Nazirah Jetha - Academia.edu (original) (raw)

Papers by Nazirah Jetha

Chandra Proposal, 2006

Wide angle tailed radio galaxies (WATs) contain small kpc-scale jets that flare suddenly. The rea... more Wide angle tailed radio galaxies (WATs) contain small kpc-scale jets that flare suddenly. The reason for this flaring is not understood, but previous Chandra observations suggest that it is due to the ISM/ICM interface. Here we propose observations of WATs with bent jets. Recent work suggests that high galaxy speeds are needed to bend the jets. If this is the case, then the ISM should be stripped, and jet flaring should not coincide with the interface. We intend to ascertain the presence of the ISM in bent WAT host galaxies, to determine if the interface is responsible for the jet flaring. This will enable a better understanding of the physics of AGN jets.

The X Ray Universe 2008, May 27, 2008

Heating by AGN is widely believed to be an important mechanism in solving the cluster centre `coo... more Heating by AGN is widely believed to be an important mechanism in solving the cluster centre `cooling flow problem', but direct observations of AGN heating are rare. We propose to observe the restarting radio source hosted by the BCG in the cluster Abell 695. This AGN is at the beginning of a duty cycle, and is feeding small young radio lobes which should be expanding supersonically and driving shocks into the ICM. This is the only cluster-centre source we are aware of where the radio and X-ray data are consistent with ongoing shock heating. We intend to search for signs of shock heating of the ICM, measure the temperature of any shocked material, and by comparison with systems such as Centaurus A, further our understanding of the important shock-heating phase of AGN cluster energy input.

Monthly Notices of the Royal Astronomical Society, 2007

ABSTRACT

The Astrophysical Journal, 2010

We present gas constraints from Sunyaev-Zel'dovich (SZ) effect measurements in a sample of eleven... more We present gas constraints from Sunyaev-Zel'dovich (SZ) effect measurements in a sample of eleven X-ray and infrared (IR) selected galaxy clusters at z ≥1, using data from the Sunyaev-Zel'dovich Array (SZA). The cylindrically integrated Compton-y parameter, Y , is calculated by fitting the data to a two-parameter gas pressure profile. Where possible, we also determine the temperature of the hot intra-cluster plasma from Chandra and XMM-Newton data, and constrain the gas mass within the same aperture (r 2500 ) as Y . The SZ effect is detected in the clusters for which the X-ray data indicate gas masses above ∼ 10 13 M , including XMMU J2235-2557 at redshift z = 1.39, which to date is one of the most distant clusters detected using the SZ effect. None of the IR-selected targets are detected by the SZA measurements, indicating low gas masses for these objects. For these and the four other undetected clusters, we quote upper limits on Y and M gas,SZ , with the latter derived from scaling relations calibrated with lower redshift clusters. We compare the constraints on Y and X-ray derived gas mass M gas,X-ray to self-similar scaling relations between these observables determined from observations of lower redshift clusters, finding consistency given the measurement error.

We present a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray obs... more We present a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new low frequency GMRT data. Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

Monthly Notices of The Royal Astronomical Society, 2008

We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the ... more We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4+1.0-0.5 into the interstellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the active galactic nuclei (AGN) spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by an AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium.

We present gas temperature, density, entropy and cooling time profiles for the cores of a sample ... more We present gas temperature, density, entropy and cooling time profiles for the cores of a sample of 15 galaxy groups observed with {\it Chandra}. We find that the entropy profiles follow a power-law profile down to very small fractions of R500R_{500}R500. Differences between the gas profiles of groups with radio loud and radio quiet BGGs are only marginally significant, and there is only a small difference in the LX:TXL_X:T_XLX:TX relations, for the central regions we study with {\it Chandra}, between the radio-loud and radio-quiet objects in our sample, in contrast to the much larger difference found on scales of the whole group in earlier work. However, there is evidence, from splitting the sample based on the mass of the central black holes, that repeated outbursts of AGN activity may have a long term cumulative effect on the entropy profiles. We argue that, to first-order, energy injection from radio sources does not change the global structure of the gas in the cores of groups, although it can displace gas on a local level. In most systems, it appears that AGN energy injection serves primarily to counter the effects of radiative cooling, rather than being responsible for the similarity breaking between groups and clusters.

