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Sample records for agn fraction increases

  1. Does the obscured AGN fraction really depend on luminosity?

    NASA Astrophysics Data System (ADS)

    Sazonov, S.; Churazov, E.; Krivonos, R.

    2015-12-01

    We use a sample of 151 local non-blazar active galactic nuclei (AGN) selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is mostly an intrinsic or selection effect. Using a torus-obscuration model, we demonstrate that in addition to negative bias, due to absorption in the torus, in finding obscured AGN in hard X-ray flux-limited surveys, there is also positive bias in finding unobscured AGN, due to Compton reflection in the torus. These biases can be even stronger taking into account plausible intrinsic collimation of hard X-ray emission along the axis of the obscuring torus. Given the AGN luminosity function, which steepens at high luminosities, these observational biases lead to a decreasing observed fraction of obscured AGN with increasing luminosity even if this fraction has no intrinsic luminosity dependence. We find that if the central hard X-ray source in AGN is isotropic, the intrinsic (i.e. corrected for biases) obscured AGN fraction still shows a declining trend with luminosity, although the intrinsic obscured fraction is significantly larger than the observed one: the actual fraction is larger than ˜85 per cent at L ≲ 1042.5 erg s-1 (17-60 keV), and decreases to ≲60 per cent at L ≳ 1044 erg s-1. In terms of the half-opening angle θ of an obscuring torus, this implies that θ ≲ 30° in lower luminosity AGN, and θ ≳ 45° in higher luminosity ones. If, however, the emission from the central supermassive black hole is collimated as dL/dΩ ∝ cos α, the intrinsic dependence of the obscured AGN fraction is consistent with a luminosity-independent torus half-opening angle θ ˜ 30°.

  2. The AGN Luminosity Fraction in Galaxy Mergers

    NASA Astrophysics Data System (ADS)

    Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

    2017-01-01

    Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  3. Fraction of the X-ray selected AGNs with optical emission lines in galaxy groups

    NASA Astrophysics Data System (ADS)

    Li, Feng; Yuan, Qirong; Bian, Weihao; Chen, Xi; Yan, Pengfei

    2017-04-01

    Compared with numerous X-ray dominant active galactic nuclei (AGNs) without emission-line signatures in their optical spectra, the X-ray selected AGNs with optical emission lines are probably still in the high-accretion phase of black hole growth. This paper presents an investigation on the fraction of these X-ray detected AGNs with optical emission-line spectra in 198 galaxy groups at z<1 in a rest frame 0.1-2.4 keV luminosity range 41.3 < log(LX/erg s^{-1}) < 44.1 within the Cosmological Evolution Survey (COSMOS) field, as well as its variations with redshift and group richness. For various selection criteria of member galaxies, the numbers of galaxies and the AGNs with optical emission lines in each galaxy group are obtained. It is found that, in total 198 X-ray groups, there are 27 AGNs detected in 26 groups. AGN fraction is on average less than 4.6 (±1.2)% for individual groups hosting at least one AGN. The corrected overall AGN fraction for whole group sample is less than 0.98 (±0.11) %. The normalized locations of group AGNs show that 15 AGNs are found to be located in group centers, including all 6 low-luminosity group AGNs (L_{ 0.5-2 keV} < 10^{42.5} erg s^{-1}). A week rising tendency with z are found: overall AGN fraction is 0.30-0.43% for the groups at z<0.5, and 0.55-0.64% at 0.5 < z < 1.0. For the X-ray groups at z>0.5, most member AGNs are X-ray bright, optically dull, which results in a lower AGN fractions at higher redshifts. The AGN fraction in isolated fields also exhibits a rising trend with redshift, and the slope is consistent with that in groups. The environment of galaxy groups seems to make no difference in detection probability of the AGNs with emission lines. Additionally, a larger AGN fractions are found in poorer groups, which implies that the AGNs in poor groups might still be in the high-accretion phase, whereas the AGN population in rich clusters is mostly in the low-accretion, X-ray dominant phase.

  4. The Role of Star Formation and AGN in Dust Heating of z=0.3-2.8 Galaxies - II. Informing IR AGN Fraction Estimates through Simulations

    NASA Astrophysics Data System (ADS)

    Roebuck, Eric; Sajina, Anna; Hayward, Christopher C.; Pope, Alexandra; Kirkpatrick, Allison; Hernquist, Lars; Yan, Lin

    2016-12-01

    A key question in extragalactic studies is the determination of the relative roles of stars and active galactic nuclei (AGNs) in powering dusty galaxies at z ˜ 1-3 where the bulk of star formation and AGN activity took place. In Paper I, we present a sample of 336 24 μm selected (Ultra)Luminous Infrared Galaxies, (U)LIRGs, at z˜ 0.3-2.8, where we focus on determining the AGN contribution to the IR luminosity. Here, we use hydrodynamic simulations with dust radiative transfer of isolated and merging galaxies to investigate how well the simulations reproduce our empirical IR AGN fraction estimates and determine how IR AGN fractions relate to the UV-mm AGN fraction. We find that: (1) IR AGN fraction estimates based on simulations are in qualitative agreement with the empirical values when host reprocessing of the AGN light is considered; (2) for star-forming galaxy (SFG)-AGN composites our empirical methods may be underestimating the role of AGN, as our simulations imply \\gt 50 % AGN fractions, ˜ 3× higher than previous estimates; (3) 6% of our empirically classified SFGs have AGN fractions ≳50%. While this is a small percentage of SFGs, if confirmed it would imply that the true number density of AGNs may be underestimated; (4) this comparison depends on the adopted AGN template—those that neglect the contribution of warm dust lower the empirical fractions by up to two times; and (5) the IR AGN fraction is only a good proxy for the intrinsic UV-mm AGN fraction when the extinction is high ({A}V≳ 1 or up to and including coalescence in a merger).

  5. An enhanced fraction of starbursting galaxies among high Eddington ratio AGNs

    NASA Astrophysics Data System (ADS)

    Bernhard, E.; Mullaney, J. R.; Daddi, E.; Ciesla, L.; Schreiber, C.

    2016-07-01

    We investigate the star-forming properties of 1620 X-ray selected active galactic nuclei (AGN) host galaxies as a function of their specific X-ray luminosity (i.e. X-ray luminosity per unit host stellar mass) - a proxy of the Eddington ratio. Our motivation is to determine whether there is any evidence of a suppression of star formation at high Eddington ratios, which may hint towards `AGN feedback' effects. Star formation rates (SFRs) are derived from fits to Herschel-measured far-infrared spectral energy distributions, taking into account any contamination from the AGN. Herschel-undetected AGNs are included via stacking analyses to provide average SFRs in bins of redshift and specific X-ray luminosity (spanning 0.01 lesssim L_X/M_{ast } lesssim 100 L_{{⊙}} M_{{⊙}}^{-1}). After normalizing for the effects of mass and redshift arising from the evolving galaxy main sequence, we find that the SFRs of high specific luminosity AGNs are slightly enhanced compared to their lower specific luminosity counterparts. This suggests that the SFR distribution of AGN hosts changes with specific X-ray luminosity, a result reinforced by our finding of a significantly higher fraction of starbursting hosts among high specific luminosity AGNs compared to that of the general star-forming galaxy population (i.e. 8-10 per cent versus 3 per cent). Contrary to our original motivation, our findings suggest that high specific luminosity AGNs are more likely to reside in galaxies with enhanced levels of star formation.

  6. THE CLUSTER AND FIELD GALAXY ACTIVE GALACTIC NUCLEUS FRACTION AT z = 1-1.5: EVIDENCE FOR A REVERSAL OF THE LOCAL ANTICORRELATION BETWEEN ENVIRONMENT AND AGN FRACTION

    SciTech Connect

    Martini, Paul; Miller, E. D.; Bautz, M.; Brodwin, M.; Stanford, S. A.; Gonzalez, Anthony H.; Hickox, R. C.; Stern, D.; Eisenhardt, P. R.; Galametz, A.; Norman, D.; Dey, A.; Jannuzi, B. T.; Murray, S.; Jones, C.; Brown, M. J. I.

    2013-05-01

    The fraction of cluster galaxies that host luminous active galactic nuclei (AGNs) is an important probe of AGN fueling processes, the cold interstellar medium at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M {>=} 10{sup 14} M{sub Sun }) at 1 < z < 1.5 selected from the Spitzer/IRAC Shallow Cluster Survey, as well as the field fraction in the immediate vicinity of these clusters, and combine these data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z {approx} 3. We estimate that the cluster AGN fraction at 1 < z < 1.5 is f{sub A} = 3.0{sup +2.4}{sub -1.4}% for AGNs with a rest-frame, hard X-ray luminosity greater than L{sub X,{sub H}} {>=} 10{sup 44} erg s{sup -1}. This fraction is measured relative to all cluster galaxies more luminous than M{sup *}{sub 3.6}(z) + 1, where M{sup *}{sub 3.6}(z) is the absolute magnitude of the break in the galaxy luminosity function at the cluster redshift in the IRAC 3.6 {mu}m bandpass. The cluster AGN fraction is 30 times greater than the 3{sigma} upper limit on the value for AGNs of similar luminosity at z {approx} 0.25, as well as more than an order of magnitude greater than the AGN fraction at z {approx} 0.75. AGNs with L{sub X,{sub H}} {>=} 10{sup 43} erg s{sup -1} exhibit similarly pronounced evolution with redshift. In contrast to the local universe, where the luminous AGN fraction is higher in the field than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1 < z < 1.5. This is evidence that the cluster AGN population has evolved more rapidly than the field population from z {approx} 1.5 to the present. This environment-dependent AGN evolution mimics the more rapid evolution of star-forming galaxies in clusters relative to the field.

  7. Constraining the fraction of Compton-thick AGN in the Universe by modelling the diffuse X-ray background spectrum

    NASA Astrophysics Data System (ADS)

    Akylas, A.; Georgakakis, A.; Georgantopoulos, I.; Brightman, M.; Nandra, K.

