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Atacama Compact Array Measurements of the Molecular Mass in the NGC 5044 Cooling-flow GroupSchellenberger, GerritDavid, Laurence P.Vrtilek, JanO'Sullivan, EwanLim, JeremyForman, WilliamSun, MingCombes, FrancoiseSalome, PhilippeJones, ChristineGiacintucci, SimonaEdge, AlastairGastaldello, FabioTemi, PasqualeBrighenti, FabrizioBardelli, SandroDOI: info:10.3847/1538-4357/ab879cv. 89472
Schellenberger, Gerrit, David, Laurence P., Vrtilek, Jan, O'Sullivan, Ewan, Lim, Jeremy, Forman, William, Sun, Ming, Combes, Francoise, Salome, Philippe, Jones, Christine, Giacintucci, Simona, Edge, Alastair, Gastaldello, Fabio, Temi, Pasquale, Brighenti, Fabrizio, and Bardelli, Sandro. 2020. "Atacama Compact Array Measurements of the Molecular Mass in the NGC 5044 Cooling-flow Group." The Astrophysical Journal 894:72.
ID: 156917
Type: article
Authors: Schellenberger, Gerrit; David, Laurence P.; Vrtilek, Jan; O'Sullivan, Ewan; Lim, Jeremy; Forman, William; Sun, Ming; Combes, Francoise; Salome, Philippe; Jones, Christine; Giacintucci, Simona; Edge, Alastair; Gastaldello, Fabio; Temi, Pasquale; Brighenti, Fabrizio; Bardelli, Sandro
Abstract: The fate of cooling gas in the centers of galaxy clusters and groups is still not well understood, as is also the case for the complex processes of triggering star formation in central dominant galaxies, reheating of cooled gas by active galactic nuclei (AGN), and the triggering or "feeding" of supermassive black hole outbursts. We present CO observations of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow. For our analysis we combine CO(2-1) data from the 7 m antennae of the Atacama Compact Array (ACA) and the ACA total power array (TP). We demonstrate, using the 7 m array data, that we can recover the total flux inferred from IRAM 30 m single-dish observations, which corresponds to a total molecular mass of about 4 × 107M. Most of the recovered flux is blueshifted with respect to the galaxy rest frame and is extended on kiloparsec-scales, suggesting low filling factor dispersed clouds. We find eight concentrations of molecular gas out to a radius of 10″ (1.5 kpc), which we identify with giant molecular clouds. The total molecular gas mass is more centrally concentrated than the X-ray emitting gas, but is extended in the northeast-southwest direction beyond the IRAM 30 m beam. We also compare the spatial extent of the molecular gas to the Hα emission: The CO emission coincides with the very bright Hα region in the center. We do not detect CO emission in the fainter Hα regions. Furthermore, we find two CO absorption features spatially located at the center of the galaxy, within 5 pc projected distance of the AGN, infalling at 255 and 265 km s-1 relative to the AGN. This indicates that the two giant molecular clouds seen in absorption are most likely within the sphere of influence of the supermassive black hole.
The ALMA Discovery of the Rotating Disk and Fast Outflow of Cold Molecular Gas in NGC 1275Nagai, H.Onishi, K.Kawakatu, N.Fujita, Y.Kino, M.Fukazawa, Y.Lim, J.Forman, WilliamVrtilek, JanNakanishi, K.Noda, H.Asada, K.Wajima, K.Ohyama, Y.David, LaurenceDaikuhara, K.DOI: info:10.3847/1538-4357/ab3e6ev. 883193
Nagai, H., Onishi, K., Kawakatu, N., Fujita, Y., Kino, M., Fukazawa, Y., Lim, J., Forman, William, Vrtilek, Jan, Nakanishi, K., Noda, H., Asada, K., Wajima, K., Ohyama, Y., David, Laurence, and Daikuhara, K. 2019. "The ALMA Discovery of the Rotating Disk and Fast Outflow of Cold Molecular Gas in NGC 1275." The Astrophysical Journal 883:193.
ID: 154705
Type: article
Authors: Nagai, H.; Onishi, K.; Kawakatu, N.; Fujita, Y.; Kino, M.; Fukazawa, Y.; Lim, J.; Forman, William; Vrtilek, Jan; Nakanishi, K.; Noda, H.; Asada, K.; Wajima, K.; Ohyama, Y.; David, Laurence; Daikuhara, K.
Abstract: We present observations using the Atacama Large Millimeter/submillimeter Array of the CO(2-1), HCN(3-2), and HCO+(3-2) lines in the nearby radio galaxy/brightest cluster galaxy (BCG) NGC 1275 with a spatial resolution of ̃20 pc. In previous observations, the CO(2-1) emission was detected as radial filaments lying in the east-west direction on a kiloparsec scale. We resolved the inner filament and found that it cannot be represented by a simple infalling stream on a sub-kiloparsec scale. The observed complex nature of the filament resembles the cold gas structure predicted by numerical simulations of cold chaotic accretion. Within the central 100 pc, we detected a rotational disk of molecular gas whose mass is ̃108 M . This is the first evidence of the presence of a massive cold gas disk on this spatial scale for BCGs. A crude estimate suggests that the accretion rate of the cold gas can be higher than that of hot gas. The disk rotation axis is approximately consistent with the radio- jet axis. This probably suggests that the cold gas disk is physically connected to the innermost accretion disk, which is responsible for jet launching. We also detected absorption features in the HCN(3-2) and HCO+(3-2) spectra against the radio continuum emission mostly radiated by a jet of size ̃1.2 pc. The absorption features are blueshifted from the systemic velocity by ̃300-600 km s-1, suggesting the presence of outflowing gas from the active galactic nucleus (AGN). We discuss the relation of the AGN feeding with cold accretion, the origin of blueshifted absorption, and an estimate of the black hole mass using molecular gas dynamics.
