Search

We quantify the luminosity contribution of active galactic nuclei (AGN) to the 12 $\mu$m, mid-infrared (MIR; 5-38 $\mu$m), and the total IR (5-1000 $\mu$m) emission in the local AGN detected in the all-sky 70-month Swift/Burst Alert Telescope (BAT) ultra hard X-ray survey. We decompose the IR spectral energy distributions (SEDs) of 587 objects into AGN and starburst components using AGN torus and star-forming galaxy templates. This enables us to recover the AGN torus emission also for low-luminosity end, down to $\log (L_{14-150}/{\rm erg}~{\rm s}^{-1}) \simeq 41$, which typically have significant host galaxy contamination. We find that the luminosity contribution of the AGN to the 12 $\mu$m, the MIR, and the total IR band is an increasing function of the 14-150 keV luminosity. We also find that for the most extreme cases, the IR pure-AGN emission from the torus can extend up to 90 $\mu$m. The obtained total IR AGN luminosity through the IR SED decomposition enables us to estimate the fraction of the sky obscured by dust, i.e., the dust covering factor. We demonstrate that the median of the dust covering factor is always smaller than that of the X-ray obscuration fraction above the AGN bolometric luminosity of $\log (L_{\rm bol}/{\rm erg}~{\rm s}^{-1}) \simeq 42.5$. Considering that X-ray obscuration fraction is equivalent to the covering factor coming from both the dust and gas, it indicates that an additional neutral gas component, along with the dusty torus, is responsible for the absorption of X-ray emission., Comment: 21 pages, 15 figures, accepted for publication in ApJ. The full list of Table 1 is available at http://www.kusastro.kyoto-u.ac.jp/~ichikawa/Table1_MR_20181107.txt

We present simultaneous XMM-Newton and NuSTAR observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with sub-arcminute resolution at X-ray energies above 10 keV for the first time, but finds no evidence for an extended source or other off-nuclear point-sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power-law with a photon index {\Gamma} = 1.815 +/- 0.005 and a fluorescent Fe K{\alpha} line in good agreement with literature values. The spectrum does not require a high-energy exponential rollover, with a constraint of E_fold > 1 MeV. A thermal Comptonization continuum describes the data well, with parameters that agree with values measured by INTEGRAL, in particular an electron temperature kTe between ~100-300 keV, seed photon input temperatures between 5-50 eV. We do not find evidence for reflection or a broad iron line and put stringent upper limits of R < 0.01 on the reflection fraction and accretion disk illumination. We use archival Chandra data to estimate the contribution from diffuse emission, extra-nuclear point-sources, and the outer X-ray jet to the observed NuSTAR and XMM-Newton X-ray spectra and find the contribution to be negligible. We discuss different scenarios for the physical origin of the observed hard X-ray spectrum, and conclude that the inner disk is replaced by an advection-dominated accretion flow or that the X-rays are dominated by synchrotron self-Compton emission from the inner regions of the radio jet or a combination thereof., Comment: 13 pages, 6 figures, accepted for publication in ApJ

Active galactic nuclei (AGNs) show a correlation between the size of the broad line region (BLR) and the monochromatic continuum luminosity at 5100 \AA, allowing black hole mass estimation based on single-epoch spectra. However, the validity of the correlation is yet to be clearly tested for high-luminosity AGNs. We present the first reverberation-mapping results of the Seoul National University AGN monitoring program (SAMP), which is designed to focus on luminous AGNs for probing the high end of the size-luminosity relation. We report time lag measurements of two AGNs, namely, 2MASS J10261389+5237510 and SDSS J161911.24+501109.2, using the light curves obtained over a $\sim$1000 day period with an average cadence of $\sim$10 and $\sim$20 days, respectively for photometry and spectroscopy monitoring. Based on a cross-correlation analysis and H$\beta$ line width measurements, we determine the H$\beta$ lag as $41.8^{+4.9}_{-6.0}$ and $52.6^{+17.6}_{-14.7}$ days in the observed-frame, and black hole mass as $3.65^{+0.49}_{-0.57} \times 10^7 M_{\odot}$ and $23.02^{+7.81}_{-6.56} \times 10^7 M_{\odot}$, respectively for 2MASS J1026 and SDSS J1619., Comment: 14 pages; accepted by ApJ

We investigate the performance of different methodologies that measure the time lag between broad-line and continuum variations in reverberation mapping data using simulated light curves that probe a range of cadence, time baseline, and signal-to-noise ratio in the flux measurements. We compare three widely-adopted lag measuring methods: the Interpolated Cross-Correlation Function (ICCF), the z-transformed Discrete Correlation Function (ZDCF) and the MCMC code JAVELIN, for mock data with qualities typical of multi-object spectroscopic reverberation mapping (MOS-RM) surveys that simultaneously monitor hundreds of quasars. We quantify the overall lag detection efficiency, the rate of false detections, and the quality of lag measurements for each of these methods and under different survey designs (e.g., observing cadence and depth) using mock quasar light curves. Overall JAVELIN and ICCF outperform ZDCF in essentially all tests performed. Compared with ICCF, JAVELIN produces higher quality lag measurements, is capable of measuring more lags with timescales shorter than the observing cadence, is less susceptible to seasonal gaps and S/N degradation in the light curves, and produces more accurate lag uncertainties. We measure the Hbeta broad-line region size-luminosity (R-L) relation with each method using the simulated light curves to assess the impact of selection effects of the design of MOS-RM surveys. The slope of the R-L relation measured by JAVELIN is the least biased among the three methods, and is consistent across different survey designs. These results demonstrate a clear preference for JAVELIN over the other two non-parametric methods for MOS-RM programs, particularly in the regime of limited light curve quality as expected from most MOS-RM programs., 22 pages, 34 figures, Accepted for publication in the Astrophysical Journal

We study the sudden optical and ultraviolet (UV) brightening of 1ES 1927+654, which until now was known as a narrow-line active galactic nucleus (AGN). 1ES 1927+654 was part of the small and peculiar class of "true Type-2" AGN, which lack broad emission lines and line-of-sight obscuration. Our high-cadence spectroscopic monitoring captures the appearance of a blue, featureless continuum, followed several weeks later by the appearance of broad Balmer emission lines. This timescale is generally consistent with the expected light travel time between the central engine and the broad-line emission region in (persistent) broad-line AGN. Hubble Space Telescope spectroscopy reveals no evidence for broad UV emission lines (e.g., CIV1549, CIII]1909, MgII2798), probably owing to dust in the broad-line emission region. To the best of our knowledge, this is the first case where the lag between the change in continuum and in broad-line emission of a "changing-look" AGN has been temporally resolved. The nature and timescales of the photometric and spectral evolution disfavor both a change in line-of-sight obscuration and a change of the overall rate of gas inflow as driving the drastic spectral transformations seen in this AGN. Although the peak luminosity and timescales are consistent with those of tidal disruption events seen in inactive galaxies, the spectral properties are not. The X-ray emission displays a markedly different behavior, with frequent flares on timescales of hours to days, and will be presented in a companion publication., accepted for publication in ApJ

