Wyder, T.K.; Lee, J.-W.; Bianchi, L.; Heckman, T.M.; Szalay, A.S.; Jee, M.J.; Jelinsky, P.; Siegmund, O.; Welsh, B.; Madore, B.F.; Neff, S.; Schiminovich, D. (2005-01-20)
      We have used the Galaxy Evolution Explorer UV photometric data to construct a first near-UV (NUV) color-magnitude relation (CMR) for the galaxies preclassified as early-type by Sloan Digital Sky Survey studies. The NUV CMR ...

    • Galaxy merger histories and the role of merging in driving star formation at z>1 

      Kaviraj, S.; Devriendt, J.; Dubois, Y.; Slyz, A.; Welker, C.; Pichon, C.; Peirani, S.; Borgne, D. Le (2015-09-21)
      We use Horizon-AGN, a hydrodynamical cosmological simulation, to explore the role of mergers in the evolution of massive (M > 10^10 MSun) galaxies around the epoch of peak cosmic star formation (1zR(4:1 3 are 'blue' (i.e. ...

    • Galaxy zoo 2 : Detailed morphological classifications for 304,122 galaxies from the sloan digital sky survey 

      Willett, K.W.; Lintott, C.J.; Bamford, S.P.; Masters, K.L.; Simmons, B.D.; Casteels, K.R.V.; Edmondson, E.M.; Fortson, L.F.; Kaviraj, S.; Keel, W.C.; Melvin, T.; Nichol, R.C.; Jordan Raddick, M.; Schawinski, K.; Simpson, R.J.; Skibba, R.A.; Smith, A.M.; Thomas, D. (2013-11-01)
      We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304,122 galaxies drawn from the Sloan Digital Sky Survey (SDSS).Morphology is a ...

    • Galaxy Zoo : Building the low-mass end of the red sequence with local post-starburst galaxies 

      Wong, O.I.; Schawinski, K.; Kaviraj, S.; Lintott, C.; Darg, D.; Masters, K.L.; Nichol, R.C.; Thomas, D.; Keel, W.C.; Bamford, S.P.; Andreescu, D.; Murray, P.; Raddick, M.J.; Szalay, A.; Vandenberg, J. (2012-02-01)
      We present a study of local post-starburst galaxies (PSGs) using the photometric and spectroscopic observations from the Sloan Digital Sky Survey and the results from the Galaxy Zoo project. We find that the majority of ...

    • Galaxy Zoo : Dust and molecular gas in early-type galaxies with prominent dust lanes 

      Kaviraj, S.; Ting, Y. S.; Bureau, M.; Shabala, S.S.; Crockett, R.M.; Silk, J.; Lintott, C.; Smith, A.; Keel, W.C.; Masters, K.L.; Schawinski, K.; Bamford, S.P. (2012-06-01)
      We explore the properties of dust and associated molecular gas in 352 nearby (0.01 <z <0.07) early-type galaxies (ETGs) with prominent dust lanes, drawn from the Sloan Digital Sky Survey (SDSS). Two-thirds of these 'dusty ...

    • Galaxy Zoo : Dust lane early-type galaxies are tracers of recent, gas-rich minor mergers 

      Shabala, S.S.; Ting, Y. S.; Kaviraj, S.; Lintott, C.; Crockett, R.M.; Silk, J.; Sarzi, M.; Schawinski, K.; Bamford, S.P.; Edmondson, E. (2012-06-01)
      We present the second of two papers concerning the origin and evolution of local early-type galaxies exhibiting dust features. We use optical and radio data to examine the nature of active galactic nucleus (AGN) activity ...

    • Galaxy zoo : The fundamentally different co-evolution of supermassive black holes and their early- and late-type host galaxies 

      Schawinski, K.; Urry, C.M.; Virani, S.; Coppi, P.; Cardamone, C.N.; Bamford, S.P.; Treister, E.; Lintott, C.J.; Kaviraj, S.; Sarzi, M.; Keel, W.C.; Masters, K.L.; Nichol, R.C.; Thomas, D.; Ross, N.P.; Andreescu, D.; Murray, P.; Raddick, M.J.; Szalay, A.S.; Vandenberg, J.; Slosar, A. (2010-01-01)
      We use data from the Sloan Digital Sky Survey and visual classifications of morphology from the Galaxy Zoo project to study black hole growth in the nearby universe (z <0.05) and to break down the active galactic nucleus ...

    • Galaxy Zoo: a sample of blue early-type galaxies at low redshift 

      Schawinski, K.; Lintott, C.; Kaviraj, S.; Khochfar, S.; Land, K.; Thomas, D.; Bamford, S. P.; Nichol, R.C.; Sarzi, M.; Andreescu, D.; Murray, P.; Raddick, M.J.; Szalay, A.; Vandenberg, J.; Slosar, A.; Yi, S.K. (2009)
      We report the discovery of a population of nearby, blue early-type galaxies with high star formation rates (0.5 < SFR < 50 M⊙ yr−1) . They are identified by their visual morphology as provided by Galaxy Zoo for Sloan Digital ...

    • Galaxy Zoo: Bulgeless galaxies with growing black holes 

      Simmons, B.; Lintott, C.; Kaviraj, S.; Schawinski, K.; Han, A.; Urry, C.M.; Moran, E.C.; Masters, K.L.; Nichol, R.C.; Willett, K.W.; Bamford, S.P. (2013-03)
      The growth of supermassive black holes appears to be driven by galaxy mergers, violent merger-free processes and/or 'secular' processes. In order to quantify the effects of secular evolution on black hole growth, we study ...

    • Galaxy Zoo: evidence for Diverse Star Formation Histories through the Green Valley 

      Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Marshall, P. J.; Bamford, S.; Fortson, L.; Kaviraj, S.; Masters, K. L.; Melvin, T.; Nichol, R. C.; Skibba, R. A.; Willett, K. W. (2015-04-17)
      Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary pathways between early- and late-type galaxies, ...

    • Galaxy Zoo: Multimergers and the Millennium Simulation 

      Darg, D.W.; Kaviraj, S.; Lintott, C.J.; Silk, J.; Lynn, S.; Schawinski, K.; Bamford, S.; Nichol, R.C. (2011-09)
      We present a catalogue of 39 multiple mergers, found using the mergers catalogue of the Galaxy Zoo project for z <0.1, and compare them to corresponding semi-analytical galaxies from the Millennium Simulation. We estimate ...