Building a cluster: shocks, cavities, and cooling filaments in the group-group merger NGC 6338O'Sullivan, EwanSchellenberger, GerritBurke, Douglas J.Sun, MingVrtilek, Jan M.David, Laurence P.Sarazin, CraigDOI: info:10.1093/mnras/stz1711v. 4882925–2946
O'Sullivan, Ewan, Schellenberger, Gerrit, Burke, Douglas J., Sun, Ming, Vrtilek, Jan M., David, Laurence P., and Sarazin, Craig. 2019. "Building a cluster: shocks, cavities, and cooling filaments in the group-group merger NGC 6338." Monthly Notices of the Royal Astronomical Society 488:2925– 2946.
ID: 154444
Type: article
Authors: O'Sullivan, Ewan; Schellenberger, Gerrit; Burke, Douglas J.; Sun, Ming; Vrtilek, Jan M.; David, Laurence P.; Sarazin, Craig
Abstract: We present deep Chandra, XMM-Newton, Giant Metrewave Radio Telescope, and Hα observations of the group-group merger NGC 6338. X-ray imaging and spectral mapping show that as well as trailing tails of cool, enriched gas, the two cool cores are embedded in an extensive region of shock-heated gas with temperatures rising to ̃5 keV. The velocity distribution of the member galaxies show that the merger is occurring primarily along the line of sight, and we estimate that the collision has produced shocks of Mach number M = 2.3 or greater, making this one of the most violent mergers yet observed between galaxy groups. Both cool cores host potential AGN cavities and Hα nebulae, indicating rapid radiative cooling. In the southern cool core around NGC 6338, we find that the X-ray filaments associated with the Hα nebula have low entropies (2) and short cooling times (̃200-300 Myr). In the northern core, we identify an Hα cloud associated with a bar of dense, cool X-ray gas offset from the dominant galaxy. We find no evidence of current jet activity in either core. We estimate the total mass of the system and find that the product of this group-group merger will likely be a galaxy cluster.
Forming One of the Most Massive Objects in the Universe: The Quadruple Merger in Abell 1758Schellenberger, GerritDavid, LaurenceO'Sullivan, EwanVrtilek, Jan M.Haines, C. P.DOI: info:10.3847/1538-4357/ab35e4v. 88259
Schellenberger, Gerrit, David, Laurence, O'Sullivan, Ewan, Vrtilek, Jan M., and Haines, C. P. 2019. "Forming One of the Most Massive Objects in the Universe: The Quadruple Merger in Abell 1758." The Astrophysical Journal 882:59.
ID: 154403
Type: article
Authors: Schellenberger, Gerrit; David, Laurence; O'Sullivan, Ewan; Vrtilek, Jan M.; Haines, C. P.
Abstract: The system A1758 is made up of two galaxy clusters, a more massive, northern cluster and a southern cluster. Both parts are undergoing major merger events at different stages. Although the mass of the merger constituents provides enough energy to produce visible shock fronts in the X-ray, none have been found to date. We present detailed temperature and abundance maps based on Chandra ACIS data and identify several candidates for shocks and cold fronts from a smoothed gradient map of the surface brightness. One candidate can be confirmed as the missing shock front in the northern cluster through X-ray spectroscopy. Nonthermal radio emission observed with the GMRT confirms the presence of radio halos in the northern and southern clusters and shows evidence for a relic in the periphery of the southern cluster. We do not find evidence for shocked gas between A1758 N and A1758 S.
The origin of the X-ray, radio and H I structures in the NGC 5903 galaxy groupO'Sullivan, EwanKolokythas, KonstantinosKantharia, Nimisha G.Raychaudhury, SomakDavid, Laurence P.Vrtilek, Jan M.DOI: info:10.1093/mnras/stx2702v. 4735248–5266
O'Sullivan, Ewan, Kolokythas, Konstantinos, Kantharia, Nimisha G., Raychaudhury, Somak, David, Laurence P., and Vrtilek, Jan M. 2018. "The origin of the X-ray, radio and H I structures in the NGC 5903 galaxy group." Monthly Notices of the Royal Astronomical Society 473:5248– 5266.
ID: 145789
Type: article
Authors: O'Sullivan, Ewan; Kolokythas, Konstantinos; Kantharia, Nimisha G.; Raychaudhury, Somak; David, Laurence P.; Vrtilek, Jan M.