We report 6 yr monitoring of a distant bright quasar CTS C30.10 (z = 0.90052) with the Southern African Large Telescope (SALT). We measured the rest-frame time-lag of $562\pm 2$ days between the continuum variations and the response of the Mg II emission line, using the Javelin approach. More conservative approach, based on five different methods, imply the time delay of $564^{+109}_{-71}$ days. This time delay, combined with other available measurements of Mg II line delay, mostly for lower redshift sources, shows that the Mg II line reverberation implies a radius-luminosity relation very similar to the one based on a more frequently studied H$\beta$ line., Comment: submitted to ApJ; comments welcome

Understanding the properties of the continuum radiation and broad emission lines of active galactic nuclei provide significant information not only to model the radiation mechanism and constrain the geometry and kinematics of the broad-line region (BLR) but also to probe the central engine of the sources. Here we investigate the multifractal behaviour of the H$\beta$ emission line and the 5100 {\AA} continuum flux light curves of NGC 5548. The aim is to search for multi-scaling signatures in the light curves and check if there is a possible nonlinear relationship between them. To this end, we use a multifractality analysis technique called Multifractal Detrended Moving Average (MFDMA) analysis. We detect multifractal (nonlinear) signatures in the full monitoring and densely sampled period of the H$\beta$ line and 5100 {\AA} continuum light curves of NGC 5548, possibly indicating the presence of complex and nonlinear interaction in the 5100 {\AA} continuum and H$\beta$ emission line regions. Moreover, the degree of multifractality of H$\beta$ line is found to be about twice that of the 5100 {\AA} continuum. The nonlinearity of both emissions could be generated when the broad-line region reprocesses the radiation from the central compact source. Finally, we found that anti-persistent long-range temporal correlation is the main source of the multifractality detected in both light curves., Comment: 15 pages, 8 figures, accepted for publication in the Astrophysical journal

Giant Radio Galaxies (GRG) are the largest single entities in the Universe, having a projected linear size exceeding 0.7 Mpc, which implies that they are also quite old objects. They are not common, representing a fraction of only about 6% in samples of bright radio galaxies. While a census of about 300 of these objects has been built in the past years, still no light has been shed on the conditions necessary to allow such an exceptional growth, whether of environmental nature or linked to the inner accretion properties. Recent studies found that samples of radio galaxies selected from hard X-ray AGN catalogs selected from INTEGRAL/IBIS and Swift/BAT (thus at energies >20 keV) present a fraction of GRG four times larger than what found in radio-selected samples. We present radio observations of 15 nuclei of hard X-ray selected GRG, finding for the first time a large fraction (61%) of young radio sources at the center of Mpc-scale structures. Being at the center of GRG, these young nuclei may be undergoing a restarting activity episode, suggesting a link between the detected hard X-ray emission - due to the ongoing accretion - and the reactivation of the jets., Accepted for publication on ApJ

We present the results of the first X-ray study of a sample of 16 young radio sources classified as Compact Symmetric Objects (CSOs). We observed six of them for the first time in X-rays using {\it Chandra}, re-observed four with the previous {\it XMM-Newton} or {\it Beppo-SAX} data, and included six other with the archival data. All the sources are nearby, $z, to be published in the Astrophysical Journal

We report results from the observations of the well studied TeV blazar Mrk 421 with the Swift and the Suzaku satellites in December 2008. During the observation, Mrk 421 was found in a relatively low activity state, with the corresponding 2-10 keV flux of $3 \times 10^{-10}$ erg/s/cm^2. For the purpose of robust constraining the UV-to-X-ray emission continuum we selected only the data corresponding to truly simultaneous time intervals between Swift and Suzaku, allowing us to obtain a good-quality, broad-band spectrum despite a modest length (0.6 ksec) exposure. We analyzed the spectrum with the parametric forward-fitting SYNCHROTRON model implemented in XSPEC assuming two different representations of the underlying electron energy distribution, both well motivated by the current particle acceleration models: a power-law distribution above the minimum energy $\gamma_{\rm min}$ with an exponential cutoff at the maximum energy $\gamma_{\rm max}$, and a modified ultra-relativistic Maxwellian with an equilibrium energy $\gamma_{\rm eq}$. We found that the latter implies unlikely physical conditions within the blazar zone of Mrk 421. On the other hand, the exponentially moderated power-law electron distribution gives two possible sets of the model parameters: (i) flat spectrum $dN'_e/d\gamma \propto \gamma^{-1.91}$ with low minimum electron energy $\gamma_{\rm min}, Comment: 18 pages, 2 figures; accepted for publication in the Astrophysical Journal

We analyze the linear polarization of the relativistic jet in BL Lacertae object OJ 287 as revealed by multi-epoch Very Long Baseline Array images at 43 GHz and monitoring observations at optical bands. The electric-vector position angle of the optical polarization matches that at 43 GHz at locations that are often in the compact millimeter-wave >core> or, at other epochs, coincident with a bright, quasi-stationary emission feature ∼0.2 mas (∼0.9 pc projected on the sky) downstream from the core. This implies that electrons with high enough energies to emit optical synchrotron and γ-ray inverse Compton radiation are accelerated both in the core and at the downstream feature, the latter of which lies ≥10 pc from the central engine. The polarization vector in the stationary feature is nearly parallel to the jet axis, as expected for a conical standing shock capable of accelerating electrons to GeV energies.© 2018. The American Astronomical Society. All rights reserved.., The authors thank Dr. Ioannis Myserlis for a critical review of a draft of this manuscript. The authors acknowledge financial support by MEXT/JSPS Grant-in-Aid for Scientific Research on Innovative Areas (No. 25120007). M.S. was supported during this study by a JSPS Postdoctoral Fellowship for Research Abroad. The research at Boston University was supported in part by National Science Foundation grant AST-1615796 and NASA Fermi Guest Investigator Program grants NNX14AQ58G and 80NSSC17K0649. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia y Competitividad (MINECO) of Spain. The research at the IAA-CSIC was supported in part by the MINECO through grants AYA2016-80889-P, AYA2013-40825-P, and AYA2010-14844; and by the regional government of Andalucia through grant P09-FQM-4784. Calar Alto Observatory is jointly operated by the Max-Planck-Institut fur Astronomie and the IAA-CSIC. The VLBA is an instrument of the Long Baseline Observatory (LBO). The LBO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Data from the Steward Observatory spectro-polarimetric monitoring project were used. This program was supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G.

