The Shocked POststarburst Galaxy Survey (SPOGS) aims to identify galaxies in the transitional phase between actively star-forming and quiescence with nebular lines that are excited from shocks rather ...than star formation processes. We explored the ultraviolet (UV) properties of objects with near-ultraviolet (NUV) and far-ultraviolet (FUV) photometry from archival GALEX data; 444 objects were detected in both bands, 365 in only the NUV, and 24 in only the FUV, for a total of 833 observed objects. We compared SPOGs to samples of star-forming galaxies (SFs), quiescent galaxies (Qs), classical E+A post-starburst galaxies, active galactic nuclei (AGN) host galaxies, and interacting galaxies. We found that SPOGs have a larger range in their FUV-NUV and NUV-r colors compared with most of the other samples, although all of our comparison samples occupied color space inside of the SPOGs region. On the basis of their UV colors, SPOGs are a heterogeneous group, possibly made up of a mixture of SFs, Qs, and/or AGN. Using Gaussian mixture models, we are able to recreate the distribution of FUV-NUV colors of SPOGs and E + A galaxies with different combinations of SFs, Qs, and AGN. We find that the UV colors of SPOGs require a >60% contribution from SFs, with either Qs or AGN representing the remaining contribution, while UV colors of E + A galaxies required a significantly lower fraction of SFs, supporting the idea that SPOGs are at an earlier point in their transition from quiescent to star-forming than E + A galaxies.
ABSTRACT We present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and ...hence we also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a source-dominated spectrum of the AGN out to keV. In gross terms, the NuSTAR spectrum of the AGN has the form of a power law ( ) absorbed by a neutral column density of . However, we also detect curvature in the hard ( keV) spectrum resulting from reflection by Compton-thick matter out of our line of sight to the X-ray source. Compton reflection, possibly from the outer accretion disk or obscuring torus, is required even permitting a high-energy cut off in the continuum source; the limit on the cut-off energy is keV(90% confidence). Interestingly, the absorbed power law plus reflection model leaves residuals suggesting the absorption/emission from a fast ( ), high column-density ( ), highly ionized ( ) wind. A second, even faster ionized wind component is also suggested by these data. We show that the ionized wind likely carries a significant mass and momentum flux, and may carry sufficient kinetic energy to exercise feedback on the host galaxy. If confirmed, the simultaneous presence of a strong wind and powerful jets in Cygnus A demonstrates that feedback from radio-jets and sub-relativistic winds are not mutually exclusive phases of AGN activity but can occur simultaneously.
Active galactic nucleus (AGN) feedback at z∼1−3 is believed to take place in the presence of thick columns of gas and dust, leading to heavily obscured systems that are challenging to detect at ...optical and X‐ray wavelengths but are transparent at radio and mid‐IR (MIR) wavelengths. MIR color diagnostics using the widefield infrared space explorer (WISE) observations can identify the most luminous and heavily obscured AGNs, which are believed to represent a transient phase of rapid massive black hole growth. By combining both mid‐IR and radio diagnostics, we have identified a sample of 155 ultraluminous and obscured quasars (0.4<z<3) selected to have extremely red mid‐IR colors in WISE and compact, bright (>7 mJy) radio emission in the NRAO VLA Sky Survey (NVSS) and Faint Images of the Radio Sky at Twenty‐one centimeters (FIRST). High‐resolution very large array (VLA) imaging has revealed compact source morphologies on angular scales <0.2″ (1.7 kpc at z∼2) for the majority of our sources. Broadband radio spectra of the entire sample, constructed from our 10 GHz VLA observations and archival radio data show that 63% of the sample has peaked or curved spectral shapes consistent with those typically seen in young radio AGN (e.g., gigahertz peaked spectrum GPS and compact steep spectrum CSS sources). Overall, our sample is consistent with a population of recently triggered, young radio jets caught in a unique evolutionary stage in which they reside in a dense interstellar medium (ISM).
We present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and hence we ...also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a source-dominated spectrum of the AGN out to >70 keV. In gross terms, the NuSTAR spectrum of the AGN has the form of a power law (Γ∼1.6−1.7) absorbed by a neutral column density of N{sub H}∼1.6×10{sup 23} cm{sup −2}. However, we also detect curvature in the hard (>10 keV) spectrum resulting from reflection by Compton-thick matter out of our line of sight to the X-ray source. Compton reflection, possibly from the outer accretion disk or obscuring torus, is required even permitting a high-energy cut off in the continuum source; the limit on the cut-off energy is E{sub cut}>111 keV(90% confidence). Interestingly, the absorbed power law plus reflection model leaves residuals suggesting the absorption/emission from a fast (15,000−26,000 km s{sup −1} ), high column-density (N{sub W}>3×10{sup 23} cm{sup −2}), highly ionized (ξ∼2500 erg cm s{sup −1}) wind. A second, even faster ionized wind component is also suggested by these data. We show that the ionized wind likely carries a significant mass and momentum flux, and may carry sufficient kinetic energy to exercise feedback on the host galaxy. If confirmed, the simultaneous presence of a strong wind and powerful jets in Cygnus A demonstrates that feedback from radio-jets and sub-relativistic winds are not mutually exclusive phases of AGN activity but can occur simultaneously.