Abstract: The NGC 5903 galaxy group is a nearby (∼30 Mpc) system of ∼30 members, dominated by the giant ellipticals NGC 5903 and NGC 5898. The group contains two unusual structures: a ∼110 kpc long H I filament crossing NGC 5903 and a ∼75 kpc wide diffuse, steep-spectrum radio source of unknown origin that overlaps NGC 5903 and appears to be partly enclosed by the H I filament. Using a combination of Chandra, XMM-Newton, Giant Meterwave Radio Telescope (GMRT) and Very Large Array (VLA) observations, we detect a previously unknown ∼0.65 keV intra-group medium filling the volume within 145 kpc of NGC 5903 and find a loop of enhanced X-ray emission extending ∼35 kpc south-west from the galaxy, enclosing the brightest part of the radio source. The northern and eastern parts of this X-ray structure are also strongly correlated with the southern parts of the H I filament. We determine the spectral index of the bright radio emission to be α _{150}^{612} = 1.03 ± 0.08, indicating a radiative age >360 Myr. We discuss the origin of the correlated radio, X-ray and H I structures, either through an interaction-triggered active galactic nucleus (AGN) outburst with enthalpy 1.8 × 1057 erg, or via a high-velocity collision between a galaxy and the H I filament. While neither scenario provides a complete explanation, we find that an AGN outburst is the most likely source of the principal X-ray and radio structures. However, it is clear that galaxy interactions continue to play an important role in the development of this relatively highly evolved galaxy group. We also resolve the question of whether the group member galaxy ESO 514-3 hosts a double-lobed radio source, confirming that the source is a superposed background AGN.
The Presence of Thermally Unstable X-Ray Filaments and the Production of Cold Gas in the NGC 5044 GroupDavid, Laurence P.Vrtilek, JanO'Sullivan, EwanJones, ChristineForman, WilliamSun, MingDOI: info:10.3847/1538-4357/aa756cv. 84284
David, Laurence P., Vrtilek, Jan, O'Sullivan, Ewan, Jones, Christine, Forman, William, and Sun, Ming. 2017. "The Presence of Thermally Unstable X-Ray Filaments and the Production of Cold Gas in the NGC 5044 Group." The Astrophysical Journal 842:84.
ID: 143363
Type: article
Authors: David, Laurence P.; Vrtilek, Jan; O'Sullivan, Ewan; Jones, Christine; Forman, William; Sun, Ming
Abstract: We present the results of a deep Chandra observation of the X-ray bright moderate-cooling flow group NGC 5044 along with the observed correlations between the ionized, atomic, and molecular gas in this system. The Chandra observation shows that the central AGN has undergone two outbursts in the past 108 years, based on the presence of two pairs of nearly bipolar X-ray cavities. The molecular gas and dust within the central 2 kpc is aligned with the orientation of the inner pair of bipolar X-ray cavities, suggesting that the most recent AGN outburst had a dynamical impact on the molecular gas. NGC 5044 also hosts many X-ray filaments within the central 8 kpc, but there are no obvious connections between the X-ray and Hα filaments and the more extended X-ray cavities that were inflated during the prior AGN outburst. Using the line width of the blended Fe-L line complex as a diagnostic for multiphase gas, we find that the majority of the multiphase thermally unstable gas in NGC 5044 is confined within the X-ray filaments. While the cooling time and entropy of the gas within the X-ray filaments are very similar, not all filaments show evidence of gas cooling or an association with Hα emission. We suggest that the various observed properties of the X-ray filaments are suggestive of an evolutionary sequence where thermally unstable gas begins to cool, becomes multiphased, develops Hα emitting plasma, and finally produces cold gas.
The Role of Electron Excitation and Nature of Molecular Gas in Cluster Central Elliptical GalaxiesLim, JeremyDinh-V-TrungVrtilek, JanDavid, Laurence P.Forman, WilliamDOI: info:10.3847/1538-4357/aa9275v. 85031
Lim, Jeremy, Dinh-V-Trung, Vrtilek, Jan, David, Laurence P., and Forman, William. 2017. "The Role of Electron Excitation and Nature of Molecular Gas in Cluster Central Elliptical Galaxies." The Astrophysical Journal 850:31.
ID: 144806
Type: article
Authors: Lim, Jeremy; Dinh-V-Trung; Vrtilek, Jan; David, Laurence P.; Forman, William
Abstract: We present observations in CO (3-2) that, combined with previous observations in CO (2-1), constrain the physical properties of the filamentary molecular gas in the central ~6.5 kpc of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We find this molecular gas to have a temperature ? 20 K and a density ~ {10}2{--}{10}4 {{cm}}-3, typically warmer and denser than the bulk of Giant Molecular Clouds (GMCs) in the Galaxy. Bathed in the harsh radiation and particle field of the surrounding intracluster X-ray gas, the molecular gas likely has a much higher ionization fraction than that of GMCs. For an ionization fraction of ~10-4, similar to that of Galactic diffuse (? 250 {{cm}}-3) partially molecular clouds that emit in HCN (1-0) and HCO+ (1-0), we show that the same gas traced in CO can produce the previously reported emissions in HCN (3-2), HCO+ (3-2), and CN (2-1) from NGC 1275; the dominant source of excitation for all the latter molecules is collisions with electrons. For the molecular filaments to not collapse, as evidenced by their lack of star formation, they must consist of thin strands that have cross-sectional radii ?0.2-2 pc if supported solely by thermal gas pressure; larger radii are permissible if turbulence or poloidal magnetic fields provide additional pressure support. We point out that the conditions required to relate CO luminosities to molecular gas masses in our Galaxy are unlikely to apply in cluster central elliptical galaxies. Rather than being virialized structures analogous to GMCs, we propose that the molecular gas in NGC 1275 comprises pressure-confined structures created by turbulent flows.
