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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.

Ian Heywood

Visitor

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Galaxy formation and evolution
  • MeerKAT
  • Pulsars, transients and relativistic astrophysics
  • The Square Kilometre Array (SKA)
  • Breakthrough Listen
ian.heywood@physics.ox.ac.uk
  • About
  • Publications

The Galactic center chimneys: the base of the multiphase outflow of the Milky Way

Astronomy and Astrophysics European Southern Observatory 646 (2021) A66

Authors:

G Ponti, Mr Morris, E Churazov, I Heywood, Robert Fender

Abstract:

Context. Outflows and feedback are key ingredients of galaxy evolution. Evidence for an outflow arising from the Galactic center (GC) – the so-called GC chimneys – has recently been discovered at radio, infrared, and X-ray bands.
Aims. We undertake a detailed examination of the spatial relationships between the emission in the different bands in order to place constraints on the nature and history of the chimneys and to better understand their impact on the GC environment and their relation with Galactic scale outflows.
Methods. We compare X-ray, radio, and infrared maps of the central few square degrees.
Results. The X-ray, radio, and infrared emissions are deeply interconnected, affecting one another and forming coherent features on scales of hundreds of parsecs, therefore indicating a common physical link associated with the GC outflow. We debate the location of the northern chimney and suggest that it might be located on the front side of the GC because of a significant tilt of the chimneys toward us. We report the presence of strong shocks at the interface between the chimneys and the interstellar medium, which are traced by radio and warm dust emission. We observe entrained molecular gas outflowing within the chimneys, revealing the multiphase nature of the outflow. In particular, the molecular outflow produces a long, strong, and structured shock along the northwestern wall of the chimney. Because of the different dynamical times of the various components of the outflow, the chimneys appear to be shaped by directed large-scale winds launched at different epochs. The data support the idea that the chimneys are embedded in an (often dominant) vertical magnetic field, which likely diverges with increasing latitude. We observe that the thermal pressure associated with the hot plasma appears to be smaller than the ram pressure of the molecular outflow and the magnetic pressure. This leaves open the possibility that either the main driver of the outflow is more powerful than the observed hot plasma, or the chimneys represent a “relic” of past and more powerful activity.
Conclusions. These multiwavelength observations corroborate the idea that the chimneys represent the channel connecting the quasi-continuous, but intermittent, activity at the GC with the base of the Fermi bubbles. In particular, the prominent edges and shocks observed in the radio and mid-infrared bands testify to the most powerful, more recent outflows from the central parsecs of the Milky Way.
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MIGHTEE-HI: The H I emission project of the MeerKAT MIGHTEE survey

Astronomy and Astrophysics EDP Sciences 646:February 2021 (2021) A35

Authors:

N Maddox, Bs Frank, Aa Ponomareva, Matthew Jarvis, Eak Adams, R Davé, Ta Oosterloo, Mg Santos, Sl Blyth, M Glowacki, Rc Kraan-Korteweg, W Mulaudzi, B Namumba, I Prandoni, Sha Rajohnson, K Spekkens, Nj Adams, Raa Bowler, Jd Collier, I Heywood, S Sekhar, Ar Taylor

Abstract:

We present the H I emission project within the MIGHTEE survey, currently being carried out with the newly commissioned MeerKAT radio telescope. This is one of the first deep, blind, medium-wide interferometric surveys for neutral hydrogen (H I) ever undertaken, extending our knowledge of H I emission to z = 0.6. The science goals of this medium-deep, medium-wide survey are extensive, including the evolution of the neutral gas content of galaxies over the past 5 billion years. Simulations predict nearly 3000 galaxies over 0 <  z <  0.4 will be detected directly in H I, with statistical detections extending to z = 0.6. The survey allows us to explore H I as a function of galaxy environment, with massive groups and galaxy clusters within the survey volume. Additionally, the area is large enough to contain as many as 50 local galaxies with H I mass < 108 M⊙, which allows us to study the low-mass galaxy population. The 20 deg2 main survey area is centred on fields with exceptional multi-wavelength ancillary data, with photometry ranging from optical through far-infrared wavelengths, supplemented with multiple spectroscopic campaigns. We describe here the survey design and the key science goals. We also show first results from the Early Science observations, including kinematic modelling of individual sources, along with the redshift, H I, and stellar mass ranges of the sample to date.
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Observations of a radio-bright, X-ray obscured GRS 1915+105

(2021)

Authors:

SE Motta, JJE Kajava, M Giustini, DRA Williams, M Del Santo, R Fender, DA Green, I Heywood, L Rhodes, A Segreto, G Sivakoff, PA Woudt
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MIGHTEE: are giant radio galaxies more common than we thought?

Monthly Notices of the Royal Astronomical Society Oxford University Press 501:3 (2020) 3833-3845

Authors:

J Delhaize, Ian Heywood, M Prescott, Matthew Jarvis, I Delvecchio, Ih Whittam, Sv White, Mj Hardcastle, Cl Hale, J Afonso, Y Ao, M Brienza, M Brüggen, Jd Collier, E Daddi, M Glowacki, N Maddox, Lk Morabito, I Prandoni, Z Randriamanakoto, S Sekhar, F An, Nj Adams, S Blyth, Rebecca Bowler, L Leeuw, L Marchetti, Sm Randriamampandry, K Thorat, N Seymour, O Smirnov, Ar Taylor, C Tasse, M Vaccari

Abstract:

We report the discovery of two new giant radio galaxies (GRGs) using the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey. Both GRGs were found within a ∼1 deg2 region inside the COSMOS field. They have redshifts of z = 0.1656 and z = 0.3363 and physical sizes of 2.4 and 2.0 Mpc, respectively. Only the cores of these GRGs were clearly visible in previous high-resolution Very Large Array observations, since the diffuse emission of the lobes was resolved out. However, the excellent sensitivity and uv coverage of the new MeerKAT telescope allowed this diffuse emission to be detected. The GRGs occupy an unpopulated region of radio power – size parameter space. Based on a recent estimate of the GRG number density, the probability of finding two or more GRGs with such large sizes at z < 0.4 in a ∼1 deg2 field is only 2.7 × 10−6, assuming Poisson statistics. This supports the hypothesis that the prevalence of GRGs has been significantly underestimated in the past due to limited sensitivity to low surface brightness emission. The two GRGs presented here may be the first of a new population to be revealed through surveys like MIGHTEE that provide exquisite sensitivity to diffuse, extended emission.
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MIGHTEE: Are giant radio galaxies more common than we thought?

(2020)

Authors:

J Delhaize, I Heywood, M Prescott, MJ Jarvis, I Delvecchio, IH Whittam, SV White, MJ Hardcastle, CL Hale, J Afonso, Y Ao, M Brienza, M Brueggen, JD Collier, E Daddi, M Glowacki, N Maddox, LK Morabito, I Prandoni, Z Randriamanakoto, S Sekhar, Fangxia An, NJ Adams, S Blyth, RAA Bowler, L Leeuw, L Marchetti, SM Randriamampandry, K Thorat, N Seymour, O Smirnov, AR Taylor, C Tasse, M Vaccari
More details from the publisher
Details from ArXiV

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