Black Holes and Extreme Astrophysics

We study the astrophysics of extreme environments, close to the black holes in active galactic nuclei (AGN). We are also exploring the interplay and relative importance of black hole accretion and star formation in galaxies, both in individual objects and in the cosmological context.

 

AEGIS-X

The All-Wavelength Extended Groth Strip International Survey (AEGIS) is a collaborative effort to obtain both deep imaging covering all major wavebands from X-ray to radio and optical spectroscopy over a large area of sky (0.5 - 1 deg2), with the aim of studying the panchromatic properties of galaxies over the last half of the Hubble time. As part of this survey we have obtained a total of 3.4 Ms of Chandra ACIS-I time to survey the region in the X-ray band. More information on the programme is available on our Chandra AEGIS-X web pages.

 

IXO: The International X-ray Observatory

The International X-ray Observatory (IXO) is the next generation X-ray telescope currently being planned by ESA, NASA and JAXA, and due for launch in 2021. IXO combines a large X-ray mirror with powerful new instrumentation that will explore the high energy Universe.

 

The primary science goals of IXO are to study the properties and evolution of accreting black holes, the energetics and dynamics of hot gas in large cosmic structures and feedback, the process which links these two phenomena.

 

Read more about IXO here

 

Iron K lines - Probing Accreting Supermassive Black Holes

The discovery of broad and redshifted Fe K lines in some Seyfert galaxies with the ASCA satellite was extremely significant as it provided the first evidence of a relativistic accretion disc around supermassive black holes.  The lines are a great tool to investigate the geometry and kinematics of the inner regions of AGN, which are otherwise unobservable. A comprehensive survey with the higher spectral resolution instrument, XMM-Newton, has shown that two thirds of Seyfert 1s possess a broad line with some cases further indicating a spinning black hole (Nandra et al. 2007). The figure shows the broad band spectrum and iron line profile (at 6.4 keV) of the Seyfert 1 galaxy MCG-6-30-15. Furthermore, all of the sample possess a narrow iron line, which suggests an origin in the essential component of unification theories, the molecular torus.  Analysis of the iron line variability has revealed complex behaviour with some objects showing the expected correlation between the line and continuum while others show no variability of the line at all (Bhayani & Nandra 2009).

 

AGN Activity in a High-z Protocluster in HS 1700+64

The progenitors of the clusters of galaxies we see in the local universe are known as 'protoclusters' - these high redshift structures are an ideal place to investigate the relationship between supermassive black holes, their host galaxies and the surrounding large-scale environment in the early (z>1.5) universe.  To this end, we obtained a ~200ks Chandra observation of a z=2.3 protocluster discovered in HS 1700+64, which is easily seen as a 'spike' in the redshift distribution of this field (above). Together with available spectroscopic and narrow-band data we used this information to determine the AGN content of the protocluster and its relation to the field.  The analysis reveals AGN activity is generally enhanced in the protocluster (Digby-North et al. 2010), which is possibly due to the accelerated growth and evolution of black holes and galaxies in these high-z dense regions.

 

Chandra survey of the SWIRE ELAIS-N1

 

If we are to fully grasp the true nature of AGN and the effect they have on their host galaxies, we need to investigate these objects at a variety of wavelengths. Thus we have obtained a set of overlapping 5ks pointings taken using the Chandra X-ray observatory to identify a population of X-ray selected AGN in a ~1 deg2 of the SWIRE ELAIS-N1 field. By combining this data with observations at wavelengths through UV to radio we will be able to create broad band Spectral Energy Distributions (SEDs) for the AGN sample. We can then test models for obscuration and unification by using MIR and FIR data to probe the AGN dust torus and its contribution to the total SED. The starburst-AGN connection can be investigated by estimating the star formation rate (SFR) using FIR observations (e.g. Rowan-Robinson 2000) and seeing if SFRs in X-ray sources are elevated with respect to other random galaxies. We also hope to examine the radio loudness distribution of our sample, in addition to how radio emission affects the broad band SED and if radio loudness is determined by jet emission.

 

Data Products for Chandra Surveys

The reduced data, data products and source catalogues for various Chandra surveys (CDF-N, CDF-S, Extended CDF-S, Elais-N1 and XBootes) are available for here.

 

Chandra ACIS-I PSF Table

A PSF look-up table for Chandra ACIS-I data has been calculated and is described and available for download here

 

STAFF:

Paul Nandra

Postdoctoral Research Associates:

Elise Laird

PhD Students:

Shyam Bhayani

Jonathan Digby-North

Cyprian Rangel

Past MEMBERS:

James Aird (2008)

- Postdoctoral Research Associate

- University of California

Murray Brightman

Antonis Georgakakis (2008)

- Researcher

- National Athens Observatory

Anna Lia Longinotti

- Postdoctoral Research Associate

- MIT Kavli Institute for Astrophysics and Space

Ivan Valtchanov

- Instrument and Calibration Scientist

- ESA-ESAC

Paul O'Neill