The Complete Local Volume Groups Sample - I. Sample selection and X-ray properties of the high-richness subsampleO'Sullivan, EwanPonman, Trevor J.Kolokythas, KonstantinosRaychaudhury, SomakBabul, ArifVrtilek, Jan M.David, Laurence P.Giacintucci, SimonaGitti, MyriamHaines, Chris P.DOI: info:10.1093/mnras/stx2078v. 4721482–1505
O'Sullivan, Ewan, Ponman, Trevor J., Kolokythas, Konstantinos, Raychaudhury, Somak, Babul, Arif, Vrtilek, Jan M., David, Laurence P., Giacintucci, Simona, Gitti, Myriam, and Haines, Chris P. 2017. "The Complete Local Volume Groups Sample - I. Sample selection and X-ray properties of the high-richness subsample." Monthly Notices of the Royal Astronomical Society 472:1482– 1505.
ID: 145637
Type: article
Authors: O'Sullivan, Ewan; Ponman, Trevor J.; Kolokythas, Konstantinos; Raychaudhury, Somak; Babul, Arif; Vrtilek, Jan M.; David, Laurence P.; Giacintucci, Simona; Gitti, Myriam; Haines, Chris P.
Abstract: We present the Complete Local-Volume Groups Sample (CLoGS), a statistically complete optically selected sample of 53 groups within 80 Mpc. Our goal is to combine X-ray, radio and optical data to investigate the relationship between member galaxies, their active nuclei and the hot intra-group medium (IGM). We describe sample selection, define a 26-group high-richness subsample of groups containing at least four optically bright (log LB ≥ 10.2 LB⊙) galaxies, and report the results of XMM-Newton and Chandra observations of these systems. We find that 14 of the 26 groups are X-ray bright, possessing a group-scale IGM extending at least 65 kpc and with luminosity >1041 erg s-1, while a further three groups host smaller galaxy-scale gas haloes. The X-ray bright groups have masses in the range M500 ≃ 0.5-5 × 1013 M, based on system temperatures of 0.4-1.4 keV, and X-ray luminosities in the range 2-200 × 1041 erg s-1. We find that ∼53-65 per cent of the X-ray bright groups have cool cores, a somewhat lower fraction than found by previous archival surveys. Approximately 30 per cent of the X-ray bright groups show evidence of recent dynamical interactions (mergers or sloshing), and ∼35 per cent of their dominant early-type galaxies host active galactic nuclei with radio jets. We find no groups with unusually high central entropies, as predicted by some simulations, and confirm that CLoGS is in principle capable of detecting such systems. We identify three previously unrecognized groups, and find that they are either faint (LX, R500 42 erg s-1) with no concentrated cool core, or highly disturbed. This leads us to suggest that ∼20 per cent of X-ray bright groups in the local universe may still be unidentified.
Chandra and Xmm-Newton Observations of the Bimodal Planck SZ-Detected Cluster Plckg345.40- 39.34 (A3716) with High and Low Entropy Subcluster CoresAndrade-Santos, FelipeJones, ChristineForman, William R.Murray, Stephen S.Kraft, Ralph P.Vikhlinin, Alexey A.van Weeren, Reinout J.Nulsen, Paul E. J.David, Laurence P.Dawson, William A.Arnaud, MoniquePointecouteau, EtiennePratt, Gabriel W.Melin, Jean-BaptisteDOI: info:10.1088/0004-637X/803/2/108v. 803108
Andrade-Santos, Felipe, Jones, Christine, Forman, William R., Murray, Stephen S., Kraft, Ralph P., Vikhlinin, Alexey A., van Weeren, Reinout J., Nulsen, Paul E. J., David, Laurence P., Dawson, William A., Arnaud, Monique, Pointecouteau, Etienne, Pratt, Gabriel W., and Melin, Jean-Baptiste. 2015. "Chandra and Xmm-Newton Observations of the Bimodal Planck SZ-Detected Cluster Plckg345.40- 39.34 (A3716) with High and Low Entropy Subcluster Cores." The Astrophysical Journal 803:108.
ID: 136003
Type: article
Authors: Andrade-Santos, Felipe; Jones, Christine; Forman, William R.; Murray, Stephen S.; Kraft, Ralph P.; Vikhlinin, Alexey A.; van Weeren, Reinout J.; Nulsen, Paul E. J.; David, Laurence P.; Dawson, William A.; Arnaud, Monique; Pointecouteau, Etienne; Pratt, Gabriel W.; Melin, Jean-Baptiste
Abstract: We present results from Chandra, XMM-Newton, and ROSAT observations of the Planck SZ-detected cluster A3716 (PLCKG345.40-39.34-G345). We show that G345 is, in fact, two subclusters separated on the sky by 400 kpc. We measure the subclusters' gas temperatures (~2-3 keV), total (~1-2 × 1014 {{M}o }) and gas (~1-2 × 1013 {{M}o }) masses, gas mass fraction within r500, entropy profiles, and X-ray luminosities (~1043 erg s-1). Using the gas density and temperature profiles for both subclusters, we show that there is good (0.8?) agreement between the expected Sunyaev-Zel'dovich signal predicted from the X-ray data and that measured from the Planck mission, and better agreement within 0.6? when we re-computed the Planck value assuming a two component cluster model, with relative amplitudes fixed based on the X-ray data. Dynamical analysis shows that the two galaxy subclusters are very likely (\gt 97% probability) gravitationally bound, and in the most likely scenario, the subclusters will undergo core passage in 500 ± 200 Myr. The northern subcluster is centrally peaked and has a low entropy core, while the southern subcluster has a high central entropy. The high central entropy in the southern subcluster can be explained either by the mergers of several groups, as suggested by the presence of five giant ellipticals or by active galactic nucleus energy injection, as suggested by the presence of a strong radio source in one of its massive elliptical galaxies, or by a combination of both processes.