We present the first of a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-New... more We present the first of a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new or forthcoming low frequency GMRT data -RXJ1416.4+2315 (z=0.137). Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

Monthly Notices of The Royal Astronomical Society, 2008

The nearby cluster Abell194 hosts two luminous, distorted radio galaxies. Both reside within the ... more The nearby cluster Abell194 hosts two luminous, distorted radio galaxies. Both reside within the cluster's core region, being separated in projection by only 100 kpc. It is often suggested that tailed radio galaxies such as these reside in clusters that are under formation and are accreting new material from their outskirts. In this paper, we study the intriguing appearance of Abell 194, and test whether the cluster and radio source dynamics are consistent with the cluster formation/merger model. We analyse data from the XMM-Newton satellite and previously unpublished observations with the Very Large Array as well as present new data from the Giant Metre-Wave Radio Telescope (GMRT). The shape of the jets, and the lack of significant stripping of the galaxies' interstellar media, indicates that the radio galaxies are not moving at the large velocities they would have had if they were falling into the cluster from its outskirts; galaxy velocities of <=300kms-1 are adequate instead. A plausible scenario that could explain the observations is that the dynamics of the cluster centre are relatively quiescent, with the dominant system of massive galaxies being bound and orbiting the cluster centre of mass. For plausible jet/plume speeds and densities and the galaxy dynamics implied by this picture of the cluster, we show that the observed jet structures can be explained without invoking a major cluster merger event.

Monthly Notices of The Royal Astronomical Society, 2008

We discuss the effects of energy injection into the intra-group medium of the group of galaxies a... more We discuss the effects of energy injection into the intra-group medium of the group of galaxies associated with NGC 741. The X-ray emission reveals a large bubble, which in the absence of a currently bright central radio source, may have been inflated by a previous cycle of nuclear activity . If the bubble is filled with a light, relativistic fluid we calculate that in expanding, it has done more than sufficient work to counteract the energy lost from the intra-group medium via radiative cooling; the bubble can provide this energy as it expands and rises. Using upper limits on the flux density of the plasma filling the bubble at 330 MHz and 1.4 GHz, we derive constraints on its electron energy distribution and magnetic field strength. We show that the data require the high-energy cut-off of the electron spectrum to be very low compared to the cut-offs seen in more typical radio sources if the fluid filling the bubble is a conventional relativistic plasma. This suggests that the fluid filling the bubble may not have evolved by expansion or synchrotron losses consistent with a dead radio source, leaving a puzzle as to what the origin of the bubble may be.

Monthly Notices of The Royal Astronomical Society, 2006

We present a sample of 30 wide angle tailed radio galaxies (WATs) that we use to constrain the je... more We present a sample of 30 wide angle tailed radio galaxies (WATs) that we use to constrain the jet speeds in these sources. We measure the distribution of jet-sidedness ratios for the sample, and assuming that the jets are beamed, jet speeds in the range (0.3-0.7)c are obtained. Whilst the core prominence of the sample, which ought to be a reliable indicator of beaming, shows little correlation with the jet-sidedness, we argue that due to the peculiar nature of WATs core-prominence is unlikely to be a good indicator of beaming in these sources. We further show that if the jets are fast and light, then the galaxy speeds required to bend jets into C-shapes such as those seen in 0647+693 are reasonable for a galaxy in a merging or recently merged cluster.