    2012-10-01

    This paper investigates which constraints can be placed on the fraction of Compton-thick active galactic nuclei (AGN) in the Universe from modelling the spectrum of the diffuse X-ray background (XRB). We present a model for the synthesis of the XRB that uses as input a library of AGN X-ray spectra generated by Monte Carlo simulations. This is essential to account for the Compton scattering of X-ray photons in a dense medium and the impact of that process on the spectra of heavily obscured AGN. We identify a small number of input parameters to the XRB synthesis code that encapsulate the minimum level of uncertainty in reconstructing the XRB spectrum. These are the power-law index and high-energy cutoff of the intrinsic X-ray spectra of AGN, the level of the reflection component in AGN spectra, and the fraction of Compton-thick AGN in the Universe. We then map the volume of the space allowed to these parameters by current observational determinations of the XRB spectrum in the range 3-100 keV. One of the least-constrained parameters is the fraction of Compton-thick AGN. Statistically acceptable fits to the XRB spectrum at the 68% confidence level can be obtained for Compton-thick AGN fractions in the range 5-50%. This is because of degeneracies among input parameters to the XRB synthesis code and uncertainties in the modelling of AGN spectra (e.g. level of reflection fraction). The most promising route for constraining the fraction of Compton-thick AGN in the Universe is via the direct detection of those sources in high-energy (≳ 10 keV) surveys. We show that the observed fraction of Compton-thick sources identified in the Swift/BAT serendipitous survey limits the intrinsic fraction of Compton-thick AGN, at least at low redshift, to 10-20% (68% confidence level). We also make predictions on the number density of Compton-thick sources that current and future X-ray missions are expected to discover. Testing those predictions with data will place tight constraints on

  8. The evolution of obscured AGN

    NASA Astrophysics Data System (ADS)

    Brightman, Murray

    2012-09-01

    We present results on the evolution of Compton thick AGN with redshift, and the nature of this obscuration, important for understanding the accretion history of the universe and for AGN unification schemes. We use lessons learned from spectral complexity of local AGN (Brightman & Nandra 2012) and up to date spectral models of heavily absorbed AGN, which take into account Compton scattering, self consistent Fe Ka modeling and the geometry of the circumnuclear material (Brightman & Nandra 2011), to optimise our identification of Compton thick AGN and understanding of the obscuring material. Results from the Chandra Deep Field South are presented (Brightman & Ueda, 2012), which show an increasing fraction of CTAGN with redshift and that most heavily obscured AGN are geometrically deeply buried in material, as well as new results from and extension of this study to AEGIS-XD and Chandra-COSMOS survey, which aim to fully characterise the dependence of heavy AGN obscuration on redshift and luminosity.

  9. A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

    NASA Technical Reports Server (NTRS)

    Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

    2014-01-01

    We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L(sub x)) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (gamma), hardness ratios, and L(sub X), in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L(sub X),0.5-8.0 keV > 10(exp 42) erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known alpha OX-?L? (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the 'non-AGN locus' in alpha OX-?L? (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR (is) less than -20 and L(sub X),0.5-8.0 keV (is) greater than 10(exp 41) erg s-1 is 0.08+0.35 -0.01, somewhat higher than the 5% fraction in galaxy clusters.

  10. AGN feedback in action? - outflows and star formation in type 2 AGNs

    NASA Astrophysics Data System (ADS)

    Woo, Jong-Hak

    2017-01-01

    We present the statistical constraints on the ionized gas outflows and their connection to star formation, using a large sample of ~110,000 AGNs and star-forming galaxies at z < 0.3. First, we find a dramatic difference of the outflow signatures between AGNs and star-forming galaxies based on the [OIII] emission line kinematics. While the [OIII] velocity and velocity dispersion of star forming galaxies can be entirely accounted by the gravitational potential of host galaxies, AGNs clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. Second, the distribution in the [OIII] velocity - velocity dispersion diagram dramatically expands toward large values with increasing AGN luminosity, implying that the outflows are AGN-driven. Third, the fraction of AGNs with a signature of outflow kinematics, steeply increases with AGN luminosity and Eddington ratio. In particular, the majority of luminous AGNs presents strong non-gravitational kinematics in the [OIII] profile. Interestingly, we find that the specific star formation of non-outflow AGNs is much lower than that of strong outflow AGNs, while the star formation rate of strong outflow AGNs is comparable to that of star forming galaxies. We interpret this trend as a delayed AGN feedback as it takes dynamical time for the outflows to suppress star formation in galactic scales.

  11. A New Catalog of Type 1 AGNs and its Implications on the AGN Unified Model

    NASA Astrophysics Data System (ADS)

    Oh, Kyuseok; Yi, Sukyoung K.; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Soto, Kurt

    2015-07-01

    We have recently identified a substantial number of type 1 active galactic nuclei (AGNs) featuring weak broad-line regions (BLRs) at z\\lt 0.2 from detailed analysis of galaxy spectra in the Sloan Digital Sky Survey Data Release 7. These objects predominantly show a stellar continuum but also a broad Hα emission line, indicating the presence of a low-luminosity AGN oriented so that we are viewing the central engine directly without significant obscuration. These accreting black holes have previously eluded detection due to their weak nature. The newly discovered BLR AGNs have increased the number of known type 1 AGNs by 49%. Some of these new BLR AGNs were detected with the Chandra X-ray Observatory, and their X-ray properties confirm that they are indeed type 1 AGNs. Based on our new and more complete catalog of type 1 AGNs, we derived the type 1 fraction of AGNs as a function of [O iii] λ 5007 emission luminosity and explored the possible dilution effect on obscured AGNs due to star formation. The new type 1 AGN fraction shows much more complex behavior with respect to black hole mass and bolometric luminosity than has been suggested previously by the existing receding torus model. The type 1 AGN fraction is sensitive to both of these factors, and there seems to be a sweet spot (ridge) in the diagram of black hole mass and bolometric luminosity. Furthermore, we present the possibility that the Eddington ratio plays a role in determining opening angles.

  12. The BAT AGN Spectroscopic Survey (BASS)

    NASA Astrophysics Data System (ADS)

    Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Balokovic, Mislav; Baronchelli, Linda; Gehrels, Neil; Stern, Daniel; Mushotzky, Richard; Veilleux, Sylvain; Ueda, Yoshihiro; Crenshaw, D. Michael; Harrison, Fiona; Fischer, Travis C.; Treister, Ezequiel; BASS Team; Swift BAT Team

    2017-01-01

    We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve dierent telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics. Additionally, we discuss follow-on efforts to study the variation of [OIII] to Xray measurements, a new method to measure accretion rates from using line ratios, a sample of 100 AGN observed with NIR spectroscopy, and an effort to measure the accretion rates and obscuration with merger stage in a subsample of mergers.

  13. The Evolution of Obscuration in AGN

    NASA Astrophysics Data System (ADS)

    Treister, Ezequiel; Urry, M.; Virani, S.

    2006-09-01

    One fundamental ingredient in our understanding of the AGN population is the ratio of obscured to unobscured AGN and whether this ratio depends on other parameters like intrinsic luminosity or redshift. Observationally, deep X-ray surveys found that the obscured AGN fraction depends on luminosity. However, the dependence on redshift is less clear. In this work, we constructed the largest sample to date of AGN selected in hard X-rays, containing a total of 1229 sources, 631 of them obscured, with a high spectroscopic completeness in order to study the possible dependence of the fraction of obscured sources with redshift and/or luminosity. We confirm that this fraction decreases with increasing luminosity as previously reported and found that at the same time it increases with increasing redshift. This is the first time that this evolution is significantly detected using only optical spectroscopy to separate obscured and unobscured AGN. Additionally, we use the spectral shape and intensity of the X-ray background as a separate constraint on the evolution of the obscured AGN fraction finding consistent results. This result can be interpreted as an evolution in the location of the obscuration, from the central parsec-scale region (the torus) at low redshift to kiloparsec scales (the host galaxy) at high redshift, as it is known that most galaxies contained more dust in the past. Using these results, we calculate the integrated bolometric AGN emission finding it to be at most 5% of the total extragalactic light. Hence, while AGN contribute most of the light at X-ray wavelengths, they constitute only a small fraction of the integrated extragalactic light. We thank the support of the Centro de Astrof\\'{\\i}sica FONDAP and from NASA/{\\it INTEGRAL} grant NNG05GM79G.

  14. Fermentation and dry fractionation increase bioactivity of cloudberry (Rubus chamaemorus).

    PubMed

    Puupponen-Pimiä, Riitta; Nohynek, Liisa; Juvonen, Riikka; Kössö, Tuija; Truchado, Pilar; Westerlund-Wikström, Benita; Leppänen, Tiina; Moilanen, Eeva; Oksman-Caldentey, Kirsi-Marja

    2016-04-15

    Phenolic composition and bioactivity of cloudberry was modified by bioprocessing, and highly bioactive fractions were produced by dry fractionation of the press cake. During fermentation polymeric ellagitannins were partly degraded into ellagic acid derivatives. Phenolic compounds were differentially distributed in seed coarse and fine fractions after dry fractionation process. Tannins concentrated in fine fraction, and flavonol derivatives were mainly found in coarse fraction. Ellagic acid derivatives were equally distributed between the dry fractions. Fermentation and dry fractionation increased statistically significantly anti-adhesion and anti-inflammatory activity of cloudberry. The seed fine fraction showed significant inhibition of P fimbria-mediated haemagglutination assay of uropathogenic Escherichia coli. The seed coarse fraction significantly reduced NO and IL-6 production and iNOS expression in activated macrophages. Fermentation did not affect antimicrobial activity, but slight increase in activity was detected in dry fractions. The results indicate the potential of cloudberry in pharma or health food applications.

  15. Spitzer's contribution to the AGN population

    NASA Astrophysics Data System (ADS)

    Donley, Jennifer Lynn

    2009-06-01

    Using large multiwavelength datasets, we study obscured AGN in the distant universe that have been missed via traditional selection techniques (e.g. UV/ optical/X-ray). To do so, we take particular advantage of the mid-IR, which is minimally affected by obscuration. We first select as AGN candidates those objects whose radio emission is significantly brighter, relative to the mid-IR, than would be predicted by the well known radio/infrared correlation, indicating that the radio emission originates in the central engine. We find that of the 27 such sources identified in the CDF-N, 60% lack solid X-ray detections and 25% lack even 2s X-ray emission. The absorbing columns of the faint X-ray-detected objects indicate that they are obscured but unlikely to be Compton thick, whereas the radio-excess AGN which are X-ray non-detected are Compton-thick candidates. We similarly use the infrared emission to select IRAC (3.6-8.0 mm) power-law AGN. In these luminous AGN, the hot dust emission from the AGN fills in the gap in a galaxy's SED between the 1.6 mm stellar bump and the long-wavelength dust emission feature. While sources selected in this way are more luminous than the radio-excess AGN, we find a similar X-ray detection fraction. Of the 62 power- law galaxies in the CDF-N, only 55% are detected in the X-ray, and 15% lack evidence for even weak 2s X-ray emission. A study of their X-ray properties indicates that ~ 75% are obscured. Finally, we test IRAC color-color and infrared-excess selection criteria. We find that while these selection techniques identify a number of obscured AGN, they may also select a significant number of star-forming galaxies. By combining only the secure AGN candidates selected via all methods discussed above, we estimate that the addition of Spitzer-selected AGN candidates to the deepest X-ray selected AGN samples directly increases the number of known AGN by 54-77%, and implies a total increase to the number of AGN of 71-94%.