We present the rest-frame UV and optical photometry and morphology of low-redshift broad-line quasar host galaxies from the Sloan Digital Sky Survey Reverberation Mapping project. Our sample consists of 103 quasars at $z, Comment: 21 pages, 20 figures, accepted by ApJ

We present combined $\approx 14-37~\rm ks$ Chandra observations of seven $z = 1.6-2.7$ broad absorption line (BAL) quasars selected from the Large Bright Quasar Survey (LBQS). These seven objects are high-ionization BAL (HiBAL) quasars, and they were undetected in the Chandra hard band ($2-8$ keV) in previous observations. The stacking analyses of previous Chandra observations suggested that these seven objects likely contain some candidates for intrinsically X-ray weak BAL quasars. With the new Chandra observations, six targets are detected. We calculate their effective power-law photon indices and hard-band flux weakness, and find that two objects, LBQS $1203+1530$ and LBQS $1442-0011$, show soft/steep spectral shapes ($\Gamma_{\rm eff}= 2.2^{+0.9}_{-0.9}$ and $1.9_{-0.8}^{+0.9}$) and significant X-ray weakness in the hard band (by factors of $\approx$ 15 and 12). We conclude that the two HiBAL quasars are good candidates for intrinsically X-ray weak BAL quasars. The mid-infrared-to-UV spectral energy distributions (SEDs) of the two candidates are consistent with those of typical quasars. We constrain the fraction of intrinsically X-ray weak AGNs among HiBAL quasars to be $\approx 7-10\%$ ($2/29-3/29$), and we estimate it is $\approx 6- 23\%$ ($2/35-8/35$) among the general BAL quasar population. Such a fraction is considerably larger than the fraction among non-BAL quasars, and we suggest that intrinsically X-ray weak quasars are preferentially observed as BAL quasars. Intrinsically X-ray weak AGNs likely comprise a small minority of the luminous type 1 AGN population, and they should not affect significantly the completeness of these AGNs found in deep X-ray surveys., Comment: 11 pages, 6 figures, accepted for publication in ApJ

著者人数：174名, Accepted: 2010-04-10, 資料番号: SA1002620000

In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the spectral energy distribution (SED) of GPS sources with their expansion, predicting significant and complex high-energy emission, from the X-ray to the gamma-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N_H) and radio (N_HI) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes., Comment: 29 pages, 3 figures, 6 tables; to appear in ApJ. A few clarifications included, according to referee's suggestions

We use a suite of semi-empirical models to predict galaxy merger rates and contributions to bulge growth as functions of merger mass, redshift, and mass ratio. The models use empirical halo occupation constraints to identify mergers, together with high-resolution simulations to quantify how mergers with different properties contribute to the bulge population. We find good agreement with a variety of observational constraints, and provide fitting functions for merger rates and contributions to bulge growth. We identify several robust conclusions. (1) Major mergers dominate formation and assembly of L* bulges and the spheroid mass density, minor mergers contribute ~30%. (2) This is mass-dependent: bulge formation is dominated by more minor mergers in lower-mass systems. At higher masses, bulges form in major mergers near L*, but subsequently assemble in minor mergers. (3) The minor/major contribution is also morphology-dependent: higher B/T systems form in more major mergers, lower B/T systems form in situ from minor mergers. (4) Low-mass galaxies, being gas-rich, require more major mergers to reach the same B/T as high-mass systems. (5) Absolute merger rates increase with galaxy mass. (6) Predicted rates agree well with observations, but suggest that some morphology-selected samples include contamination from minor mergers. (7) Predicted rates agree with integrated growth in bulge mass with cosmic time, but with factor ~2 uncertainty - half the bulge mass density could come from non-mergers. We consider ~1000 model variations and quantify resulting uncertainties. Conclusions regarding the major/minor contribution to bulge growth are very robust, absolute merger rates have systematic factor ~2 uncertainties., Comment: 18 figures, 29 pages. Accepted for publication in ApJ. A script to provide predicted galaxy merger rates is available at http://www.cfa.harvard.edu/~phopkins/Site/mergercalc.html

A Chandra X-ray imaging observation of the jet in Pictor A showed a feature that appears to be a flare that faded between 2000 and 2002. The feature was not detected in a follow-up observation in 2009. The jet itself is over 150 kpc long and a kpc wide, so finding year-long variability is surprising. Assuming a synchrotron origin of the observed high-energy photons and a minimum energy condition for the outflow, the synchrotron loss time of the X-ray emitting electrons is of order 1200 yr, which is much longer than the observed variability timescale. This leads to the possibility that the variable X-ray emission arises from a very small sub-volume of the jet, characterized by magnetic field that is substantially larger than the average over the jet., 12 pages, 3 figures, to appear in Ap. J. Letters

We present Chandra X-ray imaging of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like structure. X-rays are detected from 59% of 56 jets. No counterjets were detected. The core spectra are fitted by power law spectra with photon index $\Gamma_x$ whose distribution is consistent with a normal distribution with mean 1.61{+0.04}{-0.05} and dispersion 0.15{+0.04}{-0.03}. We show that the distribution of $\alpha_{rx}$, the spectral index between the X-ray and radio band jet fluxes, fits a Gaussian with mean 0.974 $\pm$ 0.012 and dispersion 0.077 $\pm$ 0.008. We test the model in which kpc-scale X-rays result from inverse Compton scattering of cosmic microwave background photons off the jet's relativistic electrons (the IC-CMB model). In the IC-CMB model, a quantity Q computed from observed fluxes and the apparent size of the emission region depends on redshift as $(1+z)^{3+\alpha}$. We fit $Q \propto (1+z)^{a}$, finding $a = 0.88 \pm 0.90$ and reject at 99.5% confidence the hypothesis that the average $\alpha_{rx}$ depends on redshift in the manner expected in the IC-CMB model. This conclusion is mitigated by lack of detailed knowledge of the emission region geometry, which requires deeper or higher resolution X-ray observations. Furthermore, if the IC-CMB model is valid for X-ray emission from kpc-scale jets, then the jets must decelerate on average: bulk Lorentz factors should drop from about 15 to 2-3 between pc and kpc scales. Our results compound the problems that the IC-CMB model has in explaining the X-ray emission of kpc-scale jets., Comment: 41 pages, 15 figures, accepted for publication in the Astrophysical Journal Supplements