Monthly Notices of The Royal Astronomical Society, 2005

We present Chandra and Very Large Array observations of two galaxy clusters, Abell 160 and Abell ... more We present Chandra and Very Large Array observations of two galaxy clusters, Abell 160 and Abell 2462, whose brightest cluster galaxies (BCGs) host wide angle tailed radio galaxies (WATs). We search for evidence of interactions between the radio emission and the hot, X-ray emitting gas, and we test various jet termination models. We find that both clusters have cool BCGs at the cluster centre, and that the scale of these cores (~30-40 kpc for both sources) is of approximately the same scale as the length of the radio jets. For both sources, the jet flaring point is coincident with a steepening in the host cluster's temperature gradient, and similar results are found for 3C 465 and Hydra A. However, none of the published models of WAT formation offers a satisfactory explanation as to why this may be the case. Therefore, it is unclear what causes the sudden transition between the jet and the plume. Without accurate modelling, we cannot ascertain whether the steepening of the temperature gradient is the main cause of the transition, or merely a tracer of an underlying process.

Monthly Notices of The Royal Astronomical Society, 2008

We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the ... more We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4 +1.0 −0.5 into the inter-stellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the AGN spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium.

This work uses X-ray and radio data to examine the interaction between radio-loud AGN and their e... more This work uses X-ray and radio data to examine the interaction between radio-loud AGN and their environments. The first half of this work concentrates on how a cluster environment influences the morphology of wide-angle tailed radio sources (WATs). It is found that existing models of WAT formation are unable to explain the phenomenon in light of the data. It is argued that the cluster environment is responsible for determining the location of the plume base, and that conditions inside the plume determine the jet flaring. WATs with very bent jets are discussed in light of jet speeds inferred from a homogenous sample of WATs, and it appears that highly disturbed cluster environments are required for such bending. The second half of this thesis concentrates on whether radio sources can prevent catastrophic cooling. It is found that whilst there are some differences between groups with radio loud brightest galaxies and those without, it is unlikely that radio sources irreversibly raise the entropy in group centres. Rather, it appears that current radio sources act to prevent catastrophic cooling in the centres of groups, whilst repeated outbursts may have a longer lasting effect, particularly if the physical size of the outburst is large.

Chandra Proposal, 2006

Wide angle tailed radio galaxies (WATs) contain small kpc-scale jets that flare suddenly. The rea... more Wide angle tailed radio galaxies (WATs) contain small kpc-scale jets that flare suddenly. The reason for this flaring is not understood, but previous Chandra observations suggest that it is due to the ISM/ICM interface. Here we propose observations of WATs with bent jets. Recent work suggests that high galaxy speeds are needed to bend the jets. If this is the case, then the ISM should be stripped, and jet flaring should not coincide with the interface. We intend to ascertain the presence of the ISM in bent WAT host galaxies, to determine if the interface is responsible for the jet flaring. This will enable a better understanding of the physics of AGN jets.

The X Ray Universe 2008, May 27, 2008

Heating by AGN is widely believed to be an important mechanism in solving the cluster centre `coo... more Heating by AGN is widely believed to be an important mechanism in solving the cluster centre `cooling flow problem', but direct observations of AGN heating are rare. We propose to observe the restarting radio source hosted by the BCG in the cluster Abell 695. This AGN is at the beginning of a duty cycle, and is feeding small young radio lobes which should be expanding supersonically and driving shocks into the ICM. This is the only cluster-centre source we are aware of where the radio and X-ray data are consistent with ongoing shock heating. We intend to search for signs of shock heating of the ICM, measure the temperature of any shocked material, and by comparison with systems such as Centaurus A, further our understanding of the important shock-heating phase of AGN cluster energy input.