  16. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, D.; Zakamska, N.

    2016-06-01

    Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies. It operates by either heating or driving the gas that would otherwise be available for star formation out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been hard to come by. We have assembled a large sample of 133 radio-quiet type-2 and red AGN at 0.1AGN-ionized gas, the stellar masses of the host galaxies and their star formation rates. We then investigate the relationships between AGN luminosities, specific star formation rates (sSFR) and outflow strengths W_{90} - the 90% velocity width of the [OIII]λ5007Å line power and a proxy for the AGN-driven outflow speed. Outflow strength W_{90} is independent of sSFR for AGN selected based on their mid-IR luminosity. This is in agreement with previous work that demonstrates that star formation is not sufficient to produce the observed ionized gas outflows which have to be powered by AGN activity. More importantly, we find a negative correlation between W_{90} and sSFR in the AGN hosts with the highest star formation rates, i.e., with the highest gas content. This relationship implies that AGN with strong outflow signatures are hosted in galaxies that are more `quenched' considering their stellar mass than galaxies with weaker outflow signatures. This correlation is only seen in AGN host galaxies with SFR >100 M_{⊙} yr^{-1} where presumably the coupling of the AGN-driven wind to the gas is strongest. This observation is consistent with the AGN having a net suppression, or `negative' impact, through feedback on the galaxies' star formation history.

  17. Spectral decomposition of broad-line agns and host galaxies

    SciTech Connect

    Vanden Berk, Daniel E.; Shen, Jiajian; Yip, Ching-Wa; Schneider, Donald P.; Connolly, Andrew J.; Burton, Ross E.; Jester, Sebastian; Hall, Patrick B.; Szalay, Alex S.; Brinkmann, John; /Apache Point Observ.

    2005-09-01

    Using an eigenspectrum decomposition technique, we separate the host galaxy from the broad line active galactic nucleus (AGN) in a set of 4666 spectra from the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75. The decomposition technique uses separate sets of galaxy and quasar eigenspectra to efficiently and reliably separate the AGN and host spectroscopic components. The technique accurately reproduces the host galaxy spectrum, its contributing fraction, and its classification. We show how the accuracy of the decomposition depends upon S/N, host galaxy fraction, and the galaxy class. Based on the eigencoefficients, the sample of SDSS broad-line AGN host galaxies spans a wide range of spectral types, but the distribution differs significantly from inactive galaxies. In particular, post-starburst activity appears to be much more common among AGN host galaxies. The luminosities of the hosts are much higher than expected for normal early-type galaxies, and their colors become increasingly bluer than early-type galaxies with increasing host luminosity. Most of the AGNs with detected hosts are emitting at between 1% and 10% of their estimated Eddington luminosities, but the sensitivity of the technique usually does not extend to the Eddington limit. There are mild correlations among the AGN and host galaxy eigencoefficients, possibly indicating a link between recent star formation and the onset of AGN activity. The catalog of spectral reconstruction parameters is available as an electronic table.

  18. The Prevalence of Gas Outflows in Type 2 AGNs

    NASA Astrophysics Data System (ADS)

    Woo, Jong-Hak; Bae, Hyun-Jin; Son, Donghoon; Karouzos, Marios

    2016-02-01

    To constrain the nature and fraction of the ionized gas outflows in active galactic nuclei (AGNs), we perform a detailed analysis on gas kinematics as manifested by the velocity dispersion and shift of the [{{O}}\\{{III}}] λ5007 emission line, using a large sample of ˜39,000 type 2 AGNs at z < 0.3. First, we confirm a broad correlation between [{{O}} {{III}}] and stellar velocity dispersions, indicating that the bulge gravitational potential plays a main role in determining the [{{O}} {{III}}] kinematics. However, [{{O}} {{III}}] velocity dispersion is on average larger than stellar velocity dispersion by a factor of 1.3-1.4 for AGNs with double Gaussian [{{O}} {{III}}], suggesting that the non-gravitational component, i.e., outflows, is almost comparable to the gravitational component. Second, the increase of the [{{O}} {{III}}] velocity dispersion (after normalized by stellar velocity dispersion) with both AGN luminosity and Eddington ratio suggests that non-gravitational kinematics are clearly linked to AGN accretion. The distribution in the [{{O}} {{III}}] velocity-velocity dispersion diagram dramatically expands toward large values with increasing AGN luminosity, implying that the launching velocity of gas outflows increases with AGN luminosity. Third, the majority of luminous AGNs present the non-gravitational kinematics in the [{{O}} {{III}}] profile. These results suggest that ionized gas outflows are prevalent among type 2 AGNs. On the other hand, we find no strong trend of the [{{O}} {{III}}] kinematics with radio luminosity, once we remove the effect of the bulge gravitational potential, indicating that ionized gas outflows are not directly related to radio activity for the majority of type 2 AGNs.

  19. PRIMUS: INFRARED AND X-RAY AGN SELECTION TECHNIQUES AT 0.2 < z < 1.2

    SciTech Connect

    Mendez, Alexander J.; Coil, Alison L.; Aird, James; Diamond-Stanic, Aleksandar M.; Moustakas, John; Blanton, Michael R.; Cool, Richard J.; Eisenstein, Daniel J.; Wong, Kenneth C.; Zhu Guangtun

    2013-06-10

    We present a study of Spitzer/IRAC and X-ray active galactic nucleus (AGN) selection techniques in order to quantify the overlap, uniqueness, contamination, and completeness of each. We investigate how the overlap and possible contamination of the samples depend on the depth of both the IR and X-ray data. We use Spitzer/IRAC imaging, Chandra and XMM-Newton X-ray imaging, and spectroscopic redshifts from the PRism MUlti-object Survey to construct galaxy and AGN samples at 0.2 < z < 1.2 over 8 deg{sup 2}. We construct samples over a wide range of IRAC flux limits (SWIRE to GOODS depth) and X-ray flux limits (10 ks to 2 Ms). We compare IR-AGN samples defined using both the IRAC color selection of Stern et al. and Donley et al. with X-ray-detected AGN samples. For roughly similar depth IR and X-ray surveys, we find that {approx}75% of IR-selected AGNs are also identified as X-ray AGNs. This fraction increases to {approx}90% when comparing against the deepest X-ray data, indicating that at most {approx}10% of IR-selected AGNs may be heavily obscured. The IR-AGN selection proposed by Stern et al. suffers from contamination by star-forming galaxies at various redshifts when using deeper IR data, though the selection technique works well for shallow IR data. While similar overall, the IR-AGN samples preferentially contain more luminous AGNs, while the X-ray AGN samples identify a wider range of AGN accretion rates including low specific accretion rate AGNs, where the host galaxy light dominates at IR wavelengths. The host galaxy populations of the IR and X-ray AGN samples have similar rest-frame colors and stellar masses; both selections identify AGNs in blue, star-forming and red, quiescent galaxies.

  20. The Two Faces of Fractionated Photodynamic Therapy: Increasing Efficacy With Light Fractionation or Adjuvant Use of Fractional Laser Technology.

    PubMed

    Juhasz, Margit L W; Levin, Melissa K; Marmur, Ellen S

    2016-11-01

    "Fractionated photodynamic therapy (PDT)" is a new term being used by dermatologists to describe advances in PDT technology including fractionated light or the adjuvant use of fractional lasers. Although dermatologists have used PDT since the early 1990s for the treatment of photodamage and precancerous lesions, newer developments in technology have allowed for the treatment of non-melanoma skin cancers (NMSCs), in ammatory disorders, and even uses in the eld of anti-aging. Recent developments in fractionated light therapy have allowed for PDT with dark intervals and two-fold illumination schemes to increase cellular damage and apoptosis. Combining PDT with fractional laser technology has allowed for enhanced dermal penetration of topical photosensitizers including 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL), as well as increased ef cacy of treatment. These advances in PDT technology will allow for increased convenience, decreased treatment time, only one application of topical photosensitizer, and decreased cost to the patient and dermatologist. J Drugs Dermatol. 2016;15(11):1324-1328..

  1. Optically-selected AGN

    NASA Astrophysics Data System (ADS)

    Richard, Gordon

    2016-08-01

    will discuss the selection and properties of optically-selected AGN as contrasted with other multi-wavelength investigations. While optical surveys are able to identify *more* AGNs than other wavelengths, this size comes with a bias towards brighter, unobscured sources. Although optical surveys are not ideal for probing obscured AGNs, I will discuss how they can guide our search for them. The bias towards unobscured sources in the optical is partially mitigated, however, by an increase in information content for the sources that *are* identified---in the form of physics probed by the combination of optical continuum, absorption, and emission. An example is the ability to estimate the mass of AGNs based on the optical/UV emission lines. I will discuss the range of mass (and accretion rate) probed by the optical in addition to serious biases in the black hole mass scaling relations that corrupt these estimates at high redshift.

  2. Host galaxies of luminous z ∼ 0.6 quasars: major mergers are not prevalent at the highest AGN luminosities

    NASA Astrophysics Data System (ADS)

    Villforth, C.; Hamilton, T.; Pawlik, M. M.; Hewlett, T.; Rowlands, K.; Herbst, H.; Shankar, F.; Fontana, A.; Hamann, F.; Koekemoer, A.; Pforr, J.; Trump, J.; Wuyts, S.

    2017-04-01

    Galaxy interactions are thought to be one of the main triggers of active galactic nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime is substantial. Evidence for a connection between mergers and AGN, however, remains mixed. Possible triggering mechanisms remain particularly poorly understood for luminous AGN, which are thought to require triggering by major mergers, rather than secular processes. We analyse the host galaxies of a sample of 20 optically and X-ray selected luminous AGN (log(Lbol [erg s-1]) > 45) at z ∼ 0.6 using Hubble Space Telescope Wide Field Camera 3 data in the F160W/H band. 15/20 sources have resolved host galaxies. We create a control sample of mock AGN by matching the AGN host galaxies to a control sample of non-AGN galaxies. Visual signs of disturbances are found in about 25 per cent of sources in both the AGN hosts and control galaxies. Using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. We find no signs that major mergers play a dominant role in triggering AGN at high luminosities, suggesting that minor mergers and secular processes dominate AGN triggering up to the highest AGN luminosities. The upper limit on the enhanced fraction of major mergers is ≤20 per cent. While major mergers might increase the incidence of luminous AGN, they are not the prevalent triggering mechanism in the population of unobscured AGN.