We present the X-ray properties of the 'Teacup AGN' (SDSS J1430+1339), a $z=0.085$ type 2 quasar which is interacting dramatically with its host galaxy. Spectral modelling of the central quasar reveals a powerful, highly obscured AGN with a column density of $N_{\rm H}=(4.2$-$6.5)\times 10^{23}$ cm$^{-2}$ and an intrinsic luminosity of $L_{\rm 2\mbox{-}10\,keV}=(0.8$-$1.4)\times 10^{44}$ erg s$^{-1}$. The current high bolometric luminosity inferred ($L_{\rm bol}\approx 10^{45}$-$10^{46}$ erg s$^{-1}$) has ramifications for previous interpretations of the Teacup as a fading/dying quasar. High resolution Chandra imaging data reveal a $\approx 10$ kpc loop of X-ray emission, co-spatial with the 'eastern bubble' previously identified in luminous radio and ionised gas (e.g., [OIII] line) emission. The X-ray emission from this structure is in good agreement with a shocked thermal gas, with $T=(4$-$8)\times 10^{6}$ K, and there is evidence for an additional hot component with $T\gtrsim 3\times 10^{7}$ K. Although the Teacup is a radiatively dominated AGN, the estimated ratio between the bubble power and the X-ray luminosity is in remarkable agreement with observations of ellipticals, groups, and clusters of galaxies undergoing AGN feedback., 8 pages, 4 figures, 1 table; Accepted for publication in ApJL

In late 2016 and early 2017 the flat spectrum radio quasar CTA 102 exhibited a very strong and long-lasting outburst. The event can be described by a roughly 2 months long increase of the baseline flux in the monitored energy bands (optical to $\gamma$ rays) by a factor 8, and a subsequent decrease over another 2 months back to pre-flare levels. The long-term trend was superseded by short but very strong flares, resulting in a peak flux that was a factor 50 above pre-flare levels in the $\gamma$-ray domain and almost a factor 100 above pre-flare levels in the optical domain. In this paper we explain the long-term evolution of the outburst by the ablation of a gas cloud penetrating the relativistic jet. The slice-by-slice ablation results in a gradual increase of the particle injection until the center of the cloud is reached, after which the injected number of particles decreases again. With reasonable cloud parameters we obtain excellent fits of the long-term trend., Comment: 9 pages, 5 figures; accepted for publication in The Astrophysical Journal

Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy (gamma-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad line-region, or dusty molecular torus. The lack or weakness of bulk Compton and Klein-Nishina features indicated by the presently available data favors production of gamma-rays via up-scattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical and gamma-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intra-day flares occasionally observed in powerful blazars sources., Comment: 34 pages, accepted for publication in the Astrophysical Journal

We report X-ray imaging of the powerful FR-II radio galaxy 3C353 using the Chandra X-ray Observatory. 3C353's two 4"-wide and 2'-long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR-II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem., Comment: 17 pages, 12 figures, accepted for publication in ApJ. Full resolution paper is available from http://www.hp.phys.titech.ac.jp/kataoka/paper/3C353_accepted.pdf

Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes' electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern gamma-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.

We report the discovery of the largest giant radio galaxy, J1420-0545: a FR type II radio source with an angular size of 17.4' identified with an optical galaxy at z=0.3067. Thus, the projected linear size of the radio structure is 4.69 Mpc (if we assume that H_{0}=71 km\s\Mpc, Omega_{m}=0.27, and Omega_{\Lambda}=0.73). This makes it larger than 3C236, which is the largest double radio source known to date. New radio observations with the 100 m Effelsberg telescope and the Giant Metrewave Radio Telescope, as well as optical identification with a host galaxy and its optical spectroscopy with the William Herschel Telescope are reported. The spectrum of J1420-0545 is typical of elliptical galaxies in which continuum emission with the characteristic 4000A discontinuity and the H and K absorption lines are dominated by evolved stars. The dynamical age of the source, its jets' power, the energy density, and the equipartition magnetic field are calculated and compared with the corresponding parameters of other giant and normal-sized radio galaxies from a comparison sample. The source is characterized by the exceptionally low density of the surrounding IGM and an unexpectedly high expansion speed of the source along the jet axis. All of these may suggest a large inhomogeneity of the IGM., Comment: 20 pages, 5 figures, 3 tables

We have used GMOS-IFU and high resolution HST-ACS observations to map, in unprecedented detail, the gas velocity field and structure within the 0.7 kpc circumnuclear ring of the SBb LINER/Seyfert 1 galaxy NGC 1097. We find clear evidence of radial streaming motions associated with spiral structures leading to the unresolved (, 4 pages, 3 figures using emulateapj. Accepted for publication in Astrophysical Journal Letters. Download high-resolution version from http://www.astro.uu.se/~kambiz/DOC/paper-N1097.pdf

In this work we studied the two-dimensional ionization structure of the circumnuclear and extranuclear regions in a sample of six low-z ultraluminous infrared galaxies using integral field spectroscopy. The ionization conditions in the extranuclear regions of these galaxies (∼5-15 kpc) are typical of LINERs as obtained from the Veilleux-Osterbrock line ratio diagnostic diagrams. The range of observed line ratios is best explained by the presence of fast shocks with velocities of 150-500 km s-1, while ionization by an AGN or nuclear starburst is in general less likely. The comparison of the two-dimensional ionization level and velocity dispersion in the extranuclear regions of these galaxies shows a positive correlation, further supporting the idea that shocks are indeed the main cause of ionization. The origin of these shocks is also investigated. Despite the likely presence of superwinds in the circumnuclear regions of these systems, no evidence for signatures of superwinds such as double velocity components is found in the extended extranuclear regions. We consider a more likely explanation for the presence of shocks, the existence of tidally induced large-scale gas flows caused by the merging process itself, as evidenced by the observed velocity fields characterized by peak-to-peak velocities of 400 km s-1 and velocity dispersions of up to 200 km s-1. © 2006. The American Astronomical Society. All rights reserved., A. M.-I. acknowledges support from the Euro3D Research Training Network, funded by the EC (HPRN-CT-2002-00305). Financial support was provided by the Spanish Ministry for Education and Science through grant AYA2002-01055.

