Browsing by Author "Kaviraj, Sugata"

Now showing items 1-20 of 29

    • AGN in dwarf galaxies: frequency, triggering processes and the plausibility of AGN feedback 

      Kaviraj, Sugata; Martin, Garreth; Silk, Joseph (2019-10-01)
      While active galactic nuclei (AGN) are considered to be key drivers of the evolution of massive galaxies, their potentially significant role in the dwarf-galaxy regime (M ∗ < 10 9 M ⊙) remains largely unexplored. We combine ...

    • Central Star Formation in Early-type Galaxy I Zw 81 in the Bootes Void 

      Pandey, Divya; Saha, Kanak; Pradhan, Ananta C.; Kaviraj, Sugata (2022-12-16)
      The origin of star formation in customarily passively evolving early-type massive galaxies is poorly understood. We present a case study of a massive galaxy, I Zw 81, inside the Bootes void. The void galaxy is known to ...

    • Cold-gas outflows in typical low-redshift galaxies are driven by star formation, not AGN 

      Sarzi, Marc; Kaviraj, Sugata; Nedelchev, Boris; Tiffany, Joshua; Shabala, Stanislav S.; Deller, Adam T.; Middleberg, Enno (2016-02-11)
      Energetic feedback from active galactic nuclei (AGN) is an important ingredient for regulating the star-formation history of galaxies in models of galaxy formation, which makes it important to study how AGN feedback actually ...

    • Delayed triggering of radio Active Galactic Nuclei in gas-rich minor mergers in the local Universe 

      Shabala, Stanislav; Deller, Adam; Kaviraj, Sugata; Middelberg, Enno; Turner, Ross; Ting, Yuan-Sen; Allison, James; Davis, Tim (2017-02-01)
      We examine the processes triggering star formation and Active Galactic Nucleus (AGN) activity in a sample of 25 low redshift ($z 10^7$ K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously ...

    • Eigengalaxies: describing galaxy morphology using principal components in image space 

      Uzeirbegovic, Emir; Geach, James E.; Kaviraj, Sugata (2020-09-02)
      We demonstrate how galaxy morphologies can be represented by weighted sums of "eigengalaxies" and how eigengalaxies can be used in a probabilistic framework to enable principled and simplified approaches in a variety of ...

    • Emergence and cosmic evolution of the Kennicutt-Schmidt relation driven by interstellar turbulence 

      Kraljic, Katarina; Renaud, Florent; Dubois, Yohan; Pichon, Christophe; Agertz, Oscar; Andersson, Eric; Devriendt, Julien; Freundlich, Jonathan; Kaviraj, Sugata; Kimm, Taysun; Martin, Garreth; Peirani, Sébastien; Otero, Álvaro Segovia; Volonteri, Marta; Yi, Sukyoung K. (2024-01-31)
      The scaling relations between the gas content and star formation rate of galaxies provide useful insights into the processes governing their formation and evolution. We investigated the emergence and the physical drivers ...

    • Galaxy morphological classification in deep-wide surveys via unsupervised machine learning 

      Martin, Garreth; Kaviraj, Sugata; Hocking, Alex; Read, Shaun C.; Geach, James E. (2019-10-26)
      Galaxy morphology is a fundamental quantity, that is essential not only for the full spectrum of galaxy-evolution studies, but also for a plethora of science in observational cosmology. While a rich literature exists on ...

    • Galaxy Zoo : the dependence of the star formation-stellar mass relation on spiral disk morphology 

      Willett, Kyle W.; Schawinski, Kevin; Simmons, Brooke D.; Masters, Karen L.; Skibba, Ramin A.; Kaviraj, Sugata; Melvin, Thomas; Wong, O. Ivy; Nichol, Robert C.; Cheung, Edmond; Lintott, Chris J.; Fortson, Lucy (2015-03-19)
      We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z1. Of the galaxies lying significantly above the M-SFR relation in the local Universe, more than 50% are mergers. We interpret this ...