  3. Constraining the properties of AGN host galaxies with spectral energy distribution modelling

    NASA Astrophysics Data System (ADS)

    Ciesla, L.; Charmandaris, V.; Georgakakis, A.; Bernhard, E.; Mitchell, P. D.; Buat, V.; Elbaz, D.; LeFloc'h, E.; Lacey, C. G.; Magdis, G. E.; Xilouris, M.

    2015-04-01

    Detailed studies of the spectral energy distribution (SED) of normal galaxies have increasingly been used to understand the physical mechanism dominating their integrated emission, mainly owing to the availability of high quality multi-wavelength data from the UV to the far-infrared (FIR). However, systems hosting dust-enshrouded nuclear starbursts and/or an accreting supermassive black hole (an active galactic nucleus or AGN) are especially challenging to study. This is due to the complex interplay between the heating by massive stars and the AGN, the absorption and emission of radiation from dust, as well as the presence of the underlying old stellar population. We used the latest release of CIGALE, a fast state-of-the-art galaxy SED-fitting model relying on energy balance, to study the influence of an AGN in a self consistent manner in estimating both the star formation rate (SFR) and stellar mass in galaxies, as well as to calculate the contribution of the AGN to the power output of the host. Using the semi-analytical galaxy formation model galform, we created a suite of mock galaxy SEDs using realistic star formation histories (SFH). We also added an AGN of Type-1, Type-2, or intermediate-type whose contribution to the bolometric luminosity can be variable. We performed an SED-fitting of these catalogues with CIGALE, assuming three different SFHs: a single-exponentially-decreasing (1τ-dec), a double-exponentially-decreasing (2τ-dec), and a delayed SFH. Constraining the overall contribution of an AGN to the total infrared luminosity (fracAGN) is very challenging for fracAGN< 20%, with uncertainties of ~5-30% for higher fractions depending on the AGN type, while FIR and sub-mm are essential. The AGN power has an impact on the estimation of M∗ in Type-1 and intermediate-type AGNs but has no effect on galaxies hosting Type-2 AGNs. We find that in the absence of AGN emission, the best estimates of M∗ are obtained using the 2τ-dec model but at the expense of

  4. VizieR Online Data Catalog: Catalog of Type-1 AGNs from SDSS-DR7 (Oh+, 2015)

    NASA Astrophysics Data System (ADS)

    Oh, K.; Yi, S. K.; Schawinski, K.; Koss, M.; Trakhtenbrot, B.; Soto, K.

    2015-08-01

    We have recently identified a substantial number of type 1 active galactic nuclei (AGNs) featuring weak broad-line regions (BLRs) at z<0.2 from detailed analysis of galaxy spectra in the Sloan Digital Sky Survey Data Release 7. These objects predominantly show a stellar continuum but also a broad Hα emission line, indicating the presence of a low-luminosity AGN oriented so that we are viewing the central engine directly without significant obscuration. These accreting black holes have previously eluded detection due to their weak nature. The newly discovered BLR AGNs have increased the number of known type 1 AGNs by 49%. Some of these new BLR AGNs were detected with the Chandra X-ray Observatory, and their X-ray properties confirm that they are indeed type 1 AGNs. Based on our new and more complete catalog of type 1 AGNs, we derived the type 1 fraction of AGNs as a function of [OIII]λ5007 emission luminosity and explored the possible dilution effect on obscured AGNs due to star formation. The new type 1 AGN fraction shows much more complex behavior with respect to black hole mass and bolometric luminosity than has been suggested previously by the existing receding torus model. The type 1 AGN fraction is sensitive to both of these factors, and there seems to be a sweet spot (ridge) in the diagram of black hole mass and bolometric luminosity. Furthermore, we present the possibility that the Eddington ratio plays a role in determining opening angles. (2 data files).

  5. Radio-AGN feedback: when the little ones were monsters

    NASA Astrophysics Data System (ADS)

    Williams, W. L.; Röttgering, H. J. A.

    2015-06-01

    We present a study of the evolution of the fraction of radio-loud active galactic nuclei (AGN) as a function of their host stellar mass. We make use of two samples of radio galaxies: one in the local Universe, 0.01 < z ≤ 0.3, using a combined SDSS-NVSS (Sloan Digital Sky Survey NRAO Very Large Array Sky Survey) sample and the other at higher redshifts, 0.5 < z ≤ 2, constructed from the VLA-COSMOS_DEEP Radio Survey at 1.4 GHz and a Ks-selected catalogue of the COSMOS/UltraVISTA field. We observe an increase of more than an order of magnitude in the fraction of lower mass galaxies (M* < 1010.75 M⊙) which host radio-loud AGN with radio powers P1.4 GHz > 1024 W Hz-1 at z ˜ 1-2 while the radio-loud fraction for higher mass galaxies (M* > 1011.25 M⊙) remains the same. We argue that this increase is driven largely by the increase in cold or radiative mode accretion with increasing cold gas supply at earlier epochs. The increasing population of low-mass radio-loud AGN can thus explain the upturn in the radio luminosity function at high redshift which is important for understanding the impact of AGN feedback in galaxy evolution.

  6. Increased diffuse radiation fraction does not significantly accelerate plant growth

    NASA Astrophysics Data System (ADS)

    Angert, Alon; Krakauer, Nir

    2010-05-01

    A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse light and NPP is actually quite weak on annual timescales. The inconsistency of these data with the modelling results may arise because the relationships used to quantify the enhancement of NPP were calibrated with eddy covariance measurements of hourly carbon uptake. The effect of diffuse-light fraction on carbon uptake could depend on timescale, since this effect varies rapidly as sun angle and cloudiness change, and since plants can respond dynamically over various timescales to change in incoming radiation. Volcanic eruptions, such as the eruption of Mount Pinatubo in 1991, provide the best available tests for the effect of an annual-scale increase in the diffuse light fraction. Following the Pinatubo Eruption, in 1992 and 1993, a sharp decrease in the atmospheric CO2 growth rate was observed. This could have resulted from enhanced plant carbon uptake. Mercado et al. (2009) argue that largely as a result of the (volcanic aerosol driven) increase in diffuse light fraction, NPP was elevated in 1992, particularly between 25° N-45° N where annual NPP was modelled to be ~0.8 PgC (~10%) above average. In a previous study (Angert et al., 2004) a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH), was used to show that a diffuse-radiation driven increase in NPP in the extratropics will enhance carbon uptake mostly in summer, leading to a lower CO2 seasonal minimum. Here we use a 'toy model' to show that this conclusion is general and model-independent. The model shows that an enhanced sink of 0.8 PgC, similar to that modelled by Mercado et al. (2009

  7. The cosmic evolution of massive black holes in the Horizon-AGN simulation

    NASA Astrophysics Data System (ADS)

    Volonteri, M.; Dubois, Y.; Pichon, C.; Devriendt, J.

    2016-08-01

    We analyse the demographics of black holes (BHs) in the large-volume cosmological hydrodynamical simulation Horizon-AGN. This simulation statistically models how much gas is accreted on to BHs, traces the energy deposited into their environment and, consequently, the back-reaction of the ambient medium on BH growth. The synthetic BHs reproduce a variety of observational constraints such as the redshift evolution of the BH mass density and the mass function. Strong self-regulation via AGN feedback, weak supernova feedback, and unresolved internal processes result in a tight BH-galaxy mass correlation. Starting at z ˜ 2, tidal stripping creates a small population of BHs over-massive with respect to the halo. The fraction of galaxies hosting a central BH or an AGN increases with stellar mass. The AGN fraction agrees better with multi-wavelength studies, than single-wavelength ones, unless obscuration is taken into account. The most massive haloes present BH multiplicity, with additional BHs gained by ongoing or past mergers. In some cases, both a central and an off-centre AGN shine concurrently, producing a dual AGN. This dual AGN population dwindles with decreasing redshift, as found in observations. Specific accretion rate and Eddington ratio distributions are in good agreement with observational estimates. The BH population is dominated in turn by fast, slow, and very slow accretors, with transitions occurring at z = 3 and z = 2, respectively.

  8. The Changing Looks of AGN

    NASA Astrophysics Data System (ADS)

    LaMassa, S.

    2015-09-01

    According to the AGN unification model, the difference between Type 1 and Type 2 AGN is explained by the orientation of a circumnuclear obscuring torus to the observer's line of sight. Observations of seemingly anomalous sources challenge this theory. A handful of AGN have been discovered which have transitioned from Type 1, with strong, prominent broad-emission lines, to Type 1.8 or 1.9, with weak broad components to only H-alpha and/or H-beta, or vice versa. The rate of discovery of these objects has increased this past year thanks to the Sloan Digital Sky Survey BOSS and TDSS surveys which have repeated spectroscopic observations of AGN. While in some cases this transition can be explained by circumnuclear clouds eclipsing the broad line region, it seems clear that stochastic accretion is responsible for other changing-look AGN. In this talk, I will discuss the changing-look AGN discovered thus far and the implications these objects have for AGN unification and the intermittency of AGN activity.

  9. The 60-month all-sky BAT Survey of AGN and the Anisotropy of Nearby AGN

    SciTech Connect

    Ajello, M.; Alexander, D.M.; Greiner, J.; Madejski, G.M.; Gehrels, N.; Burlon, D.; /Garching, Max Planck Inst., MPE

    2012-04-02

    Surveys above 10 keV represent one of the the best resources to provide an unbiased census of the population of Active Galactic Nuclei (AGN). We present the results of 60 months of observation of the hard X-ray sky with Swift/BAT. In this timeframe, BAT detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGN, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of {approx}2 larger over similarly complete sets of AGN. Our sample contains (at least) 15 bona-fide Compton-thick AGN and 3 likely candidates. Compton-thick AGN represent a {approx}5% of AGN samples detected above 15 keV. We use the BAT dataset to refine the determination of the LogN-LogS of AGN which is extremely important, now that NuSTAR prepares for launch, towards assessing the AGN contribution to the cosmic X-ray background. We show that the LogN-LogS of AGN selected above 10 keV is now established to a {approx}10% precision. We derive the luminosity function of Compton-thick AGN and measure a space density of 7.9{sub -2.9}{sup +4.1} x 10{sup -5} Mpc{sup -3} for objects with a de-absorbed luminosity larger than 2 x 10{sup 42} erg s{sup -1}. As the BAT AGN are all mostly local, they allow us to investigate the spatial distribution of AGN in the nearby Universe regardless of absorption. We find concentrations of AGN that coincide spatially with the largest congregations of matter in the local ({le} 85 Mpc) Universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions.