A Very Deep Chandra Observation of A1795: The Cold Front and Cooling WakeEhlert, StevenMcDonald, MichaelDavid, Laurence P.Miller, Eric D.Bautz, Mark W.DOI: info:10.1088/0004-637X/799/2/174v. 799174
Ehlert, Steven, McDonald, Michael, David, Laurence P., Miller, Eric D., and Bautz, Mark W. 2015. "A Very Deep Chandra Observation of A1795: The Cold Front and Cooling Wake." The Astrophysical Journal 799:174.
ID: 135203
Type: article
Authors: Ehlert, Steven; McDonald, Michael; David, Laurence P.; Miller, Eric D.; Bautz, Mark W.
Abstract: We present a new analysis of very deep Chandra observations of the galaxy cluster A1795. Utilizing nearly 750 ks of net ACIS imaging, we are able to resolve the thermodynamic structure of the intracluster medium (ICM) on length scales of ~1 kpc near the cool core. We find several previously unresolved structures, including a high pressure feature to the north of the Brightest Cluster Galaxy (BCG) that appears to arise from the bulk motion of A1795's cool core. To the south of the cool core, we find low temperature ( {˜ } 3 \thinspace keV), diffuse ICM gas extending for distances of {˜ } 50 \thinspace kpc spatially coincident with previously identified filaments of Ha emission. Gas at similar temperatures is also detected in adjacent regions without any Ha emission. The X-ray gas coincident with the Ha filament has been measured to be cooling spectroscopically at a rate of {˜ } 1 M{? }\thinspace yr-1, consistent with measurements of the star formation rate in this region as inferred from ultraviolet (UV) observations, suggesting that the star formation in this filament as inferred by its Ha and UV emission can trace its origin to the rapid cooling of dense, X-ray emitting gas. The Ha filament is not a unique site of cooler ICM, however, as ICM at similar temperatures and even higher metallicities not cospatial with Ha emission is observed just to the west of the Ha filament, suggesting that it may have been uplifted by A1795's central active galaxy. Further simulations of cool core sloshing and active galactic nucleus feedback operating in concert with one another will be necessary to understand how such a dynamic cool core region may have originated and why the Ha emission is so localized with respect to the cool X-ray gas.
On the in-flight calibration plans of modern x-ray observatoriesGuainazzi, MatteoDavid, LaurenceGrant, Catherine E.Miller, EricNatalucci, LorenzoNevalainen, JukkaPetre, RobertAudard, MarcDOI: info:10.1117/1.JATIS.1.4.047001v. 1047001
Guainazzi, Matteo, David, Laurence, Grant, Catherine E., Miller, Eric, Natalucci, Lorenzo, Nevalainen, Jukka, Petre, Robert, and Audard, Marc. 2015. "On the in-flight calibration plans of modern x-ray observatories." Journal of Astronomical Telescopes, Instruments, and Systems 1:047001.
ID: 140568
Type: article
Authors: Guainazzi, Matteo; David, Laurence; Grant, Catherine E.; Miller, Eric; Natalucci, Lorenzo; Nevalainen, Jukka; Petre, Robert; Audard, Marc
Abstract: We present an overview of the set of celestial sources used for in-flight calibration of x-ray detectors by past and operational missions. We show the rationale behind their choice as a guideline for future missions aiming at optimizing the critical early phases of their science operations.
Molecular Gas in the X-Ray Bright Group NGC 5044 as Revealed by ALMADavid, Laurence P.Lim, JeremyForman, WilliamVrtilek, JanCombes, FrancoiseSalome, PhilippeEdge, AlastairHamer, StephenJones, ChristineSun, MingO'Sullivan, Ewan J.Gastaldello, FabioBardelli, SandroTemi, PasqualeSchmitt, HenriqueOhyama, YouichiMathews, WilliamBrighenti, FabrizioGiacintucci, SimonaTrung, Dinh-VDOI: info:10.1088/0004-637X/792/2/94v. 79294
David, Laurence P., Lim, Jeremy, Forman, William, Vrtilek, Jan, Combes, Francoise, Salome, Philippe, Edge, Alastair, Hamer, Stephen, Jones, Christine, Sun, Ming, O'Sullivan, Ewan J., Gastaldello, Fabio, Bardelli, Sandro, Temi, Pasquale, Schmitt, Henrique, Ohyama, Youichi, Mathews, William, Brighenti, Fabrizio, Giacintucci, Simona, and Trung, Dinh-V. 2014. "Molecular Gas in the X-Ray Bright Group NGC 5044 as Revealed by ALMA." The Astrophysical Journal 792:94.