Monthly Notices of the Royal Astronomical Society, 2007

ABSTRACT

The Astrophysical Journal, 2010

We present gas constraints from Sunyaev-Zel'dovich (SZ) effect measurements in a sample of eleven... more We present gas constraints from Sunyaev-Zel'dovich (SZ) effect measurements in a sample of eleven X-ray and infrared (IR) selected galaxy clusters at z ≥1, using data from the Sunyaev-Zel'dovich Array (SZA). The cylindrically integrated Compton-y parameter, Y , is calculated by fitting the data to a two-parameter gas pressure profile. Where possible, we also determine the temperature of the hot intra-cluster plasma from Chandra and XMM-Newton data, and constrain the gas mass within the same aperture (r 2500 ) as Y . The SZ effect is detected in the clusters for which the X-ray data indicate gas masses above ∼ 10 13 M , including XMMU J2235-2557 at redshift z = 1.39, which to date is one of the most distant clusters detected using the SZ effect. None of the IR-selected targets are detected by the SZA measurements, indicating low gas masses for these objects. For these and the four other undetected clusters, we quote upper limits on Y and M gas,SZ , with the latter derived from scaling relations calibrated with lower redshift clusters. We compare the constraints on Y and X-ray derived gas mass M gas,X-ray to self-similar scaling relations between these observables determined from observations of lower redshift clusters, finding consistency given the measurement error.

We present a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray obs... more We present a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new low frequency GMRT data. Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

Monthly Notices of The Royal Astronomical Society, 2008

We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the ... more We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4+1.0-0.5 into the interstellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the active galactic nuclei (AGN) spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by an AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium.

We present gas temperature, density, entropy and cooling time profiles for the cores of a sample ... more We present gas temperature, density, entropy and cooling time profiles for the cores of a sample of 15 galaxy groups observed with {\it Chandra}. We find that the entropy profiles follow a power-law profile down to very small fractions of R500R_{500}R500. Differences between the gas profiles of groups with radio loud and radio quiet BGGs are only marginally significant, and there is only a small difference in the LX:TXL_X:T_XLX:TX relations, for the central regions we study with {\it Chandra}, between the radio-loud and radio-quiet objects in our sample, in contrast to the much larger difference found on scales of the whole group in earlier work. However, there is evidence, from splitting the sample based on the mass of the central black holes, that repeated outbursts of AGN activity may have a long term cumulative effect on the entropy profiles. We argue that, to first-order, energy injection from radio sources does not change the global structure of the gas in the cores of groups, although it can displace gas on a local level. In most systems, it appears that AGN energy injection serves primarily to counter the effects of radiative cooling, rather than being responsible for the similarity breaking between groups and clusters.

We present the first of a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-New... more We present the first of a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new or forthcoming low frequency GMRT data -RXJ1416.4+2315 (z=0.137). Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

Monthly Notices of The Royal Astronomical Society, 2008

The nearby cluster Abell194 hosts two luminous, distorted radio galaxies. Both reside within the ... more The nearby cluster Abell194 hosts two luminous, distorted radio galaxies. Both reside within the cluster's core region, being separated in projection by only 100 kpc. It is often suggested that tailed radio galaxies such as these reside in clusters that are under formation and are accreting new material from their outskirts. In this paper, we study the intriguing appearance of Abell 194, and test whether the cluster and radio source dynamics are consistent with the cluster formation/merger model. We analyse data from the XMM-Newton satellite and previously unpublished observations with the Very Large Array as well as present new data from the Giant Metre-Wave Radio Telescope (GMRT). The shape of the jets, and the lack of significant stripping of the galaxies' interstellar media, indicates that the radio galaxies are not moving at the large velocities they would have had if they were falling into the cluster from its outskirts; galaxy velocities of <=300kms-1 are adequate instead. A plausible scenario that could explain the observations is that the dynamics of the cluster centre are relatively quiescent, with the dominant system of massive galaxies being bound and orbiting the cluster centre of mass. For plausible jet/plume speeds and densities and the galaxy dynamics implied by this picture of the cluster, we show that the observed jet structures can be explained without invoking a major cluster merger event.

