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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Dr Aprajita Verma

Senior Research Fellow

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Zooniverse
  • Astronomical instrumentation
  • Galaxy formation and evolution
  • Rubin-LSST
  • Extremely Large Telescope
aprajita.verma@physics.ox.ac.uk
Telephone: 01865 (2)73374
Denys Wilkinson Building, room 760
  • About
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  • Publications

Lyman-break galaxies at z~5 -I. First significant stellar mass assembly in galaxies that are not simply z~3 LBGs at higher redshift

(2007)

Authors:

Aprajita Verma, Matthew D Lehnert, Natascha M Foerster Schreiber, Malcolm N Bremer, Laura Douglas
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Lyman-break galaxies at z ∼ 5 - I. First significant stellar mass assembly in galaxies that are not simply z ∼ 3 LBGs at higher redshift

Monthly Notices of the Royal Astronomical Society 377:3 (2007) 1024-1042

Authors:

A Verma, MD Lehnert, NM Förster Schreiber, MN Bremer, L Douglas

Abstract:

We determine the ensemble properties of Lyman-break galaxies (LBGs) selected as V-band dropouts to in the Chandra Deep Field-South using their rest-frame UV-to-visible spectral energy distributions. By matching the selection and performing the same analysis that has been used for samples, we show clear differences in the ensemble properties of two samples of LBGs which are separated by 1 Gyr in look-back time. We find that LBGs are typically much younger (<100 Myr) and have lower stellar masses than their counterparts (which are typically ∼ few × and ∼320 Myr old). The difference in mass is significant even when considering the presence of an older, underlying population in both samples. Such young and moderately massive systems dominate the luminous LBG population (≳70 per cent), whereas they comprise ≲30 per cent of LBG samples at. This result, which we demonstrate is robust under all reasonable modelling assumptions, shows a clear change in the properties of the luminous LBGs between and. These young and moderately massive LBGs appear to be experiencing their first (few) generations of large-scale star formation and are accumulating their first significant stellar mass. Their dominance in luminous LBG samples suggests that witnesses a period of wide-spread, recent galaxy formation. As such, LBGs are the likely progenitors of the spheroidal components of present-day massive galaxies. This is supported by their high stellar mass surface densities, and is consistent with their core phase-space densities, as well as the ages of stars in the bulge of our Galaxy and other massive systems. With implied formation redshifts of, these luminous LBGs could have only contributed to the UV photon budget at the end of reionization. However, their high star formation rates per unit area suggest these systems host outflows or winds that enrich the intragalactic and intergalactic media with metals, as has been established for LBGs. Their estimated young ages are consistent with inefficient metal-mixing on galaxy-wide scales. Therefore these galaxies may contain a significant fraction of Population III stars as proposed for LBGs by Jiminez & Haimann. © 2007 The Authors. Journal compilation © 2007 RAS.
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The discovery of a massive supercluster at z = 0.9 in the UKIDSS deep eXtragalactic survey

Monthly Notices of the Royal Astronomical Society 379:4 (2007) 1343-1351

Authors:

AM Swinbank, AC Edge, I Smail, JP Stott, M Bremer, Y Sato, C Van Breukelen, M Jarvis, I Waddington, L Clewley, J Bergeron, G Cotter, S Dye, JE Geach, E Gonzalez-Solares, P Hirst, RJ Ivison, S Rawlings, C Simpson, GP Smith, A Verma, T Yamada

Abstract:

We analyse the first publicly released deep field of the UK Infrared Deep Sky Survey (UKIDSS) Deep eXtragalactic Survey to identify candidate galaxy overdensities at z ∼ 1 across ∼1 deg2 in the ELAIS-N1 field. Using I - K, J - K and K - 3.6 μm colours, we identify and spectroscopically follow up five candidate structures with Gemini/Gemini Multi-Object Spectrograph and confirm that they are all true overdensities with between five and 19 members each. Surprisingly, all five structures lie in a narrow redshift range at z = 0.89 ± 0.01, although they are spread across 30 Mpc on the sky. We also find a more distant overdensity at z = 1.09 in one of the spectroscopic survey regions. These five overdense regions lying in a narrow redshift range indicate the presence of a supercluster in this field and by comparing with mock cluster catalogues from N-body simulations we discuss the likely properties of this structure. Overall, we show that the properties of this supercluster are similar to the well-studied Shapley and Hercules superclusters at lower redshift. © 2007 RAS.
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Young galaxies in the early universe:: The physical properties of luminous z∼5 LBGs derived from their rest-frame UV to visible SEDs

AT THE EDGE OF THE UNIVERSE: LATEST RESULTS FROM THE DEEPEST ASTRONOMICAL SURVEYS 380 (2007) 75-+

Authors:

Aprajita Verma, Matthew Lehnert, Natascha Foerster Schreiber, Malcolm Bremer, Laura Douglas
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The rapid formation of a large rotating disk galaxy three billion years after the Big Bang

Nature 442:7104 (2006) 786-789

Authors:

R Genzel, LJ Tacconi, F Eisenhauer, NM Förster Schreiber, A Cimatti, E Daddi, N Bouché, R Davies, MD Lehnert, D Lutz, N Nesvadba, A Verma, R Abuter, K Shapiro, A Sternberg, A Renzini, X Kong, N Arimoto, M Mignoli

Abstract:

Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks - the primary components of present-day galaxies - were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger. © 2006 Nature Publishing Group.
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