ID: 130140
Type: article
Authors: David, Laurence P.; Lim, Jeremy; Forman, William; Vrtilek, Jan; Combes, Francoise; Salome, Philippe; Edge, Alastair; Hamer, Stephen; Jones, Christine; Sun, Ming; O'Sullivan, Ewan J.; Gastaldello, Fabio; Bardelli, Sandro; Temi, Pasquale; Schmitt, Henrique; Ohyama, Youichi; Mathews, William; Brighenti, Fabrizio; Giacintucci, Simona; Trung, Dinh-V
Abstract: An ALMA observation of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow, detected 24 molecular structures within the central 2.5 kpc. The masses of the molecular structures vary from 3 × 105 M ? to 107 M ? and the CO(2-1) linewidths vary from 15 to 65 km s-1. Given the large CO(2-1) linewidths, the observed structures are likely giant molecular associations (GMAs) and not individual giant molecular clouds (GMCs). Only a few of the GMAs are spatially resolved and the average density of these GMAs yields a GMC volume filling factor of about 15%. The masses of the resolved GMAs are insufficient for them to be gravitationally bound, however, the most massive GMA does contain a less massive component with a linewidth of 5.5 km s-1 (typical of an individual virialized GMC). We also show that the GMAs cannot be pressure confined by the hot gas. Given the CO(2-1) linewidths of the GMAs (i.e., the velocity dispersion of the embedded GMCs) they should disperse on a timescale of about 12 Myr. No disk-like molecular structures are detected and all indications suggest that the molecular gas follows ballistic trajectories after condensing out of the thermally unstable hot gas. The 230 GHz luminosity of the central continuum source is 500 times greater than its low frequency radio luminosity and probably reflects a recent accretion event. The spectrum of the central continuum source also exhibits an absorption feature with a linewidth typical of an individual GMC and an infalling velocity of 250 km s-1.
The impact of sloshing on the intragroup medium and old radio lobe of NGC 5044O'Sullivan, Ewan J.David, Laurence P.Vrtilek, Jan M.DOI: info:10.1093/mnras/stt1926v. 437730–739
O'Sullivan, Ewan J., David, Laurence P., and Vrtilek, Jan M. 2014. "The impact of sloshing on the intragroup medium and old radio lobe of NGC 5044." Monthly Notices of the Royal Astronomical Society 437:730– 739.
ID: 118823
Type: article
Authors: O'Sullivan, Ewan J.; David, Laurence P.; Vrtilek, Jan M.
Abstract: We present temperature and abundance maps of the central 125 kpc of the NGC 5044 galaxy group, based on a deep XMM-Newton observation. The abundance map reveals an asymmetrical abundance structure, with the centroid of the highest abundance gas offset ~22 kpc north-west of the galaxy centre, and moderate abundances extending almost twice as far to the south-east than in any other direction. The abundance distribution is closely correlated with two previously identified cold fronts and an arc-shaped region of surface brightness excess, and it appears that sloshing, induced by a previous tidal encounter, has produced both the abundance and surface brightness features. Sloshing dominates the uplift of heavy elements from the group core on large scales, and we estimate that the south-east extension (the tail of the sloshing spiral) contains at least 1.2 × 105 M? more iron than would be expected of gas at its radius. Placing limits on the age of the encounter we find that if, as previously suggested, the disturbed spiral galaxy NGC 5054 was the perturber, it must have been moving supersonically when it transited the group core. We also examine the spectral properties of emission from the old, detached radio lobe south-east of NGC 5044, and find that they are consistent with a purely thermal origin, ruling out this structure as a significant source of spectrally hard inverse-Compton emission.
A Merger Shock in A2034Owers, Matt S.Nulsen, Paul E. J.Couch, Warrick J.Ma, Cheng-JiunDavid, Laurence P.Forman, William R.Hopkins, Andrew M.Jones, Christinevan Weeren, Reinout J.DOI: info:10.1088/0004-637X/780/2/163v. 780163
Owers, Matt S., Nulsen, Paul E. J., Couch, Warrick J., Ma, Cheng-Jiun, David, Laurence P., Forman, William R., Hopkins, Andrew M., Jones, Christine, and van Weeren, Reinout J. 2014. "A Merger Shock in A2034." The Astrophysical Journal 780:163.
ID: 118826
Type: article
Authors: Owers, Matt S.; Nulsen, Paul E. J.; Couch, Warrick J.; Ma, Cheng-Jiun; David, Laurence P.; Forman, William R.; Hopkins, Andrew M.; Jones, Christine; van Weeren, Reinout J.
Abstract: We present a 250 ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought. Within ~27° about the axis of symmetry of the edge, the density, temperature, and pressure drop abruptly by factors of 1.83^{+0.09}_{-0.08}, 1.85^{+0.41}_{-0.41}, and 3.4^{+0.8}_{-0.7}, respectively. This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front. We measure a Mach number M = 1.59^{+0.06}_{-0.07} and corresponding shock velocity v shock ~= 2057 km s–1. Using spectra collected at the MMT with the Hectospec multi-object spectrograph, we identify 328 spectroscopically confirmed cluster members. Significantly, we find a local peak in the projected galaxy density associated with a bright cluster galaxy that is located just ahead of the nose of the shock. The data are consistent with a merger viewed within ~23° of the plane of the sky. The merging subclusters are now moving apart along a north-south axis approximately 0.3 Gyr after a small impact parameter core passage. The gas core of the secondary subcluster, which was driving the shock, appears to have been disrupted by the merger. Without a driving "piston," we speculate that the shock is dying. Finally, we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma that has been overrun by the shock.
Hot X-Ray Coronae around Massive Spiral Galaxies: A Unique Probe of Structure Formation ModelsBogdán, ÁkosForman, William R.Vogelsberger, MarkBourdin, HervéSijacki, DeboraMazzotta, PasqualeKraft, Ralph P.Jones, ChristineGilfanov, MaratChurazov, EugeneDavid, Laurence P.DOI: info:10.1088/0004-637X/772/2/97v. 77297
Bogdán, Ákos, Forman, William R., Vogelsberger, Mark, Bourdin, Hervé, Sijacki, Debora, Mazzotta, Pasquale, Kraft, Ralph P., Jones, Christine, Gilfanov, Marat, Churazov, Eugene, and David, Laurence P. 2013. "Hot X-Ray Coronae around Massive Spiral Galaxies: A Unique Probe of Structure Formation Models." The Astrophysical Journal 772:97.