The kinematic properties of the gaseous and stellar components of 11 ultraluminous infrared galaxies (ULIRGs; 14 nuclei) are investigated by means of integral field spectroscopy (IFS) with the INTEGRAL system and available IR and CO millimeter spectroscopy. The sample of ULIRGs cover different phases of the merging process and span all levels of activity from pure starbursts to Seyfert nuclei. The IFS data show that the ionized gas has a complex velocity structure with peak-to-peak velocity differences of a few to several hundred km s-1, detected in tidal tails or extranuclear star-forming regions. The velocity field of the ionized gas on scales of a few to several kiloparsecs is dominated by tidally induced flows and does not, in general, correspond to rotationally supported systems with a privileged orientation along the major rotating axis. The central velocity amplitude of the ionized gas and stars shows discrepancies in some galaxies but has, on average, a similar value (ratio of 0.92 ∓ 0.37), while the velocity amplitude of the molecular gas is a factor of 2 larger (ratio of 1.9 ∓ 0.6) than that of the stars and ionized gas. The central velocity amplitude measured using different kinematic tracers should therefore not be used in ULIRGs as a reliable tracer of mass, in general. The IFS data also show that the velocity dispersion of the ionized gas maps the large-scale motions associated with tidal tails and extranuclear regions, with often the highest velocity dispersion not being associated with the nucleus galaxies. There is, however, a good agreement between the central ionized gas and stellar velocity dispersions (ratio of 1.01 ∓ 0.13), while the cold molecular gas velocity dispersion has lower values (average of about 0.8 that of the stellar and ionized gas). The central ionized gas velocity dispersion is therefore a robust and homogeneous observable and a good tracer of the dynamical mass in these systems. The IFS-based central ionized gas velocity dispersion measurements confirm that ULIRGs' hosts are moderate-mass (≤m*) galaxies, as previously concluded by Tacconi and coworkers. In general, velocity amplitudes should not be used to estimate the dynamical mass in high-z star-forming systems, such as Lyman break and in particular submillimeter galaxies, since they show irregular stellar and gaseous structures similar to those present in low-z merging systems such as ULIRGs, the subject of this study. A more reliable method is to measure the central velocity dispersion using the strong, high equivalent width, rest-frame optical emission lines, provided the location of the nucleus is independently established by high angular resolution red or near-IR rest-frame imaging. The kinematics derived from the millimeter CO line suggest that the cold gas in ULIRGs does not share the velocity field of the stars and ionized gas and seems to be more rotationally supported. This result needs to be investigated in more detail with a larger sample of low-z ULIRGs before using the millimeter CO line widths as a dynamical mass tracer in high-z submillimeter galaxies. © 2005. The American Astronomical Society. All rights reserved., Financial support for this work was provided by the Spanish Ministry for Science and Technology through grant AYA2002-01055

Integral field optical spectroscopy with the INTEGRAL system has been used to investigate for the first time the two-dimensional kinematic and ionization properties of the extended, warm, ionized gas in Arp 220 over an area of 75″.0 × 40″.0 (i.e., 28 × 15 kpc). The structure of the ionized gas is divided into well-identified regions associated with the X-ray - emitting plumes and extended lobes, previously studied in detail by McDowell and collaborators. The overall ionization state of the warm gas in the plumes and lobes, as traced by the [N II]/Hα line, is consistent with high-velocity shocks expanding in a neutral ambient medium. Changes in the ionization state of the gas along the major axis of the plumes are detected, in particular in the outer regions of the northwestern plume, where the transition between the main stellar body of the galaxy and a broad, low surface brightness tidal tail is located. If the plumes are produced by a starburst-driven galactic wind, the efficiency in the conversion of mechanical to radiation energy is a factor of at least 10 smaller than in galactic winds developed in edge-on spiral galaxies with well-defined rotation and axis of outflow. The kinematic properties of the lobes, with an average velocity of +8 km s-1 (east lobe) and -79 km s-1 (west lobe), are to a first order in agreement with the predictions of the merger scenario, according to which the lobes are tidally induced gas condensations produced during the merging process. The largest velocity gradients of 50 km s-1 kpc-1 and velocity deviations of up to +280 and -320 km s-1 from the systemic velocity are associated not with the plumes but with the outer stellar envelope and broad tidal tails at distances of up to 7.5 kpc, indicating that the large-scale kinematics of the extended ionized gas in Arp 220 is most likely dominated by the tidally induced motions, and not by galactic winds associated with nuclear starbursts., Luis Colina thanks the Instituto de Astrofísica de Canarias and the Space Telescope Science Institute for their hospitality and financial support. We also thank Luis Cuesta for his help using GRAFICOS. Support for this work was provided by CICYT (Comisión Interministerial de Ciencia y Tecnología), through grants PB98-0340-C01, PB98-0340-C02, and AYA2002-01055. Dave Clements acknowledges funding by PPARC.

In this paper, we test the possibility that the structure of the largest radio galaxy J1420-0545 may have been formed by restarted rather than primary jet activity. This hypothesis was motivated by the unusual morphological properties of the source consisting of two edge-brightened, narrow, highly collinear, and symmetric lobes, thus suggesting an almost ballistic propagation of powerful jets into a particularly low-density external medium. New observations made with the VLA together with the currently available GLEAM and TGSS ADR1 data releases allow the detection of an excess emission at low frequencies. An extracted part (88 MHz - 200 MHz) of the spectrum of the emission is fitted with the DYNAGE model, giving a forecast for the environmental conditions and the energetic requirements for the presumed old cocoon related to a preceding epoch of jet activity., 8 pages, 3 figures, 3 tables

During the Space Telescope and Optical Reverberation Mapping Project (STORM) observations of NGC 5548, the continuum and emission-line variability became de-correlated during the second half of the 6-month long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as a part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than being due to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all the three observations: the UV emission line flux decrease, the soft-excess increase, and the emission line anomaly., ApJ in press. Replaced with the accepted version

We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analysis of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range 9 < log M_{stellar}/M_{\odot} < 12 with uncertainties of ~0.19 dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M_{stellar} and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z>3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs., 12 pages, 6 figures, Accepted for publication in ApJ