  10. Active galactic nuclei from He II: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Bär, Rudolf E.; Weigel, Anna K.; Sartori, Lia F.; Oh, Kyuseok; Koss, Michael; Schawinski, Kevin

    2017-04-01

    In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the He II λ4685 emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II-based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63 915 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02 < z < 0.05 and use both the conventional BPT emission line diagnostic diagrams, as well as the He II diagram to identify AGN. In this sample, 1075 galaxies are selected as AGN using the BPT diagram, while additional 234 galaxies are identified as AGN using the He II diagnostic diagram, representing a 22 per cent increase of AGN in the parent galaxy sample. We explore the host galaxy properties of these new He II-selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from star formation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II-based diagnostic. Finally, we discuss how this technique can help inform galaxy/black hole coevolution scenarios.

  11. Active Galactic Nuclei from He II: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Baer, Rudolf E.; Weigel, Anna; Sartori, Lia F.; Oh, Kyuseok; Koss, Michael; Schawinski, Kevin

    2017-01-01

    In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the He II emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 81,192 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02 < z < 0.05 and apply both the conventional BPT emission line diagnostic diagrams, as well as the He II diagram to identify AGN. In this sample, 1,075 galaxies are selected as AGN using the BPT diagram, while an additional 234 galaxies are identified as AGN using the He II diagnostic, representing a 22% increase of AGN in the parent galaxy sample. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II based diagnostic. Finally, we explore the host galaxy properties of these new He II selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from star-formation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We discuss how this technique can help inform galaxy/black hole co-evolution scenarios.

  12. AGN multi-wavelength identification and host galaxy properties

    NASA Astrophysics Data System (ADS)

    Azadi, Mojegan; Coil, Alison L.; MOSDEF Team; PRIMUS Team

    2017-01-01

    I present results on AGN identification, selection biases, and host galaxy properties at z~2.3 and results on the relation between AGN accretion and star formation activity at z~0.8. In the MOSDEF survey, with a sample of X-ray, IR, and optically selected AGN at z~2.3, using rest-frame optical spectra obtained with the Keck/MOSFIRE instrument, I find clear selection biases in identifying AGN at these wavelengths. There is a strong bias against identifying AGN at any wavelength in low mass galaxies, and an additional bias against identifying IR AGN in the most massive galaxies. While AGN hosts span a wide range of SFR, IR AGN are mainly in less dusty galaxies with relatively higher SFR and optical AGN are in dusty galaxies with relatively lower SFR in our sample. X-ray AGN selection does not display a bias with host SFR. I also consider the relation between the growth of galaxies and their SMBHs using a large sample of X-ray AGN in the PRIMUS survey. I do not find a significant correlation between SFR and AGN instantaneous luminosity. However, I find a weak but significant correlation between the average luminosity of AGN and SFR, which likely reflects that AGN luminosities vary on shorter timescales than host galaxies SFR. My results indicate that AGN are also often hosted by quiescent galaxies, and within both the star-forming and quiescent galaxy populations the probability of hosting an AGN is a power-law distribution as a function of specific accretion rate. However, at a given stellar mass, I find that a star-forming galaxy is ~2-3 times more likely than a quiescent galaxy to host an AGN of a given specific accretion rate. The probability of a galaxy hosting an AGN is constant across the main sequence of star formation, while in quiescent galaxies increases with SFR.

  13. Higher prevalence of X-ray selected AGN in intermediate-age galaxies up to z ˜ 1

    NASA Astrophysics Data System (ADS)

    Hernán-Caballero, Antonio; Alonso-Herrero, Almudena; Pérez-González, Pablo G.; Barro, Guillermo; Aird, James; Ferreras, Ignacio; Cava, Antonio; Cardiel, Nicolás; Esquej, Pilar; Gallego, Jesús; Nandra, Kirpal; Rodríguez-Zaurín, Javier

    2014-10-01

    We analyse the stellar populations in the host galaxies of 53 X-ray selected optically dull active galactic nuclei (AGN) at 0.34 < z < 1.07 with ultradeep (mAB = 26.5, 3σ) optical medium-band (R ˜ 50) photometry from the Survey for High-z Absorption Red and Dead Sources (SHARDS). The spectral resolution of SHARDS allows us to consistently measure the strength of the 4000 Å break, Dn(4000), a reliable age indicator for stellar populations. We confirm that most X-ray selected moderate-luminosity AGN (LX < 1044 erg s-1) are hosted by massive galaxies (typically M* >1010.5 M⊙) and that the observed fraction of galaxies hosting an AGN increases with the stellar mass. A careful selection of random control samples of inactive galaxies allows us to remove the stellar mass and redshift dependences of the AGN fraction to explore trends with several stellar age indicators. We find no significant differences in the distribution of the rest-frame U - V colour for AGN hosts and inactive galaxies, in agreement with previous results. However, we find significantly shallower 4000 Å breaks in AGN hosts, indicative of younger stellar populations. With the help of a model-independent determination of the extinction, we obtain extinction-corrected U - V colours and light-weighted average stellar ages. We find that AGN hosts have younger stellar populations and higher extinction compared to inactive galaxies with the same stellar mass and at the same redshift. We find a highly significant excess of AGN hosts with Dn(4000) ˜ 1.4 and light-weighted average stellar ages of 300-500 Myr, as well as a deficit of AGN in intrinsic red galaxies. We interpret failure in recognizing these trends in previous studies as a consequence of the balancing effect in observed colours of the age-extinction degeneracy.

  14. Detecting Dual AGN at High Redshift

    NASA Astrophysics Data System (ADS)

    Barrows, Robert S.

    2012-01-01

    The existence of supermassive black holes (SMBHs) in most, if not all, galaxies, along with observations of galaxy mergers, suggests that pairs of SMBHs should exist for some time in the merger remnant. Observational evidence for these systems at kpc-scale separations (i.e. dual AGN) has dramatically increased recently through a combination of spectral and morphological selections. I discuss observations of CXOXBJ142607.6+353351 (CXOJ1426+35), a candidate dual AGN at z=1.175, and put its properties, including significant obscuration, within the context of other candidate/confirmed dual AGN at lower redshifts. Though dual AGN are expected to be more common at higher redshifts, they are more difficult to detect. Furthermore, adding to the difficulties of detection are a number of other physical mechanisms which can mimic the spectroscopic signature of two Type 2 AGN. In particular, I will discuss the possibility of strong outflows from an AGN. These outflow phenomena can be an important feedback mechanism in galaxies and are apparently common in AGN, making them a viable alternative to the dual AGN scenario. Based on our candidate's luminosity and emission line intensities, we find that an outflow is a possibility. If this is the case, such an outflow would be especially strong and has implications for AGN feedback in galaxies. However, the dual AGN scenario cannot be ruled out, and at z=1.175, the two putative AGN could potentially be resolved with Chandra. Other candidate dual AGN at similar redshifts and with significant obscuration could also be confirmed this way. This research was sponsored by the Strategic University Research Partnership Program, the National Aeronautics and Space Administration and the Arkansas NASA EPSCoR program.

  15. AGN Absorption Linked to Host Galaxies

    NASA Astrophysics Data System (ADS)

    Juneau, Stéphanie

    2014-07-01

    Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3AGN tracers in the X-ray, optical spectra, mid-infrared, and radio regimes, we found a twice higher AGN fraction than previous studies, thanks to the combined AGN identification methods and in particular the recent Mass-Excitation (MEx) diagnostic diagram. We furthermore find an intriguing relation between AGN X-ray absorption and the specific star formation rate (sSFR) of the host galaxies, indicating a physical link between X-ray absorption and either the gas fraction or the gas geometry in the hosts. These findings have implications for our current understanding of both the AGN unification model and the nature of the black hole-galaxy connection.

  16. Multi-faceted AGN

    NASA Astrophysics Data System (ADS)

    Farrar, Glennys R.; Chen, Yanping; Dai, Yuxiao; Zaw, Ingyin

    2016-08-01

    An interesting question is how frequently an object is an AGN by multiple different criteria — e.g., is simultaneously a narrow-line optical AGN and an X-ray or radio AGN, possibly as a function of luminosities in the various wavebands and perhaps host galaxy type. Answering such questions quantitatively has been difficult up to now because of the lack of a complete, uniformly selected optical AGN catalog. Here we report first results of such an analysis, using the new, all-sky catalog of uniformly selected optical AGNs from Zaw, Chen and Farrar (2016), the Swift-BAT 70-month catalog of X-ray AGN (Baumgartner et al., 2013), and the van Velzen et al. (2012) catalog of radio AGN.

  17. AGN-starburst evolutionary connection: a physical interpretation based on radiative feedback

    NASA Astrophysics Data System (ADS)

    Ishibashi, W.; Fabian, A. C.

    2016-12-01

    Observations point towards a close connection between nuclear starbursts, active galactic nuclei (AGN), and outflow phenomena. An evolutionary sequence, starting from a dust-obscured ultra-luminous infrared galaxy and eventually leading to an unobscured optical quasar, has been proposed and discussed in the literature. AGN feedback is usually invoked to expel the obscuring gas and dust in a blow-out event, but the underlying physical mechanism remains unclear. We consider AGN feedback driven by radiation pressure on dust, which directly acts on the obscuring dusty gas. We obtain that radiative feedback can potentially disrupt dense gas in the infrared-optically thick regime, and that an increase in the dust-to-gas fraction leads to an increase in the effective Eddington ratio. Thus, the more dusty gas is preferentially expelled by radiative feedback, and the central AGN is prone to efficiently remove its own obscuring dust cocoon. Large amounts of dust imply heavy obscuration but also powerful feedback, suggesting a causal link between dust obscuration and blow-out. In this picture, AGN feedback and starburst phenomena are intrinsically coupled through the production of dust in supernova explosions, leading to a natural interpretation of the observed evolutionary path.