Interactions are crucial for galaxy formation and profoundly affect their evolution. However, our understanding of the impact of interactions on star formation and activity of the central ...supermassive black hole remains incomplete. In the canonical picture of the interaction process, these processes are expected to undergo a strong enhancement, but some recent studies have not found this prediction to be true in a statistically meaningful sense. This thesis uses a sample of local interactions observed from the ultraviolet to the far-infrared and a suite of N-body hydrodynamic simulations of interactions to examine the evolution of star formation, stellar mass, dust properties, and spectral energy distributions (SEDs) over the interaction sequence. First, we present the SEDs of 31 interactions in 14 systems, which we fit with stellar population synthesis models combined with a thermal dust model. We examine the differences between mildly, moderately, and strongly interacting systems. The star formation rate (SFR), dust luminosity, and the 15-25 K dust component temperature increase as the interaction progresses from moderately to strongly interacting. However, the SFR per stellar mass remains constant across the interaction stages. Second, we create 14 hydrodynamic simulations of isolated and interacting galaxies and calculate simulated photometry in 25 bands using the SUNRISE radiative transfer code. By comparing observed and simulated SEDs, we identify the simulation properties necessary to reproduce an interaction's SED. The best matches originate from simulated systems of similar stellar mass, infrared luminosities, dust mass, and SFR to the observed systems. Although an SED alone is insufficient to identify the interaction stage, strongly interacting systems preferentially match SEDs from times close to coalescence in the simulations. Third, we describe a case study of a post-merger system, Fornax A, for which we constrain its parameters of its progenitors. Based on the excess dust mass in this elliptical galaxy, we estimate a spiral galaxy with a stellar mass of (1 − 6) × 1010 solar masses brought in ≈10% of Fornax A's current stellar mass. We describe the probable two-outburst history that created the radio lobes ∼0.4 Gyr ago and two cavities in the X-ray emission closer to the nucleus ∼0.1 Gyr ago.
We measured and modeled spectral energy distributions (SEDs) in 28 bands from the ultraviolet to the far-infrared (FIR) for 31 interacting galaxies in 14 systems. The sample is drawn from the Spitzer ...Interacting Galaxy Survey, which probes a range of galaxy interaction parameters at multiple wavelengths with an emphasis on the infrared bands. The subset presented in this paper consists of all galaxies for which FIR Herschel SPIRE observations are publicly available. Our SEDs combine the Herschel photometry with multi-wavelength data from Spitzer, GALEX, Swift UVOT, and 2MASS. While the shapes of the SEDs are broadly similar across our sample, strongly interacting galaxies typically have more mid-infrared emission relative to their near-infrared and FIR emission than weakly or moderately interacting galaxies. We modeled the full SEDs to derive host galaxy star formation rates (SFRs), specific star formation rates (sSFRs), stellar masses, dust temperatures, dust luminosities, and dust masses. We find increases in the dust luminosity and mass, SFR, and cold (15-25 K) dust temperature as the interaction progresses from moderately to strongly interacting and between non-interacting and strongly interacting galaxies. We also find increases in the SER between weakly and strongly interacting galaxies. In contrast, the sSFR remains unchanged across all the interaction stages. The ultraviolet photometry is crucial for constraining the age of the stellar population and the SFR, while dust mass is primarily determined by SPIRE photometry. The SFR derived from the SED modeling agrees well with rates estimated by proportionality relations that depend on infrared emission.
The Infrared Jet in 3C 31 Lanz, Lauranne; Bliss, Amelia; Kraft, Ralph P ...
Astrophysical journal/The Astrophysical journal,
04/2011, Letnik:
731, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We report the detection of infrared emission from the jet of the nearby Fanaroff-Riley type I radio galaxy 3C 31. The jet was detected with the IRAC instrument on Spitzer at 4.5 Delta *mm, 5.8 Delta ...*mm, and 8.0 Delta *mm out to 30'' (13 kpc) from the nucleus. We measure radio, infrared, optical, and X-ray fluxes in three regions along the jet determined by the infrared and X-ray morphology. Radio through X-ray spectra in these regions demonstrate that the emission can be interpreted as synchrotron emission from a broken power-law distribution of electron energies. We find significant differences in the high-energy spectra with increasing distance from the nucleus. Specifically, the high-energy slope increases from 0.86 to 1.72 from 1 kpc to 12 kpc along the jet, and the spectral break likewise increases in frequency along the jet from tens to hundreds of GHz to ~20 THz. Thus, the ratio of IR-to-X-ray flux in the jet increases by at least an order of magnitude with increasing distance from the nucleus. We argue that these changes cannot simply be the result of spectral aging and that there is ongoing particle acceleration through this region of the jet. The effects of mass loading, turbulence, and jet deceleration, however these processes modify the jet flow in detail, must be causing a change in the electron energy distribution and the efficiency of particle acceleration.