We present a radio-quiet quasar at z=0.237 discovered "turning on" by the intermediate Palomar Transient Factory (iPTF). The transient, iPTF 16bco, was detected by iPTF in the nucleus of a galaxy with an archival SDSS spectrum with weak narrow-line emission characteristic of a low-ionization emission line region (LINER). Our follow-up spectra show the dramatic appearance of broad Balmer lines and a power-law continuum characteristic of a luminous (L_bol~10^45 erg/s) type 1 quasar 12 years later. Our photometric monitoring with PTF from 2009-2012, and serendipitous X-ray observations from the XMM-Newton Slew Survey in 2011 and 2015, constrain the change of state to have occurred less than 500 days before the iPTF detection. An enhanced broad Halpha to [OIII]5007 line ratio in the type 1 state relative to other changing-look quasars also is suggestive of the most rapid change of state yet observed in a quasar. We argue that the >10 increase in Eddington ratio inferred from the brightening in UV and X-ray continuum flux is more likely due to an intrinsic change in the accretion rate of a pre-existing accretion disk, than an external mechanism such as variable obscuration, microlensing, or the tidal disruption of a star. However, further monitoring will be helpful in better constraining the mechanism driving this change of state. The rapid "turn on" of the quasar is much shorter than the viscous infall timescale of an accretion disk, and requires a disk instability that can develop around a ~10^8 M_sun black hole on timescales less than a year., Accepted for Publication in ApJ

We present results on searches for point-like sources of neutrinos using four years of IceCube data, including the first year of data from the completed 86-string detector. The total livetime of the combined dataset is 1,373 days. For an E$^{-2}$ spectrum the median sensitivity at 90\% C.L. is $\sim 10^{-12}$ TeV$^{-1}$cm$^{-2}$s$^{-1}$ for energies between 1 TeV$-$1 PeV in the northern sky and $\sim 10^{-11}$ TeV$^{-1}$cm$^{-2}$s$^{-1}$ for energies between 100 TeV $-$ 100 PeV in the southern sky. The sensitivity has improved from both the additional year of data and the introduction of improved reconstructions compared to previous publications. In addition, we present the first results from an all-sky search for extended sources of neutrinos. We update results of searches for neutrino emission from stacked catalogs of sources, and test five new catalogs; two of Galactic supernova remnants and three of active galactic nuclei. In all cases, the data are compatible with the background-only hypothesis, and upper limits on the flux of muon neutrinos are reported for the sources considered., 36 pages, 15 figures. Submitted to the Astrophysical Journal

著者人数: 12名, Accepted: 2014-08-26, 資料番号: SA1140153000

We present two-dimensional spectroscopy of the 125 × 125 pc2 circumnuclear region of M31, obtained using two optical fiber systems, INTEGRAL and 2D-FIS, installed at the 4.2 m William Herschel Telescope at the Roque de los Muchachos Observatory on the island of La Palma, Spain. We present continuum and emission-line maps, emission-line quotients, and stellar and ionized gas velocity fields obtained under subarcsecond seeing conditions. We have discovered Hα, [O III] λλ4959, 5007, Hα, and [N II] λλ16548, 6584 emission in the inner 40 × 40 pc2 circumnuclear region. The intensity maps obtained from the emission lines show several isolated systems of ionized gas (clouds) a few parsecs in size. The kinematics of the clouds is decoupled from the stellar rotation, and strong radial motions are likely to be present. We have also discussed the ionization mechanisms present in the clouds. Although the emission-line quotients are compatible with ionization produced by post-asymptotic giant branch stars, the estimated ionization fluxes exceed what is expected according to the distribution of planetary nebulae in the bulge of M31. Comparison of the line quotients and spectra found in M31 with those found in the extended narrow-line region of the Seyfert galaxy NGC 4151 indicates that we could be in presence of ultralow-intensity nuclear activity. These results would be compatible with the existence of a >dead quasar> in the nucleus of M31 and underline the hybrid character of the LINER phenomenon., This work has been partially supported by the DGYCIT (PB98-0340).

We use long-slit spectroscopic data to study in detail the extended narrow-line regions (ENLRs) of the Seyfert 1 galaxy ESO 362-G18 and Seyfert 2 galaxy ESO 362-G8. These two galaxies have similar emission-line luminosities and extents of the ENLR (D4 kpc), whose shapes in previous narrowband (O III) images suggest anisotropic escape of the nuclear ionizing radiation as expected for shadowing by a nuclear torus in the framework of the uni—ed model. In the Seyfert 1 galaxy the high-excitation gas shows an approximately cone-shaped morphology. From the observed kinematics, we conclude that the gas within the cone most probably belongs to the galaxy disk, which implies that the collimation axis is closer to the disk than half the opening angle of the cone of ionizing radiation. In the Seyfert 2 galaxy, the main structure in the high-excitation gas is an emission blob which apparently consists of a high- latitude cloud being blown away from the nuclear region and ionized by the nuclear source. We use the radial distribution of stellar population features in order to extrapolate this population to the nucleus and isolate the optical continuum of the nuclear source. We obtain a featureless power-law continuum for the Seyfert 1 galaxy, while for the Seyfert 2 galaxy we conclude that the F l P l~0.76 nuclear bluer color and smaller equivalent widths of the absorption lines are due to an aging burst of star formation (age B 300 Myr) and that the nuclear source is hidden from direct view. Using the photoionization code MAPPINGS Ic and a mixture of matter-bounded (MB) and ionization-bounded (IB) clouds, we model the ENLRs of the two galaxies. We use all the observables, mostly the emission-line —uxes as a function of distance from the nucleus and the optical nuclear contin- uum observed in the Seyfert 1 galaxy as well as its X-ray —ux, to constrain the parameters of a self- consistent model for the ENLR. For both galaxies, we conclude that a power-law ionizing continuum better reproduces the high-excitation lines near the nucleus than a multisegmented power law F l P l~1.2 used in previous works. For the Seyfert 1 galaxy ESO 362-G18, the inferred luminosity of the ionizing continuum can be reconciled with the —ux observed in the optical, while in the X-rays the observed —ux is D100 times weaker than that necessary to reproduce the line —uxes, suggesting that the X-ray contin- uum is absorbed toward Earth. For the Seyfert 2 galaxy ESO 362-G8, the inferred ionizing continuum when extrapolated to the optical implies a minimum obscuration toward the nuclear source of A V B 4.0 mag. In the hypothesis of an isotropic nuclear source, in order to better constrain the model parameters, we have adopted symmetrical physical conditions as a function of distance on both sides of the nucleus: namely, the ionizing —ux, the temperature, density, and ionization parameter of the MB gas, and the metallicity. The radial density behavior of the IB gas was observationally inferred from the (S II) doublet ratio. The only free parameter, which was allowed to vary independently, was the relative proportion of the MB and IB emission-line components along the ENLR. The high-excitation gas within the cone of ESO 362-G18 and within the blob of ESO 362-G8 have been modeled as regions of larger mass contri- bution from the MB component relative to other locations of the ENLR. We derive the —lling factors, covering factors, and gas masses along the ENLR as a function of dis- tance from the nucleus. A comparison between the model results for the two galaxies shows that, around the nucleus, the Seyfert 1 galaxy has a larger excitation due to a larger contribution of the MB com- ponent. However, in the cone, the excitation is lower than in the blob of the Seyfert 2 galaxy due to a combination of a lower ionizing —ux and larger gas density in the disk of the Seyfert 1 galaxy. The total ionized gas mass derived for the blob in the Seyfert 2 galaxy is 105.8 consistent with its proposed M _ , origin in a nuclear superwind which probably occurred D300 Myr ago, while the ionized gas mass in the disk of the Seyfert 1 galaxy is 1 order of magnitude smaller. Subject headings: galaxies: activegalaxies: ISMgalaxies: nucleigalaxies: Seyfert