  18. Combining Chandra Observations and Near-Infrared Imaging to Search for Dual AGNs Among Double-Peaked [O III] SDSS AGN

    NASA Astrophysics Data System (ADS)

    McGurk, Rosalie C.; Max, Claire E.; Holden, Bradford; Shields, Gregory A.; Medling, Anne

    2016-01-01

    When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see close pairs of active galactic nuclei (AGNs), or dual AGNs, in a fraction of galaxy mergers. However, finding them remains a challenge. We studied a sample of double-peaked SDSS [O III] AGNs using Keck 2 Laser Guide Star Adaptive Optics assisted imaging to find that 30% of double-peaked SDSS AGNs have two spatial components within a 3" radius. However, the identity of the companion object is not revealed with imaging; X-ray observations can confirm these galaxy pairs as systems containing two AGNs. We performed Chandra X-ray ACIS-S observations on 12 double-peaked candidate dual AGNs with a possible near-infrared companion 1-3" away. Using our observations and 8 archival observations of additional candidate dual AGNs, we compare the distribution of X-ray photons to our spatially double near-IR images, measure X-ray luminosities and hardness ratios, and estimate column densities. Additionally, we can compare our near-IR spatially double candidates with 7 double-peaked [O III] SDSS AGNs that are spatially single in our near-IR imaging and have archival Chandra ACIS-S observations. By assessing what fraction of double- peaked emission line SDSS AGNs are true dual AGNs, we can better determine whether double-peaked [O III] is an efficient dual AGN indicator and constrain the statistics of dual AGNs

  19. Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission

    NASA Astrophysics Data System (ADS)

    Lyu, Jianwei; Rieke, G. H.; Shi, Yong

    2017-02-01

    To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z ≲ 0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ∼60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3–500 μm SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.

  20. THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

    SciTech Connect

    Lusso, E.; Hennawi, J. F.; Richards, G. T.; Comastri, A.; Zamorani, G.; Vignali, C.; Gilli, R.; Treister, E.; Schawinski, K.; Salvato, M.

    2013-11-10

    The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 band COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.

  1. Obscured AGN Accretion Across Cosmic Time

    NASA Astrophysics Data System (ADS)

    Coil, Alison

    We propose to combine data from XMM-Newton, the Chandra X-ray Observatory, and the Spitzer Space Telescope with ground-based optical spectroscopy from Keck and Magellan to measure the relationship between AGN obscuration and accretion activity over the bulk of cosmic history. This work will establish the prominence of both obscured and unobscured growth phases of black holes and shed light on the processes that trigger and fuel AGN as a function of time. We will complete three complementary projects that focus on a) understanding the completeness and biases of AGN selection at mid-IR versus X-ray wavelengths, b) tracing optical obscuration as a function of luminosity and redshift, and c) measuring the distribution and evolution of X-ray absorption of AGN. We will undertake a study of AGN demographics comparing selection techniques at three different wavelengths: mid-IR selection using data from the Spitzer Space Telescope, X- ray selection using data from the XMM-Newton and Chandra satellites, and broad-line optical selection using PRIMUS spectroscopy. We will determine the overlap and uniqueness of samples created using each method, to quantify the completeness and biases inherent in AGN selection at each wavelength. This will lead to a constraint on the fraction of heavily obscured, Compton-thick AGN to z~1. To study the optical obscuration of AGN, we will use three recently-completed spectroscopic surveys -- PRIMUS, DEEP2, and our own Keck program -- to robustly determine the ratio of unobscured (broad-line) to obscured (non--broad-line) X-ray selected AGN as a function of luminosity from z~0.2 to z~3. We will utilize the well- understood selection functions and characterize the AGN completeness of each survey as a function of redshift, magnitude, and obscuration properties. This will allow us to correct for a variety of observational effects to measure the underlying joint redshift- and luminosity-dependence of optical obscuration, which has direct implications

  2. The Angular Clustering of WISE-Selected AGN: Different Haloes for Obscured and Unobscured AGN

    NASA Astrophysics Data System (ADS)

    Yan, Lin

    2015-08-01

    We calculate the angular correlation function for a sample of 170,000 AGN extracted from the Wide-field Infrared Survey Explorer (WISE) catalog, selected to have red mid-IR colors (W1 - W2 > 0.8) and 4.6 micron flux densities brighter than 0.14 mJy). The sample is expected to be >90% reliable at identifying AGN, and to have a mean redshift of z=1.1. In total, the angular clustering of WISE-AGN is roughly similar to that of optical AGN. We cross-match these objects with the photometric SDSS catalog and distinguish obscured sources with (r - W2) > 6 from bluer, unobscured AGN. Obscured sources present a higher clustering signal than unobscured sources. Since the host galaxy morphologies of obscured AGN are not typical red sequence elliptical galaxies and show disks in many cases, it is unlikely that the increased clustering strength of the obscured population is driven by a host galaxy segregation bias. By using relatively complete redshift distributions from the COSMOS survey, we find obscured sources at mean redshift z=0.9 have a bias of b = 2.9 \\pm 0.6 and are hosted in dark matter halos with a typical mass of log(M/M_odot)~13.5. In contrast, unobscured AGN at z~1.1 have a bias of b = 1.6 \\pm 0.6 and inhabit halos of log(M/M_odot)~12.4. These findings suggest that obscured AGN inhabit denser environments than unobscured AGN, and are difficult to reconcile with the simplest AGN unification models, where obscuration is driven solely by orientation.

  3. Identifying Distant AGNs

    NASA Astrophysics Data System (ADS)

    Trouille, Laura; Barger, Amy; Tremonti, Christy

    2014-07-01

    The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/Hβ versus [NII]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by AGN activity (BPT-AGN). Yet the BPT diagram is limited to z<0.5, the redshift at which [NII]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g-z color, [NeIII]λ3869, and [OII]λλ3726+3729 and can be used for galaxies out to z<1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray selected AGNs as BPT-SF.

  4. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, Dominika; Zakamska, Nadia L.; MaNGA-GMOS Team

    2017-01-01

    Feedback from actively accreting SMBHs (Active Galactic Nuclei, AGN) is now widely considered to be the main driver in regulating the growth of massive galaxies. Observational proof for this scenario has, however, been hard to come by. Many attempts at finding a conclusive observational proof that AGN may be able to quench star formation and regulate the host galaxies' growth have shown that this problem is highly complex.I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN. I will describe recent efforts in our group of relating feedback signatures to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history (Wylezalek+2016a,b). Furthermore, I will show that powerful AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of the galaxy. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and outflows that are potentially very relevant for understanding the role of AGN in galaxy evolution (Wylezalek+2016c)!

  5. Method of increasing anhydrosugars, pyroligneous fractions and esterified bio-oil

    DOEpatents

    Steele, Philip H; Yu, Fei; Li, Qi; Mitchell, Brian

    2014-12-30

    The device and method are provided to increase anhydrosugars yield during pyrolysis of biomass. This increase is achieved by injection of a liquid or gas into the vapor stream of any pyrolysis reactor prior to the reactor condensers. A second feature of our technology is the utilization of sonication, microwave excitation, or shear mixing of the biomass to increase the acid catalyst rate for demineralization or removal of hemicellulose prior to pyrolysis. The increased reactivity of these treatments reduces reaction time as well as the required amount of catalyst to less than half of that otherwise required. A fractional condensation system employed by our pyrolysis reactor is another feature of our technology. This system condenses bio-oil pyrolysis vapors to various desired fractions by differential temperature manipulation of individual condensers comprising a condenser chain.

  6. Neutrinos from AGN

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes; White, Nicholas E. (Technical Monitor)

    2000-01-01

    The great penetrating power of neutrinos makes them ideal probe of astrophysical sites and conditions inaccessible to other forms of radiation. These are the centers of stars (collapsing or not) and the centers of Active Galactic Nuclei (AGN). It has been suggested that AGN presented a very promising source of high energy neutrinos, possibly detectable by underwater neutrino detectors. This paper reviews the evolution of ideas concerning the emission of neutrinos from AGN in view of the more recent developments in gamma-ray astronomy and their implications for the neutrino emission from these class of objects.

  7. The VIMOS VLT Deep Survey: the faint type-1 AGN sample

    NASA Astrophysics Data System (ADS)

    Gavignaud, I.; Bongiorno, A.; Paltani, S.; Mathez, G.; Zamorani, G.; Møller, P.; Picat, J. P.; Le Brun, V.; Marano, B.; Le Fèvre, O.; Bottini, D.; Garilli, B.; Maccagni, D.; Scaramella, R.; Scodeggio, M.; Tresse, L.; Vettolani, G.; Zanichelli, A.; Adami, C.; Arnaboldi, M.; Arnouts, S.; Bardelli, S.; Bolzonella, M.; Cappi, A.; Charlot, S.; Ciliegi, P.; Contini, T.; Foucaud, S.; Franzetti, P.; Guzzo, L.; Ilbert, O.; Iovino, A.; McCracken, H. J.; Marinoni, C.; Mazure, A.; Meneux, B.; Merighi, R.; Pellò, R.; Pollo, A.; Pozzetti, L.; Radovich, M.; Zucca, E.; Bondi, M.; Busarello, G.; Cucciati, O.; de la Torre, S.; Gregorini, L.; Lamareille, F.; Mellier, Y.; Merluzzi, P.; Ripepi, V.; Rizzo, D.; Vergani, D.

    2006-10-01

    We present the type-1 active galactic nuclei (AGN) sample extracted from the VIMOS VLT Deep Survey's first observations of 21 000 spectra in 1.75 deg^2. This sample, which is purely magnitude-limited and free of morphological or color-selection biases, contains 130 broad-line AGN (BLAGN) spectra with redshift up to 5. Our data are divided into a wide (I_AB ≤ 22.5) and a deep (I_AB ≤ 24) subsample containing 56 and 74 objects, respectively. Because of its depth and selection criteria, this sample is uniquely suited for studying the population of faint type-1 AGN. Our measured surface density (~472 ± 48 BLAGN per square degree with I_AB ≤ 24) is significantly higher than that of any other optically selected sample of BLAGN with spectroscopic confirmation. By applying a morphological and color analysis to our AGN sample, we find that (1) ~23 % of the AGN brighter than I_AB=22.5 are classified as extended, and this percentage increases to ~42% for those with z < 1.6; (2) a non-negligible fraction of our BLAGN are lying close to the color-space area occupied by stars in the u^*-g' versus g'-r' color-color diagram. This leads us to the conclusion that the classical optical-ultraviolet preselection technique, if employed at such deep magnitudes (I_AB=22.5) in conjuction with a preselection of point-like sources, can miss up to ~35% of the AGN population. Finally, we present a composite spectrum of our sample of objects. While the continuum shape is very similar to that of the SDSS composite at short wavelengths, it is much redder than that of the SDSS composite at λ ≥ 3000 Å. We interpret this as due to significant contamination from emission of the host galaxies, as expected from the faint absolute magnitudes sampled by our survey.