We present new estimates on the fraction of heavily X-ray obscured, Compton-thick (CT) active galactic nuclei (AGNs) out to a redshift of \(z \leq\) 0.8. From a sample of 540 AGNs selected by mid-IR ...(MIR) properties in observed X-ray survey fields, we forward model the observed-to-intrinsic X-ray luminosity ratio (\(R_{L_{\text{X}}}\)) with a Markov chain Monte Carlo (MCMC) simulation to estimate the total fraction of CT AGNs (\(f_{\text{CT}}\)), many of which are missed in typical X-ray observations. We create model \(N_{\text{H}}\) distributions and convert these to \(R_{L_{\text{X}}}\) using a set of X-ray spectral models. We probe the posterior distribution of our models to infer the population of X-ray non-detected sources. From our simulation we estimate a CT fraction of \(f_{\text{CT}}\) = \(\text{0.555}^{+\text{0.037}}_{-\text{0.032}}\). We perform an X-ray stacking analysis for sources in Chandra X-ray Observatory fields and find that the expected soft (0.5-2 keV) and hard (2-7 keV) observed fluxes drawn from our model to be within 0.48 and 0.12 dex of our stacked fluxes, respectively. Our results suggests at least 50% of all MIR-selected AGNs, possibly more, are Compton-thick (\(N_{\text{H}} \gtrsim\) 10\(^{\text{24}}\) cm\(^{-\text{2}}\)), which is in excellent agreement with other recent work using independent methods. This work indicates that the total number of AGNs is higher than can be identified using X-ray observations alone, highlighting the importance of a multiwavelength approach. A high \(f_{\text{CT}}\) also has implications for black hole (BH) accretion physics and supports models of BH and galaxy co-evolution that include periods of heavy obscuration.
Spitzer spectral maps reveal a disk of highly luminous, warm (>150 K) H2 in the center of the massive spiral galaxy Messier 58, which hosts a radio-loud AGN. The inner 2.6 kpc of the galaxy appears ...to be overrun by shocks from the radio jet cocoon. Gemini NIRI imaging of the H2 1-0 S(1) emission line, ALMA CO 2-1, and HST multiband imagery indicate that much of the molecular gas is shocked in-situ, corresponding to lanes of dusty molecular gas that spiral towards the galaxy nucleus. The CO 2-1 and ionized gas kinematics are highly disturbed, with velocity dispersion up to 300 km/s. Dissipation of the associated kinetic energy and turbulence, likely injected into the ISM by radio-jet driven outflows, may power the observed molecular and ionized gas emission from the inner disk. The PAH fraction and composition in the inner disk appear to be normal, in spite of the jet and AGN activity. The PAH ratios are consistent with excitation by the interstellar radiation field from old stars in the bulge, with no contribution from star formation. The phenomenon of jet-shocked H2 may substantially reduce star formation and help to regulate the stellar mass of the inner disk and supermassive black hole in this otherwise normal spiral galaxy. Similarly strong H2 emission is found at the centers of several nearby spiral and lenticular galaxies with massive bulges and radio-loud AGN.
It is well established that brightest cluster galaxies (BCGs), residing in the center of galaxy clusters, are typically massive and quenched galaxies with cD or elliptical morphology. An optical ...survey suggested that an exotic galaxy population, superluminous spiral and lenticular galaxies could be the BCGs of some galaxy clusters. Because the cluster membership and the centroid of a cluster cannot be accurately determined based solely on optical data, we followed up a sample of superluminous disk galaxies and their environment using XMM-Newton X-ray observations. Specifically, we explored seven superluminous spiral and lenticular galaxies that are candidate BCGs. We detected massive galaxy clusters around five superluminous disk galaxies and established that one superluminous spiral, 2MASX J16273931+3002239, is the central BCG of a galaxy cluster. The temperature and total mass of the cluster are \(kT_{\rm 500}=3.55^{+0.18}_{-0.20}\) keV and \(M_{\rm 500} = (2.39 \pm 0.19) \times 10^{14} \ \rm{M_{\odot}} \). We identified the central galaxies of the four clusters that do not host the superluminous disk galaxy at their cores and established that the centrals are massive elliptical galaxies. However, for two of the clusters, the offset superluminous spirals are brighter than the central galaxies, implying that the superluminous disk galaxies are the brightest cluster galaxies. Our results demonstrate that superluminous disk galaxies are rarely the central systems of galaxy clusters. This is likely because galactic disks are destroyed by major mergers, which are more frequent in high-density environments. We speculate that the disks of superluminous disk galaxies in cluster cores may have been re-formed due to mergers with a gas-rich satellite.
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