Monthly Notices of The Royal Astronomical Society, 2008

We discuss the effects of energy injection into the intra-group medium of the group of galaxies a... more We discuss the effects of energy injection into the intra-group medium of the group of galaxies associated with NGC 741. The X-ray emission reveals a large bubble, which in the absence of a currently bright central radio source, may have been inflated by a previous cycle of nuclear activity . If the bubble is filled with a light, relativistic fluid we calculate that in expanding, it has done more than sufficient work to counteract the energy lost from the intra-group medium via radiative cooling; the bubble can provide this energy as it expands and rises. Using upper limits on the flux density of the plasma filling the bubble at 330 MHz and 1.4 GHz, we derive constraints on its electron energy distribution and magnetic field strength. We show that the data require the high-energy cut-off of the electron spectrum to be very low compared to the cut-offs seen in more typical radio sources if the fluid filling the bubble is a conventional relativistic plasma. This suggests that the fluid filling the bubble may not have evolved by expansion or synchrotron losses consistent with a dead radio source, leaving a puzzle as to what the origin of the bubble may be.

Monthly Notices of The Royal Astronomical Society, 2006

We present a sample of 30 wide angle tailed radio galaxies (WATs) that we use to constrain the je... more We present a sample of 30 wide angle tailed radio galaxies (WATs) that we use to constrain the jet speeds in these sources. We measure the distribution of jet-sidedness ratios for the sample, and assuming that the jets are beamed, jet speeds in the range (0.3-0.7)c are obtained. Whilst the core prominence of the sample, which ought to be a reliable indicator of beaming, shows little correlation with the jet-sidedness, we argue that due to the peculiar nature of WATs core-prominence is unlikely to be a good indicator of beaming in these sources. We further show that if the jets are fast and light, then the galaxy speeds required to bend jets into C-shapes such as those seen in 0647+693 are reasonable for a galaxy in a merging or recently merged cluster.

Monthly Notices of The Royal Astronomical Society, 2005

We present Chandra and Very Large Array observations of two galaxy clusters, Abell 160 and Abell ... more We present Chandra and Very Large Array observations of two galaxy clusters, Abell 160 and Abell 2462, whose brightest cluster galaxies (BCGs) host wide angle tailed radio galaxies (WATs). We search for evidence of interactions between the radio emission and the hot, X-ray emitting gas, and we test various jet termination models. We find that both clusters have cool BCGs at the cluster centre, and that the scale of these cores (~30-40 kpc for both sources) is of approximately the same scale as the length of the radio jets. For both sources, the jet flaring point is coincident with a steepening in the host cluster's temperature gradient, and similar results are found for 3C 465 and Hydra A. However, none of the published models of WAT formation offers a satisfactory explanation as to why this may be the case. Therefore, it is unclear what causes the sudden transition between the jet and the plume. Without accurate modelling, we cannot ascertain whether the steepening of the temperature gradient is the main cause of the transition, or merely a tracer of an underlying process.

Monthly Notices of The Royal Astronomical Society, 2008

We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the ... more We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4 +1.0 −0.5 into the inter-stellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the AGN spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium.

This work uses X-ray and radio data to examine the interaction between radio-loud AGN and their e... more This work uses X-ray and radio data to examine the interaction between radio-loud AGN and their environments. The first half of this work concentrates on how a cluster environment influences the morphology of wide-angle tailed radio sources (WATs). It is found that existing models of WAT formation are unable to explain the phenomenon in light of the data. It is argued that the cluster environment is responsible for determining the location of the plume base, and that conditions inside the plume determine the jet flaring. WATs with very bent jets are discussed in light of jet speeds inferred from a homogenous sample of WATs, and it appears that highly disturbed cluster environments are required for such bending. The second half of this thesis concentrates on whether radio sources can prevent catastrophic cooling. It is found that whilst there are some differences between groups with radio loud brightest galaxies and those without, it is unlikely that radio sources irreversibly raise the entropy in group centres. Rather, it appears that current radio sources act to prevent catastrophic cooling in the centres of groups, whilst repeated outbursts may have a longer lasting effect, particularly if the physical size of the outburst is large.