  8. Targeting Enox1 in tumor stroma increases the efficacy of fractionated radiotherapy

    PubMed Central

    Smith, Clayton A.; Mont, Stacey; Traver, Geri; Sekhar, Konjeti R.; Crooks, Peter A.; Freeman, Michael L.

    2016-01-01

    The goal of this investigation was to clarify the question of whether targeting Enox1 in tumor stroma would synergistically enhance the survival of tumor-bearing mice treated with fractionated radiotherapy. Enox1, a NADH oxidase, is expressed in tumor vasculature and stroma. However, it is not expressed in many tumor types, including HT-29 colorectal carcinoma cells. Pharmacological inhibition of Enox1 in endothelial cells inhibited repair of DNA double strand breaks, as measured by γH2AX and 53BP1 foci formation, as well as neutral comet assays. For 4 consecutive days athymic mice bearing HT-29 hindlimb xenografts were injected with a small molecule inhibitor of Enox1 or solvent control. Tumors were then administered 2 Gy of x-rays. On day 5 tumors were administered a single ‘top-up’ fraction of 30 Gy, the purpose of which was to amplify intrinsic differences in the radiation fractionation regimen produced by Enox1 targeting. Pharmacological targeting of Enox1 resulted in 80% of the tumor-bearing mice surviving at 90 days compared to only 40% of tumor-bearing mice treated with solvent control. The increase in survival was not a consequence of reoxygenation, as measured by pimonidazole immunostaining. These results are interpreted to indicate that targeting of Enox1 in tumor stroma significantly enhances the effectiveness of 2 Gy fractionated radiotherapy and identifies Enox1 as a potential therapeutic target. PMID:27788492

  9. Three years of Swift/BAT Survey of AGN: Reconciling Theory and Observations?

    SciTech Connect

    Burlon, D.; Ajello, M.; Greiner, J.; Comastri, A.; Merloni, A.; Gehrels, N.; /NASA, Goddard

    2011-02-07

    It is well accepted that unabsorbed as well as absorbed AGN are needed to explain the nature and the shape of the Cosmic X-ray background, even if the fraction of highly absorbed objects (dubbed Compton-thick sources) substantially still escapes detection. We derive and analyze the absorption distribution using a complete sample of AGN detected by Swift-BAT in the first three years of the survey. The fraction of Compton-thick AGN represents only 4.6% of the total AGN population detected by Swift-BAT. However, we show that once corrected for the bias against the detection of very absorbed sources the real intrinsic fraction of Compton-thick AGN is 20{sub -6}{sup +9}%. We proved for the first time (also in the BAT band) that the anti-correlation of the fraction of absorbed AGN and luminosity it tightly connected to the different behavior of the luminosity functions (XLFs) of absorbed and unabsorbed AGN. This points towards a difference between the two subsamples of objects with absorbed AGN being, on average, intrinsically less luminous than unobscured ones. Moreover the XLFs show that the fraction of obscured AGN might also decrease at very low luminosity. This can be successfully interpreted in the framework of a disk cloud outflow scenario as the disappearance of the obscuring region below a critical luminosity. Our results are discussed in the framework of population synthesis models and the origin of the Cosmic X-ray Background.

  10. Properties of galaxies around AGNs with the most massive supermassive black holes revealed by clustering analysis

    NASA Astrophysics Data System (ADS)

    Shirasaki, Yuji; Komiya, Yutaka; Ohishi, Masatoshi; Mizumoto, Yoshihiko

    2016-04-01

    We present results of the clustering analysis between active galactic nuclei (AGNs) and galaxies at redshift 0.1-1.0, which was performed to investigate the properties of galaxies associated with the AGNs and reveal the nature of the fueling mechanism of supermassive black holes (SMBHs). We used 8059 AGNs/quasi-stellar objects (QSOs) for which virial masses of individual SMBHs were measured, and divided them into four mass groups.Cross-correlation analysis was performed to reconfirm our previous result that cross-correlation length increases with SMBH mass MBH; we obtained consistent results. A linear bias of AGN for each mass group was measured as 1.47 for MBH = 107.5-108.2 M⊙ and 3.08 for MBH = 109-1010 M⊙. The averaged color and luminosity distributions of galaxies around the AGNs/QSOs were also derived for each mass group. The galaxy color Dopt-IR was estimated from a spectral energy distribution (SED) constructed from a catalog derived by merging the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS) catalogs. The distributions of color and luminosity were derived by a subtraction method, which does not require redshift information of galaxies. The main results of this work are as follows. (1) A linear bias increases by a factor of two from the lower-mass group to the highest-mass group. (2) The environment around AGNs with the most massive SMBHs (MBH > 109 M⊙) is dominated by red sequence galaxies. (3) Marginal indication of decline in luminosity function at dimmer side of MIR > -19.5 is found for galaxies around AGNs with MBH = 108.2-109 M⊙ and nearest redshift group (z = 0.1-0.3). These results indicate that AGNs with the most massive SMBHs reside in haloes where a large fraction of galaxies have been transited to the red sequence. The accretion of hot halo gas as well as recycled gas from evolving stars can be one of the plausible mechanisms to fuel the SMBHs above ˜ 109 M⊙.

  11. Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction

    NASA Astrophysics Data System (ADS)

    Raupach, M. R.; Canadell, J. G.; Le Quéré, C.

    2008-11-01

    We quantify the relative roles of natural and anthropogenic influences on the growth rate of atmospheric CO2 and the CO2 airborne fraction, considering both interdecadal trends and interannual variability. A combined ENSO-Volcanic Index (EVI) relates most (~75%) of the interannual variability in CO2 growth rate to the El-Niño-Southern-Oscillation (ENSO) climate mode and volcanic activity. Analysis of several CO2 data sets with removal of the EVI-correlated component confirms a previous finding of a detectable increasing trend in CO2 airborne fraction (defined using total anthropogenic emissions including fossil fuels and land use change) over the period 1959 2006, at a proportional growth rate 0.24% y-1 with probability ~0.9 of a positive trend. This implies that the atmospheric CO2 growth rate increased slightly faster than total anthropogenic CO2 emissions. To assess the combined roles of the biophysical and anthropogenic drivers of atmospheric CO2 growth, the increase in the CO2 growth rate (1.9% y-1 over 1959 2006) is expressed as the sum of the growth rates of four global driving factors: population (contributing +1.7% y-1); per capita income (+1.8% y-1); the total carbon intensity of the global economy (-1.7% y-1); and airborne fraction (averaging +0.2% y-1 with strong interannual variability). The first three of these factors, the anthropogenic drivers, have therefore dominated the last, biophysical driver as contributors to accelerating CO2 growth. Together, the recent (post-2000) increase in growth of per capita income and decline in the negative growth (improvement) in the carbon intensity of the economy will drive a significant further acceleration in the CO2 growth rate over coming decades, unless these recent trends reverse.

  12. Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm

    SciTech Connect

    Stawarz, L.; Sikora, M.; Lasota, J.-P.

    2007-10-15

    We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. We find that AGNs form two distinct and well separated sequences on the radio-loudness -- Eddington-ratio plane. We argue that these sequences mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that another parameter in addition to the accretion rate must play a role in determining the jet production efficiency in active galactic nuclei, and that this parameter is related to properties of the host galaxy. The revealed host-related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. We argue that the huge difference between the radio-loudness reachable by AGNs in disc and elliptical galaxies can be explained by the scenario according to which the spin of a black hole determines the outflows power, and central black holes can reach large spins only in early type galaxies (following major mergers), and not (in a statistical sense) in spiral galaxies.

  13. Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

    NASA Technical Reports Server (NTRS)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-01-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  14. Exploring Quenching, Morphological Transformation and AGN-Driven Winds with Simulations of Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Brennan, Ryan; CANDELS

    2017-01-01

    We present an examination of the spheroid growth and star formation quenching experienced by galaxies since z~3 by studying the evolution with redshift of the quiescent and spheroid-dominated fractions of galaxies from the CANDELS and GAMA surveys. We compare these fractions with predictions from a semi-analytic model which includes prescriptions for bulge growth and AGN feedback due to mergers and disk instabilities. We then subdivide our population into the four quadrants of the specific star-formation rate (sSFR)-Sersic index plane. We find that the fraction of star forming disks declines steadily while the fraction of quiescent spheroids increases with cosmic time. The fraction of star-forming spheroids and quiescent disks are both non-negligible and remain nearly constant. Our model is qualitatively successful at reproducing these fractions, suggesting a plausible explanation for the observed correlations between star formation activity and galaxy structure.Next, we study the correlation of galaxy structural properties with their location relative to the star-formation rate-stellar mass correlation, or the star forming main sequence. We find that as we move from observed galaxies above the main sequence to those below it, we see a nearly monotonic trend towards higher median Sersic index, smaller radius, lower SFR density and higher stellar mass density. Our model again qualitatively reproduces these trends, supporting a picture in which bulges and black holes co-evolve and AGN feedback plays a critical role in galaxy quenching.Finally, we examine AGN-driven winds in a suite of cosmological zoom simulations including a novel mechanical and radiation-driven AGN feedback prescription and compare the gas cycle with a matched suite of zoom simulations that include only feedback from supernovae and young stars. We find that while stellar feedback can drive mass out of galaxies, it is unlikely to be able to keep the gas from re-accreting, whereas in our AGN runs it

  15. Black hole growth and starburst activity at z = 0.6-4 in the Chandra Deep Field South. Host galaxies properties of obscured AGN

    NASA Astrophysics Data System (ADS)

    Brusa, M.; Fiore, F.; Santini, P.; Grazian, A.; Comastri, A.; Zamorani, G.; Hasinger, G.; Merloni, A.; Civano, F.; Fontana, A.; Mainieri, V.