ID: 116777
Type: article
Authors: Bogdán, Ákos; Forman, William R.; Vogelsberger, Mark; Bourdin, Hervé; Sijacki, Debora; Mazzotta, Pasquale; Kraft, Ralph P.; Jones, Christine; Gilfanov, Marat; Churazov, Eugene; David, Laurence P.
Abstract: Luminous X-ray gas coronae in the dark matter halos of massive spiral galaxies are a fundamental prediction of structure formation models, yet only a few such coronae have been detected so far. In this paper, we study the hot X-ray coronae beyond the optical disks of two "normal" massive spirals, NGC 1961 and NGC 6753. Based on XMM-Newton X-ray observations, hot gaseous emission is detected to ~60 kpc—well beyond their optical radii. The hot gas has a best-fit temperature of kT ~ 0.6 keV and an abundance of ~0.1 Solar, and exhibits a fairly uniform distribution, suggesting that the quasi-static gas resides in hydrostatic equilibrium in the potential well of the galaxies. The bolometric luminosity of the gas in the (0.05-0.15)r 200 region (r 200 is the virial radius) is ~6 × 1040 erg s–1 for both galaxies. The baryon mass fractions of NGC 1961 and NGC 6753 are f b, NGC 1961 ~ 0.11 and f b, NGC 6753 ~ 0.09, which values fall short of the cosmic baryon fraction. The hot coronae around NGC 1961 and NGC 6753 offer an excellent basis to probe structure formation simulations. To this end, the observations are confronted with the moving mesh code AREPO and the smoothed particle hydrodynamics code GADGET. Although neither model gives a perfect description, the observed luminosities, gas masses, and abundances favor the AREPO code. Moreover, the shape and the normalization of the observed density profiles are better reproduced by AREPO within ~0.5r 200. However, neither model incorporates efficient feedback from supermassive black holes or supernovae, which could alter the simulated properties of the X-ray coronae. With the further advance of numerical models, the present observations will be essential in constraining the feedback effects in structure formation simulations.
The Diverse Hot Gas Content and Dynamics of Optically Similar Low-mass Elliptical GalaxiesBogdán, ÁkosDavid, Laurence P.Jones, ChristineForman, William R.Kraft, Ralph P.DOI: info:10.1088/0004-637X/758/1/65v. 75865
Bogdán, Ákos, David, Laurence P., Jones, Christine, Forman, William R., and Kraft, Ralph P. 2012. "The Diverse Hot Gas Content and Dynamics of Optically Similar Low-mass Elliptical Galaxies." The Astrophysical Journal 758:65.
ID: 113695
Type: article
Authors: Bogdán, Ákos; David, Laurence P.; Jones, Christine; Forman, William R.; Kraft, Ralph P.
Abstract: The presence of hot X-ray-emitting gas is ubiquitous in massive early-type galaxies. However, much less is known about the content and physical status of the hot X-ray gas in low-mass ellipticals. In the present paper, we study the X-ray gas content of four low-mass elliptical galaxies using archival Chandra X-ray observations. The sample galaxies, NGC 821, NGC 3379, NGC 4278, and NGC 4697, have approximately identical K-band luminosities, and hence stellar masses, yet their X-ray appearance is strikingly different. We conclude that the unresolved emission in NGC 821 and NGC 3379 is built up from a multitude of faint compact objects, such as coronally active binaries and cataclysmic variables. Despite the non-detection of X-ray gas, these galaxies may host low density, and hence low luminosity, X-ray gas components, which undergo an outflow driven by a Type Ia supernova (SN Ia). We detect hot X-ray gas with a temperature of kT ~ 0.35 keV in NGC 4278, the component of which has a steeper surface brightness distribution than the stellar light. Within the central 50'' (~3.9 kpc), the estimated gas mass is ~3 × 107 M &sun;, implying a gas mass fraction of ~0.06%. We demonstrate that the X-ray gas exhibits a bipolar morphology in the northeast-southwest direction, indicating that it may be outflowing from the galaxy. The mass and energy budget of the outflow can be maintained by evolved stars and SNe Ia, respectively. The X-ray gas in NGC 4697 has an average temperature of kT ~ 0.3 keV and a significantly broader distribution than the stellar light. The total gas mass within 90'' (~5.1 kpc) is ~2.1 × 108 M &sun;, hence the gas mass fraction is ~0.4%. Based on the distribution and physical parameters of the X-ray gas, we conclude that it is most likely in hydrostatic equilibrium, although a subsonic outflow may be present.
The Universal Gas Mass Fraction in Clusters of GalaxiesDavid, Laurence P.Jones, ChristineForman, WilliamDOI: info:10.1088/0004-637X/748/2/120v. 748120
David, Laurence P., Jones, Christine, and Forman, William. 2012. "The Universal Gas Mass Fraction in Clusters of Galaxies." The Astrophysical Journal 748:120.