    • Galaxy Zoo: CANDELS barred discs and bar fractions 

      Simmons, Brooke D.; Melvin, Thomas; Lintott, Chris J.; Masters, Karen L.; Willett, Kyle W.; Keel, William C.; Smethurst, R. J.; Cheung, Edmond; Nichol, Robert C.; Schawinski, Kevin; Rutkowski, Michael; Kartaltepe, Jeyhan S.; Bell, Eric F.; Casteels, Kevin R. V.; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; McIntosh, Daniel H.; Mortlock, Alice; Newman, Jeffrey A.; Ownsworth, Jamie; Bamford, Steven P.; Dahlen, Tomas; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grogin, N. A.; Grützbauch, Ruth; Guo, Yicheng; Häußler, Boris; Jek, Kian J.; Kaviraj, Sugata; Lucas, Ray A.; Peth, Michael; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn (2014-12-21)
      The formation of bars in disc galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in discs decreases from the local Universe to z ~ 1, and by z > 1 ...

    • Galaxy Zoo: major galaxy mergers are not a significant quenching pathway 

      Weigel, Anna K.; Schawinski, Kevin; Caplar, Neven; Carpineti, Alfredo; Hart, Ross E.; Kaviraj, Sugata; Keel, William C.; Kruk, Sandor J.; Lintott, Chris J.; Nichol, Robert C.; Simmons, Brooke D.; Smethurst, Rebecca J. (2017-08-21)
      We use stellar mass functions to study the properties and the significance of quenching through major galaxy mergers. In addition to SDSS DR7 and Galaxy Zoo 1 data, we use samples of visually selected major galaxy mergers ...

    • Galaxy Zoo: Quantitative Visual Morphological Classifications for 48,000 galaxies from CANDELS 

      Simmons, B. D.; Lintott, Chris; Willett, Kyle W.; Masters, Karen L.; Kartaltepe, Jeyhan S.; Häußler, Boris; Kaviraj, Sugata; Krawczyk, Coleman; Kruk, S. J.; McIntosh, Daniel H.; Smethurst, R. J.; Nichol, Robert C.; Scarlata, Claudia; Schawinski, Kevin; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; Mortlock, Alice; Newman, Jeffrey A.; Bamford, Steven P.; Grogin, N. A.; Lucas, Ray A.; Hathi, Nimish P.; McGrath, Elizabeth; Peth, Michael; Pforr, Janine; Rizer, Zachary; Wuyts, Stijn; Barro, Guillermo; Bell, Eric F.; Castellano, Marco; Dahlen, Tomas; Ownsworth, Avishai Dekel Jamie; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grützbauch, Ruth; Koo, David; Lotz, Jennifer; Mobasher, Bahram; Mozena, Mark; Salvato, Mara; Wiklind, Tommy (2017-02-01)
      We present quantified visual morphologies of approximately 48,000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified ...

    • The green valley is a red herring : Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early-and late-type galaxies 

      Schawinski, Kevin; Urry, C. Megan; Simmons, Brooke D.; Fortson, Lucy; Kaviraj, Sugata; Keel, William C.; Lintott, Chris J.; Masters, Karen L.; Nichol, Robert C.; Sarzi, Marc; Skibba, Ramin; Treister, Ezequiel; Willett, Kyle W.; Wong, O. Ivy; Yi, Sukyoung K. (2014-05-01)
      We use SDSS+GALEX+Galaxy Zoo data to study the quenching of star formation in lowredshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies ...

    • How the spectral energy distribution and galaxy morphology constrain each other, with application to morphological selection using galaxy colours 

      Uzeirbegovic, Emir; Martin, Garreth; Kaviraj, Sugata (2022-03-01)
      We introduce an empirical methodology to study how the spectral energy distribution (SED) and galaxy morphology constrain each other and implement this on 8000 galaxies from the HST CANDELS survey in the GOODS-South field. ...

    • The importance of minor-merger-driven star formation and black-hole growth in disk galaxies 

      Kaviraj, Sugata (2014-06-01)
      We use the SDSS Stripe 82 to empirically quantify the stellar-mass and black-hole growth triggered by minor mergers in local spiral (disk) galaxies. Since major mergers destroy disks and create spheroids, morphologically ...

