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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.

Prof. Matt Jarvis

Professor of Astrophysics

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Cosmology
  • Galaxy formation and evolution
  • Hintze Centre for Astrophysical Surveys
  • MeerKAT
  • Rubin-LSST
  • The Square Kilometre Array (SKA)
Matt.Jarvis@physics.ox.ac.uk
Telephone: 01865 (2)83654
Denys Wilkinson Building, room 703
  • About
  • Publications

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

Monthly Notices of the Royal Astronomical Society Oxford University Press 507:256 (2021) 2643-2658

Authors:

Fangxia An, M Vaccari, Ian Smail, Mj Jarvis, Ih Whittam, Cl Hale, S Jin, Jd Collier, E Daddi, J Delhaize, B Frank, Ej Murphy, M Prescott, S Sekhar, Ar Taylor, Y Ao, K Knowles, L Marchetti, Sm Randriamampandry, Z Randriamanakoto

Abstract:

We study the radio spectral properties of 2094 star-forming galaxies (SFGs) by combining our early science data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with VLA, GMRT radio data, and rich ancillary data in the COSMOS field. These SFGs are selected at VLA 3 GHz, and their flux densities from MeerKAT 1.3 GHz and GMRT 325 MHz imaging data are extracted using the ‘superdeblending’ technique. The median radio spectral index is α3GHz1.3GHz=−0.80±0.01 without significant variation across the rest-frame frequencies ∼1.3–10 GHz, indicating radio spectra dominated by synchrotron radiation. On average, the radio spectrum at observer-frame 1.3–3 GHz slightly steepens with increasing stellar mass with a linear fitted slope of β = −0.08 ± 0.01, which could be explained by age-related synchrotron losses. Due to the sensitivity of GMRT 325 MHz data, we apply a further flux density cut at 3 GHz (⁠S3GHz≥50μJy) and obtain a sample of 166 SFGs with measured flux densities at 325 MHz, 1.3 GHz, and 3 GHz. On average, the radio spectrum of SFGs flattens at low frequency with the median spectral indices of α1.3GHz325MHz=−0.59+0.02−0.03 and α3.0GHz1.3GHz=−0.74+0.01−0.02⁠. At low frequency, our stacking analyses show that the radio spectrum also slightly steepens with increasing stellar mass. By comparing the far-infrared-radio correlations of SFGs based on different radio spectral indices, we find that adopting α3GHz1.3GHz for k-corrections will significantly underestimate the infrared-to-radio luminosity ratio (qIR) for >17 per cent of the SFGs with measured flux density at the three radio frequencies in our sample, because their radio spectra are significantly flatter at low frequency (0.33–1.3 GHz).
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MIGHTEE-HI: discovery of an H I-rich galaxy group at z = 0.044 with MeerKAT

Monthly Notices of the Royal Astronomical Society Oxford University Press 506:2 (2021) 2753-2765

Authors:

Shilpa Ranchod, Roger P Deane, Anastasia Ponomareva, Tariq Blecher, Bradley S Frank, Matthew Jarvis, Natasha Maddox, Wanga Mulaudzi, Marcin Glowacki, Kelley M Hess, Madalina Tudorache, Nathan J Adams, Rebecca Bowler, Jordan D Collier, Russ Taylor, Lourdes Verdes-Montenegro

Abstract:

We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H I in this z ∼ 0.044 group, with a 3σ column density sensitivity of NHI=1.6×1020cm−2⁠. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H I total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of log10(Mdyn/M⊙)=12.32⁠, and is unusually gas-rich, with an H I-to-stellar mass ratio of log10(f∗HI)=−0.2⁠, which is 0.7 dex greater than expected. The group’s high H I content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H I in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope.
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Evolution of the galaxy stellar mass function: evidence for an increasing M* from z = 2 to the present day

Monthly Notices of the Royal Astronomical Society Oxford University Press 506:4 (2021) 4933-4951

Authors:

Nj Adams, Raa Bowler, Mj Jarvis, B Häußler, Cdp Lagos

Abstract:

Utilizing optical and near-infrared broad-band photometry covering >5 deg2 in two of the most well-studied extragalactic legacy fields (COSMOS and XMM-LSS), we measure the galaxy stellar mass function (GSMF) between 0.1 < z < 2.0. We explore in detail the effect of two source extraction methods (SExtractor and ProFound) in addition to the inclusion/exclusion of Spitzer IRAC 3.6 and 4.5 μm photometry when measuring the GSMF. We find that including IRAC data reduces the number of massive (log10(M/M⊙) > 11.25) galaxies found due to improved photometric redshift accuracy, but has little effect on the more numerous lower-mass galaxies. We fit the resultant GSMFs with double Schechter functions down to log10(M/M⊙) = 7.75 (9.75) at z = 0.1 (2.0) and find that the choice of source extraction software has no significant effect on the derived best-fitting parameters. However, the choice of methodology used to correct for the Eddington bias has a larger impact on the high-mass end of the GSMF, which can partly explain the spread in derived M* values from previous studies. Using an empirical correction to model the intrinsic GSMF, we find evidence for an evolving characteristic stellar mass with δlog10(M*/M⊙)/δz = −0.16±0.05(−0.11±0.05)⁠, when using SExtractor (ProFound). We argue that with widely quenched star formation rates in massive galaxies at low redshift (z < 0.5), additional growth via mergers is required in order to sustain such an evolution to a higher characteristic mass.
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The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation

Monthly Notices of the Royal Astronomical Society Royal Astronomical Society 506:4 (2021) 5888-5907

Authors:

C Macfarlane, Pn Best, J Sabater, G Gürkan, Matt Jarvis, Hja Röttgering, Rd Baldi, G Calistro Rivera, Kj Duncan, Lk Morabito, I Prandoni, E Retana-Montenegro

Abstract:

We examine the distribution of radio emission from ∼42 000 quasars from the Sloan Digital Sky Survey, as measured in the LOFAR Two-metre Sky Survey (LoTSS). We present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: active galactic nuclei (jets) and star formation. Our two-component model provides an excellent match to the observed radio flux density distributions across a wide range of redshifts and quasar optical luminosities; this suggests that the jet-launching mechanism operates in all quasars but with different powering efficiency. The wide distribution of jet powers allows for a smooth transition between the ‘radio-quiet’ and ‘radio-loud’ quasar regimes, without need for any explicit bimodality. The best-fitting model parameters indicate that the star formation rate of quasar host galaxies correlates strongly with quasar luminosity and also increases with redshift at least out to z ∼ 2. For a model where star formation rate scales as Lαbol(1+z)β⁠, we find α = 0.47 ± 0.01 and β = 1.61 ± 0.05, in agreement with far-infrared studies. Quasars contribute ≈0.15 per cent of the cosmic star formation rate density at z = 0.5, rising to 0.4 per cent by z ∼ 2. The typical radio jet power is seen to increase with both increasing optical luminosity and black hole mass independently, but does not vary with redshift, suggesting intrinsic properties govern the production of the radio jets. We discuss the implications of these results for the triggering of quasar activity and the launching of jets.
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Deep Extragalactic VIsible Legacy Survey (DEVILS): consistent multiwavelength photometry for the DEVILS regions (COSMOS, XMMLSS, and ECDFS)

Monthly Notices of the Royal Astronomical Society Oxford University Press 506:1 (2021) 256-287

Authors:

Ljm Davies, Je Thorne, Asg Robotham, S Bellstedt, Sp Driver, Nj Adams, M Bilicki, Raa Bowler, M Bravo, L Cortese, C Foster, Mw Grootes, B Haussler, A Hashemizadeh, Bw Holwerda, P Hurley, Mj Jarvis, C Lidman, N Maddox, M Meyer, M Paolillo, S Phillipps, M Radovich, M Siudek, M Vaccari, Ra Windhorst

Abstract:

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is an ongoing high-completeness, deep spectroscopic survey of ∼60 000 galaxies to Y < 21.2 mag, over ∼6 deg2 in three well-studied deep extragalactic fields: D10 (COSMOS), D02 (XMMLSS), and D03 (ECDFS). Numerous DEVILS projects all require consistent, uniformly derived and state-of-the-art photometric data with which to measure galaxy properties. Existing photometric catalogues in these regions either use varied photometric measurement techniques for different facilities/wavelengths leading to inconsistencies, older imaging data and/or rely on source detection and photometry techniques with known problems. Here, we use the PROFOUND image analysis package and state-of-the-art imaging data sets (including Subaru-HSC, VST-VOICE, VISTA-VIDEO, and UltraVISTA-DR4) to derive matched-source photometry in 22 bands from the FUV to 500 μm. This photometry is found to be consistent, or better, in colour analysis to previous approaches using fixed-size apertures (which are specifically tuned to derive colours), but produces superior total source photometry, essential for the derivation of stellar masses, star formation rates, star formation histories, etc. Our photometric catalogue is described in detail and, after internal DEVILS team projects, will be publicly released for use by the broader scientific community.
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