ID: 111439
Type: article
Authors: David, Laurence P.; Jones, Christine; Forman, William
Abstract: We obtained a deep 150 ks Chandra observation of the optically selected cluster of galaxies, RCS 2318+0034, to investigate the gas mass fraction
Recurrent Radio Outbursts at the Center of the NGC 1407 Galaxy GroupGiacintucci, SimonaO'Sullivan, Ewan J.Clarke, Tracy E.Murgia, MatteoVrtilek, Jan M.Venturi, TizianaDavid, Laurence P.Raychaudhury, SomakAthreya, Ramana M.DOI: info:10.1088/0004-637X/755/2/172v. 755172
Giacintucci, Simona, O'Sullivan, Ewan J., Clarke, Tracy E., Murgia, Matteo, Vrtilek, Jan M., Venturi, Tiziana, David, Laurence P., Raychaudhury, Somak, and Athreya, Ramana M. 2012. "Recurrent Radio Outbursts at the Center of the NGC 1407 Galaxy Group." The Astrophysical Journal 755:172.
ID: 112709
Type: article
Authors: Giacintucci, Simona; O'Sullivan, Ewan J.; Clarke, Tracy E.; Murgia, Matteo; Vrtilek, Jan M.; Venturi, Tiziana; David, Laurence P.; Raychaudhury, Somak; Athreya, Ramana M.
Abstract: We present deep Giant Metrewave Radio Telescope (GMRT) radio observations at 240, 330, and 610 MHz of the complex radio source at the center of the NGC 1407 galaxy group. Previous GMRT observations at 240 MHz revealed faint, diffuse emission enclosing the central twin-jet radio galaxy. This has been interpreted as an indication of two possible radio outbursts occurring at different times. Both the inner double and diffuse components are detected in the new GMRT images at high levels of significance. Combining the GMRT observations with archival Very Large Array data at 1.4 and 4.9 GHz, we derive the total spectrum of both components. The inner double has a spectral index ? = 0.7, typical for active, extended radio galaxies, whereas the spectrum of the large-scale emission is very steep, with ? = 1.8 between 240 MHz and 1.4 GHz. The radiative age of the large-scale component is very long, ~300 Myr, compared to ~30 Myr estimated for the central double, confirming that the diffuse component was generated during a former cycle of activity of the central galaxy. The current activity have so far released an energy which is nearly one order of magnitude lower than that associated with the former outburst. The group x-ray emission in the Chandra and XMM -Newton images and extended radio emission show a similar swept-back morphology. We speculate that the two structures are both affected by the motion of the group core, perhaps due to the core sloshing in response to a recent encounter with the nearby elliptical galaxy NGC 1400.
Active-Galactic-Nucleus-Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy GroupDavid, Laurence P.O'Sullivan, Ewan J.Jones, ChristineGiacintucci, SimonaVrtilek, JanRaychaudhury, SomakNulsen, Paul E. J.Forman, William R.Sun, MingDonahue, MeganDOI: info:10.1088/0004-637X/728/2/162v. 728No. 2162
David, Laurence P., O'Sullivan, Ewan J., Jones, Christine, Giacintucci, Simona, Vrtilek, Jan, Raychaudhury, Somak, Nulsen, Paul E. J., Forman, William R., Sun, Ming, and Donahue, Megan. 2011. "Active-Galactic-Nucleus-Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy Group." The Astrophysical Journal 728 (2):162.
ID: 99077
Type: article
Authors: David, Laurence P.; O'Sullivan, Ewan J.; Jones, Christine; Giacintucci, Simona; Vrtilek, Jan; Raychaudhury, Somak; Nulsen, Paul E. J.; Forman, William R.; Sun, Ming; Donahue, Megan
A Combined Low-radio Frequency/X-ray Study of Galaxy Groups. I. Giant Metrewave Radio Telescope Observations at 235 MHz AND 610 MHzGiacintucci, SimonaO'Sullivan, Ewan J.Vrtilek, JanDavid, Laurence P.Raychaudhury, SomakVenturi, TizianaAthreya, Ramana M.Clarke, Tracy E.Murgia, MatteoMazzotta, PasqualeGitti, MyriamPonman, TrevorIshwara-Chandra, C. H.Jones, ChristineForman, William R.DOI: info:10.1088/0004-637X/732/2/95v. 73295
Giacintucci, Simona, O'Sullivan, Ewan J., Vrtilek, Jan, David, Laurence P., Raychaudhury, Somak, Venturi, Tiziana, Athreya, Ramana M., Clarke, Tracy E., Murgia, Matteo, Mazzotta, Pasquale, Gitti, Myriam, Ponman, Trevor, Ishwara-Chandra, C. H., Jones, Christine, and Forman, William R. 2011. "A Combined Low-radio Frequency/X-ray Study of Galaxy Groups. I. Giant Metrewave Radio Telescope Observations at 235 MHz AND 610 MHz." The Astrophysical Journal 732:95.
ID: 101189
Type: article
Authors: Giacintucci, Simona; O'Sullivan, Ewan J.; Vrtilek, Jan; David, Laurence P.; Raychaudhury, Somak; Venturi, Tiziana; Athreya, Ramana M.; Clarke, Tracy E.; Murgia, Matteo; Mazzotta, Pasquale; Gitti, Myriam; Ponman, Trevor; Ishwara-Chandra, C. H.; Jones, Christine; Forman, William R.
Abstract: We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGNs) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology, and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at gsim1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems and are typically associated with small, low-, or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties, and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that co-exist with current activity is found in six groups of the sample.