    • An infrared study of local galaxy mergers 

      Carpineti, Alfredo; Kaviraj, Sugata; Hyde, Ashley K.; Clements, David L.; Schawinski, Kevin; Darg, Daniel; Lintott, Chris J. (2015-05-13)
      We combine a large, homogeneous sample of $\sim$3000 local mergers with the Imperial IRAS Faint Source Redshift Catalogue (IIFSCz), to perform a blind far-infrared (FIR) study of the local merger population. The IRAS-detected ...

    • Introducing the NewHorizon simulation : Galaxy properties with resolved internal dynamics across cosmic time 

      Dubois, Yohan; Beckmann, Ricarda; Bournaud, Frédéric; Choi, Hoseung; Devriendt, Julien; Jackson, Ryan; Kaviraj, Sugata; Kimm, Taysun; Kraljic, Katarina; Laigle, Clotilde; Martin, Garreth; Park, Min-Jung; Peirani, Sébastien; Pichon, Christophe; Volonteri, Marta; Yi, Sukyoung K. (2021-07-28)
      Hydrodynamical cosmological simulations are increasing their level of realism by considering more physical processes and having greater resolution or larger statistics. However, usually either the statistical power of such ...

    • Investigating the Dominant Environmental Quenching Process in UVCANDELS/COSMOS Groups 

      Kuschel, Maxwell; Scarlata, Claudia; Mehta, Vihang; Teplitz, Harry I.; Rafelski, Marc; Wang, Xin; Sunnquist, Ben; Prichard, Laura; Grogin, Norman; Koekemoer, Anton; Windhorst, Rogier; Rutkowski, Michael; Alavi, Anahita; Chartab, Nima; Conselice, Christopher J.; Dai, Y. Sophia; Gawiser, Eric; Giavalisco, Mauro; Haro, Pablo Arrabal; Hathi, Nimish; Jansen, Rolf A.; Ji, Zhiyuan; Lucas, Ray A.; Mantha, Kameswara; Mobasher, Bahram; O’Connell, Robert W.; Robertson, Brant; Sattari, Zahra; Yung, L. Y. Aaron; Davé, Romeel; DeMello, Duilia; Dickinson, Mark; Ferguson, Henry; Finkelstein, Steven L.; Hayes, Matt; Howell, Justin; Kaviraj, Sugata; Mackenty, John W.; Siana, Brian (2023-04-12)
      We explore how the fraction of quenched galaxies changes in groups of galaxies with respect to the distance to the center of the group, redshift, and stellar mass to determine the dominant process of environmental quenching ...

    • Local analogues of high-redshift star-forming galaxies: integral field spectroscopy of green peas 

      Lofthouse, Emma K.; Houghton, Ryan C. W.; Kaviraj, Sugata (2017-10-21)
      We use integral field spectroscopy, from the SWIFT and Palm3K instruments, to perform a spatially-resolved spectroscopic analysis of four nearby highly star-forming `green pea' (GP) galaxies, that are likely analogues of ...

    • Misalignment between cold gas and stellar components in early-type galaxies 

      Wong, O.I.; Schawinski, K.; Jozsa, G.I.; Urry, C.M.; Lintott, C.J.; Simmons, B.D.; Kaviraj, Sugata; Masters, K.L. (2015-03-11)
      Recent work suggests blue ellipticals form in mergers and migrate quickly from the blue cloud of star-forming galaxies to the red sequence of passively evolving galaxies, perhaps as a result of black hole feedback. Such ...

    • Molecular and atomic gas in dust lane early-type galaxies - I : Low star-formation efficiencies in minor merger remnants 

      Davis, Timothy A.; Rowlands, Kate; Allison, James R.; Shabala, Stanislav S.; Ting, Yuan-Sen; Lagos, Claudia del P.; Kaviraj, Sugata; Bourne, Nathan; Dunne, Loretta; Eales, Steve; Ivison, Rob J.; Maddox, Steve; Smith, Daniel; Smith, Matthew W. L.; Temi, Pasquale (2015-06-01)
      In this work we present IRAM-30m telescope observations of a sample of bulge-dominated galaxies with large dust lanes, which have had a recent minor merger. We find these galaxies are very gas rich, with H2 masses between ...