Integral field optical spectroscopy with the INTEGRAL fiber-based system is used to map the extended ionized regions and gas flows in Mrk 273, one of the closest ultraluminous infrared galaxies. The Hβ and [O III] λ5007 maps show the presence of two distinct regions separated by 4″ (3.1 kpc) along position angle (P.A.) 240°. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [O III] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [O III] ionized gas shows (1) the presence of highly disturbed gas in the regions around the LINER nucleus, (2) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 × 103 km s-1, and (3) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst and that the quiescent gas is directly ionized by a nuclear source, similar to the ionization cones typically seen in Seyfert galaxies., L. C. thanks the Instituto de Astrofísica de Canarias for its hospitality and financial support. K. D. B. thanks Raytheon for providing financial support during his sabbatical leave Support for this work was provided by NASA through grant GO06346.01-95A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

We present the detailed velocity field of the central 2 kpc of the LINER galaxy NGC 1672. The iso- velocity map shows a rotational pattern with a velocity gradient of 50 km s-ˡ arcsec-ˡ in the inner 6" (1"≈ 70 pc), indicating a mass of ≈ 9x 108 Mʘ inside a radius of 125 pc, equivalent to a density of ≈ 2 x 1011 Mʘ kpc-³. It also shows some asymmetries on a larger scale. An o†set of ≈ 60 pc between the nuclear continuum barycenter and the kinematical center is also found. Satoh"s model Ðtting to the observed velocity Ðeld reveals several nonaxisymmetric residuals, which do not correlate well with the bar or the circumnuclear ring of H II regions. The inner rotation curve of NGC 1672 reveals that the circumnuclear ring of star formation is located on an inner Lindblad resonance (ILR), and not near the peak of the Lindblad curve, Ω − (k/2), as suggested by previous works, which also claimed that the ring rotates faster than its ambient. This motion is not conÐrmed by the two-dimensional residual- velocity map.

We present the measurement of the projected and redshift space 2-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy AGN at 2.9$\leq$z$\leq$5.5 ($\langle L_{bol} \rangle \sim$10$^{46}$ erg/s) using the generalized clustering estimator based on phot-z probability distribution functions (Pdfs) in addition to any available spec-z. We model the projected 2pcf estimated using $\pi_{max}$ = 200 h$^{-1}$ Mpc with the 2-halo term and we derive a bias at z$\sim$3.4 equal to b = 6.6$^{+0.60}_{-0.55}$, which corresponds to a typical mass of the hosting halos of log M$_h$ = 12.83$^{+0.12}_{-0.11}$ h$^{-1}$ M$_{\odot}$. A similar bias is derived using the redshift-space 2pcf, modelled including the typical phot-z error $\sigma_z$ = 0.052 of our sample at z$\geq$2.9. Once we integrate the projected 2pcf up to $\pi_{max}$ = 200 h$^{-1}$ Mpc, the bias of XMM and \textit{Chandra} COSMOS at z=2.8 used in Allevato et al. (2014) is consistent with our results at higher redshift. The results suggest only a slight increase of the bias factor of COSMOS AGN at z$\gtrsim$3 with the typical hosting halo mass of moderate luminosity AGN almost constant with redshift and equal to logM$_h$ = 12.92$^{+0.13}_{-0.18}$ at z=2.8 and log M$_h$ = 12.83$^{+0.12}_{-0.11}$ at z$\sim$3.4, respectively. The observed redshift evolution of the bias of COSMOS AGN implies that moderate luminosity AGN still inhabit group-sized halos at z$\gtrsim$3, but slightly less massive than observed in different independent studies using X-ray AGN at z$\leq2$., Comment: Accepted for publication in The Astrophysical Journal

We report on the detection of excess hard X-ray emission from the TeV BL Lac object Mrk421 during the historical low-flux state of the source in January 2013. NuSTAR observations were conducted four times between MJD56294 and MJD56312 with a total exposure of 80.9 ksec. The source flux in the 3-40 keV range was nearly constant except for MJD56307, when the average flux level increased by a factor of three. Throughout the exposure, the X-ray spectra of Mrk421 were well represented by a steep power-law model with a photon index of 3.1, although a significant excess was noted above 20 keV in the MJD56302 data when the source was in its faintest state. Moreover, Mrk421 was detected at more than the 4-sigma level in the 40-79 keV count maps for both MJD56307 and MJD56302 but not during the remaining two observations. The detected excess hard X-ray emissions connect smoothly with the extrapolation of the high-energy gamma-ray continuum of the blazar constrained by Fermi-LAT during the source quiescence. These findings indicate that, while the overall X-ray spectrum of Mrk421 is dominated by the highest-energy tail of the synchrotron continuum, the variable excess hard X-ray emission above 20 keV (on the timescale of a week) is related to the inverse Compton emission component. We discuss the resulting constraints on the variability and spectral properties of the low-energy segment of the electron energy distribution in the source., 6 pages, 4 figures, accepted for publication in ApJ

Improving the capabilities of detecting faint X-ray sources is fundamental to increase the statistics on faint high-z AGN and star-forming galaxies. We performed a simultaneous Maximum Likelihood PSF fit in the [0.5-2] keV and [2-7] keV energy bands of the 4 Ms{\em Chandra} Deep Field South (CDFS) data at the position of the 34930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a raytracing simulation. We detected a total of 698 X-ray point-sources with a likelihood $\mathcal{L}$$>$4.98 (i.e. $>$2.7$��$). We show that the prior knowledge of a deep sample of Optical-NIR galaxies leads to a significant increase of the detection of faint (i.e. $\sim$10$^{-17}$ cgs in the [0.5-2] keV band) sources with respect to "blind" X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely star-forming galaxies or faint absorbed AGN. We identified a few sources sources with putative photometric redshift z$>$4. Despite the low number statistics and the uncertainties on the photo-z, this sample significantly increases the number of X--ray selected candidate high-z AGN., 15 Pages, 10 Figures, Accepted by ApJ, version before editing, Catalog available at: http://www.astrodeep.eu/chandra-counterparts/ , CDS and www.astrodeep.edu

Accepted: 2015-12-15, 資料番号: SA1150204000

著者人数: 177名, Accepted: 2012-03-28, 資料番号: SA1004162000

The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5 {\sigma} using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability time scale is estimated to be 6.4 +/- 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy., Comment: Corresponding Authors: J. Becerra (josefa.becerra@nasa.gov), M. Nievas Rosillo (mnievas@ucm.es), M. Manganaro (manganaro@iac.es), F. Tavecchio (fabrizio.tavecchio@brera.inaf.it) Published in The Astrophysical Journal Letters (ApJL), 2015ApJ...815L..23A, DOI: 10.1088/2041-8205/815/2/L23

著者人数: 14名, Accepted: 2011-10-20, 資料番号: SA1003013000

The well studied blazar Markarian 421 (Mrk 421, $z$=0.031) was the subject of an intensive multi-wavelength campaign when it flared in 2013 April. The recorded X-ray and very high energy (VHE, E$>$100 GeV) $\gamma$-ray fluxes are the highest ever measured from this object. At the peak of the activity, it was monitored by the hard X-ray focusing telescope {\it Nuclear Spectroscopic Telescope Array} ({\it NuSTAR}) and {\it Swift} X-Ray Telescope (XRT). In this work, we present a detailed variability analysis of {\it NuSTAR} and {\it Swift}-XRT observations of Mrk 421 during this flaring episode. We obtained the shortest flux doubling time of 14.01$\pm$5.03 minutes, which is the shortest hard X-ray (3$-$79 keV) variability ever recorded from Mrk 421 and is on the order of the light crossing time of the black hole's event horizon. A pattern of extremely fast variability events superposed on slowly varying flares is found in most of the {\it NuSTAR} observations. We suggest that these peculiar variability patterns may be explained by magnetic energy dissipation and reconnection in a fast moving compact emission region within the jet. Based on the fast variability, we derive a lower limit on the magnetic field strength of $B \ge 0.73 \delta_1^{-2/3} \, \nu_{19}^{1/3}$~G, where $\delta_1$ is the Doppler factor in units of 10, and $\nu_{19}$ is the characteristic X-ray synchrotron frequency in units of $10^{19}$~Hz., Comment: 23 pages, 5 figures, 2 tables, to appear in the Astrophysical Journal

The astrophysical journal 807(1), 46 - (2015). doi:10.1088/0004-637X/807/1/46, In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates., Published by Univ.11032, Chicago, Ill. [u.a.]

arXiv:1502.05820v1.-- et al., We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1σ dispersion of 0.12 dex in luminosity and typical uncertainties of ∼0.19 in the spectral index and ∼0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies - currently inaccesible to ground-based observations - with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope. The decomposition code and templates are available at http://denebola.org/ahc/deblendIRS., A.H.-C. and A.A.-H. acknowledge funding by the Universidad de Cantabria Augusto González Linares programme and the Spanish Ministry of Economy and Competitiveness under grant AYA2012-31447, which is the party funded by the FEDER program. C.R.A. is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEFGA-2012-327934). T.D.S was supported by ALPIA-CONICYI grant number 31130005. S.F.H. acknowledges support from the Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (PIIF-GA-2013-623804). P.E. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2012-31277.

We present results from a fifteen-month campaign of high-cadence (~ 3 days) mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 $\mu$m and 4.5 $\mu$m flux variations lag behind those of the optical continuum by $37.2^{+2.4}_{-2.2}$ days and $47.1^{+3.1}_{-3.1}$ days, respectively. We report a cross-correlation time lag between the 4.5 $\mu$m and 3.6 $\mu$m flux of $13.9^{+0.5}_{-0.1}$ days. The lags indicate that the dust emitting at 3.6 $\mu$m and 4.5 $\mu$m is located at a distance of approximately 1 light-month (~ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ~ 2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGN. The 3.6 and 4.5 $\mu$m reverberation radii fall above the K-band $\tau \propto L^{0.5}$ size-luminosity relationship by factors $\lesssim 2.7$ and $\lesssim 3.4$, respectively, while the 4.5 $\mu$m reverberation radius is only 27% larger than the 3.6 $\mu$m radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range., Comment: 13 pages, 9 figures

Activity at the centers of galaxies, during which the central supermassive black hole is accreting material, is nowadays accepted to be rather ubiquitous and most probably a phase of every galaxy's evolution. It has been suggested that galactic mergers and interactions may be the culprits behind the triggering of nuclear activity. We use near-infrared data from the new Infrared Medium-Deep Survey (IMS) and the Deep eXtragalactic Survey (DXS) of the VIMOS-SA22 field and radio data at 1.4 GHz from the FIRST survey and a deep VLA survey to study the environments of radio-AGN over an area of ~25 sq. degrees and down to a radio flux limit of 0.1 mJy and a J-band magnitude of 23 mag AB. Radio-AGN are predominantly found in environments similar to those of control galaxies at similar redshift, J-band magnitude, and U-R rest-frame absolute color. However, a sub-population of radio-AGN is found in environments up to 100 times denser than their control sources. We thus preclude merging as the dominant triggering mechanism of radio-AGN. Through the fitting of the broadband spectral energy distribution of radio-AGN in the least and most dense environments, we find that those in the least dense environments show higher radio-loudness, higher star formation efficiencies, and higher accretion rates, typical of the so-called high-excitation radio-AGN. These differences tend to disappear at z>1. We interpret our results in terms of a different triggering mechanism for these sources that is driven by mass-loss through winds of young stars created during the observed ongoing star formation., 22 pages, 19 figures, accepted for publication in the ApJ