    2009-12-01

    Aims: The co-evolution of host galaxies and the active black holes which reside in their centre is one of the most important topics in modern observational cosmology. Here we present a study of the properties of obscured active galactic nuclei (AGN) detected in the CDFS 1 Ms observation and their host galaxies. Methods: We limited the analysis to the MUSIC area, for which deep K-band observations obtained with ISAAC@VLT are available, ensuring accurate identifications of the counterparts of the X-ray sources as well as reliable determination of photometric redshifts and galaxy parameters, such as stellar masses and star formation rates. In particular, we: 1) refined the X-ray/infrared/optical association of 179 sources in the MUSIC area detected in the Chandra observation; 2) studied the host galaxies observed and rest frame colors and properties. Results: We found that X-ray selected (LX ⪆ 1042 erg s-1) AGN show Spitzer colors consistent with both AGN and starburst dominated infrared continuum; the latter would not have been selected as AGN from infrared diagnostics. The host galaxies of X-ray selected obscured AGN are all massive (Mast > 1010 M_⊙) and, in 50% of the cases, are also actively forming stars (1/SSFR < tHubble) in dusty environments. The median L/LEdd value of the active nucleus is between 2% and 10% depending on the assumed MBH/Mast ratio. Finally, we found that the X-ray selected AGN fraction increases with the stellar mass up to a value of 30% at z > 1 and Mast > 3 × 1011 M_⊙, a fraction significantly higher than in the local Universe for AGN of similar luminosities. Tables [see full textsee full textsee full text] and [see full textsee full textsee full text] are only available in electronic form at http://www.aanda.org

  16. Modification by fractionation distillation to increase the quality of Biosolar as same as Pertamina Dex

    NASA Astrophysics Data System (ADS)

    Nugraheni, Ika Kusuma; Triyono

    2017-03-01

    This research studies the modification of Biosolar to have a similar quality with Pertamina Dex. Pertamina Dex is known as the best diesel fuel in Indonesia. Pertamina Dex is made from fossil petroleum like another diesel fuel. The different of Pertamina Dex with another diesel fuel is quality of this fuel is better than another. With a good quality, the price of Pertamina Dex is also higher than another fuel. The composition of fuel can determine the fuels quality. But until now, the specific composition of Pertamina Dex does not publish. Beside Pertamina Dex, another diesel fuel that commonly used in Indonesia is Biosolar. Biosolar consist of 90% of petroleum and 10% of Biodiesel. Biosolar subsidized by the government, so the price of this diesel fuel has a lower cost. This research was conducted to study how a Biosolar as Diesel Fuel can has a similar characteristic with Pertamina Dex that has a good quality. Modification with eliminating components was done by distillation. This modification makes Biosolar has similar component's spread with Pertamina Dex. The similarity in component's spread has a probability that both of fuel has a similar component. In gas chromatography results show that modification by distillation method make Biosolar has a similar retention time with Pertamina Dex. But in characteristic test still has a few differences in calorie and density, and still different in viscosity value. The values are; density: 842.5 kg/m3 (Pertamina Dex), 838.5 kg/m3 (fraction of Biosolar), calorie: 11303.63 Cal/g (Pertamina Dex), 11255.67 Cal/g (Biosolar fraction) and viscosity: 7.37 mm2/s (Pertamina Dex), 5.28 mm2/s (Biosolar fraction). The characteristic results show that modification Biosolar with eliminating components by distillation can increase the characteristic of Biosolar, but did not have a similar characteristic with Pertamina Dex yet.

  17. Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction

    NASA Astrophysics Data System (ADS)

    Raupach, M. R.; Canadell, J. G.; Le Quéré, C.

    2008-07-01

    We quantify the relative roles of natural and anthropogenic influences on the growth rate of atmospheric CO2 and the CO2 airborne fraction, considering both interdecadal trends and interannual variability. A combined ENSO-Volcanic Index (EVI) relates most (~75%) of the interannual variability in CO2 growth rate to the El-Niño-Southern-Oscillation (ENSO) climate mode and volcanic activity. Analysis of several CO2 data sets with removal of the EVI-correlated component confirms a previous finding of a detectable increasing trend in CO2 airborne fraction (defined using total anthropogenic emissions including fossil fuels and land use change) over the period 1959 2006, at a proportional growth rate 0.24% y-1 with probability ~0.9 of a positive trend. This implies that the atmospheric CO2 growth rate increased slightly faster than total anthropogenic CO2 emissions. An extended form of the Kaya identity relates the increase in the CO2 growth rate (1.9% y-1 over 1959 2006) to the growth rates of four global driving factors: population (contributing +1.7% y-1); per capita income (+1.8% y-1); the total carbon intensity of the global economy (-1.7% y-1); and airborne fraction (averaging +0.2% y-1 with strong interannual variability). Together, the recent (post-2000) increase in growth of per capita income and decline in the negative growth (improvement) in the carbon intensity of the economy will drive a significant acceleration in the CO2 growth rate over coming decades, unless these recent trends reverse. To achieve an annual reduction rate in total emissions of -2% y-1 (which would halve emissions in 35 years) in the presence of a per-capita income growth rate of 2% y-1 and a population growth rate of 1% y-1, it is necessary to achieve a decline in total carbon intensity of the economy at a rate of around -5% y-1, three times the 1959 2006 average.

  18. Pressure drop of slug flow in microchannels with increasing void fraction: experiment and modeling.

    PubMed

    Molla, Shahnawaz; Eskin, Dmitry; Mostowfi, Farshid

    2011-06-07

    Pressure drop in a gas-liquid slug flow through a long microchannel of rectangular cross-section was investigated. Pressure measurements in a lengthy (∼0.8 m) microchannel determined the pressure gradient to be constant in a flow where gas bubbles progressively expanded and the flow velocity increased due to a significant pressure drop. Most of the earlier studies of slug flow in microchannels considered systems where the expansion of the gas bubbles was negligible in the channel. In contrast, we investigated systems where the volume of the gas phase increased significantly due to a large pressure drop (up to 1811 kPa) along the channel. This expansion of the gas phase led to a significant increase in the void fraction, causing considerable flow acceleration. The pressure drop in the microchannel was studied for three gas-liquid systems; water-nitrogen, dodecane-nitrogen, and pentadecane-nitrogen. Inside the microchannel, local pressure was measured using a series of embedded membranes acting as pressure sensors. Our investigation of the pressure drop showed a linear trend over a wide range of void fractions and flow conditions in the two-phase flow. The lengths and the velocities of the liquid slugs and the gas bubbles were also studied along the microchannel by employing a video imaging technique. Furthermore, a model describing the gas-liquid slug flow in a long microchannel was developed to calculate the pressure drop under conditions similar to the experiments. An excellent agreement between the developed model and the experimental data was obtained.

  19. Incidence of WISE-Selected Obscured AGNs in Major Mergers and Interactions from the SDSS

    NASA Astrophysics Data System (ADS)

    Weston, Madalyn; McIntosh, Daniel H.; Brodwin, Mark; Mann, Justin; Cooper, Andrew; McConnell, Adam; Nielson, Jennifer L.

    2017-01-01

    We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z≤0.08) catalog of visually-selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2×10^10 M⊙, we find that major mergers (interactions) are 5--17 (3--5) times more likely to have red [3.4]-[4.6] colors associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fiber spectral diagnostics, we map the [3.4]-[4.6] versus [4.6]-[12] colors of different emission-line galaxies and find one-quarter of Seyferts have colors indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star-forming and located at the centers of Mhalo<10^13 M⊙ groups. Assuming plausibly short duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations. We will use the WISE-selected AGNs (and AGNs selected by other methods) to perform SED analysis of mergers and interactions and dissect the SEDs to disentangle AGN and SF activity.

  20. Measuring Feedback in Nearby AGN

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Fischer, T. C.; Kraemer, S. B.; Schmitt, H. R.; Turner, T. J.

    2012-08-01

    We investigate the impact of feedback from outflowing UV and X-ray absorbers in nearby (z < 0.04) AGN. From studies of the kinematics, physical conditions, and variability of the absorbers in the literature, we calculate the possible ranges in total mass outflow rate (Ṁout) and kinetic luminosity (LK) for each AGN, summed over all of the absorbers. These calculations make use of values (or limits) for the radial locations of the absorbers determined from variability, excited-state absorption, or other considerations. From a sample of 10 Seyfert 1 galaxies with detailed photoionization models for their absorbers, we find that 7 have sufficient constraints on the absorber locations to determine Ṁout and LK. The 6 Seyfert 1s with moderate bolometric luminosities (Lbol = 1043 - 1045 ergs s-1) all have mass outflow rates that are 10 - 1000 times the mass accretion rates needed to generate their observed luminosities, indicating that most of the mass outflow originates from outside the inner accretion disk. Three of these (NGC 4051, NGC 3516, and NGC 3783) have LK in the range 0.5 - 5% Lbol, which is the range typically required by feedback models for efficient self-regulation of black-hole and galactic bulge growth. The other three (NGC 5548, NGC 4151, and NGC 7469) have LK > 0.1%Lbol, although these values may increase if radial locations can be determined for more of the absorbers. We conclude that the outflowing UV and X-ray absorbers in moderate-luminosity AGN have the potential to deliver significant feedback to their environments.

  1. Clouds Aerosols Internal Affaires: Increasing Cloud Fraction and Enhancing the Convection

    NASA Technical Reports Server (NTRS)

    Koren, Ilan; Kaufman, Yoram; Remer, Lorraine; Rosenfeld, Danny; Rudich, Yinon

    2004-01-01

    Clouds developing in a polluted environment have more numerous, smaller cloud droplets that can increase the cloud lifetime and liquid water content. Such changes in the cloud droplet properties may suppress low precipitation allowing development of a stronger convection and higher freezing level. Delaying the washout of the cloud water (and aerosol), and the stronger convection will result in higher clouds with longer life time and larger anvils. We show these effects by using large statistics of the new, 1km resolution data from MODIS on the Terra satellite. We isolate the aerosol effects from meteorology by regression and showing that aerosol microphysical effects increases cloud fraction by average of 30 presents for all cloud types and increases convective cloud top pressure by average of 35mb. We analyze the aerosol cloud interaction separately for high pressure trade wind cloud systems and separately for deep convective cloud systems. The resultant aerosol radiative effect on climate for the high pressure cloud system is: -10 to -13 W/sq m at the top of the atmosphere (TOA) and -11 to -14 W/sq m at the surface. For deeper convective clouds the forcing is: -4 to -5 W/sq m at the TOA and -6 to -7 W/sq m at the surface.

  2. AGN Coronae through a Jet Perspective

    NASA Astrophysics Data System (ADS)

    King, Ashley L.; Lohfink, Anne; Kara, Erin

    2017-02-01

    This paper presents an in-depth look at the jet and coronal properties of 41 active galactic nuclei (AGNs). Utilizing the highest quality NuSTAR, XMM-Newton, and NRAO VLA Sky Survey 1.4 GHz data, we find that the radio Eddington luminosity inversely scales with X-ray reflection fraction, and positively scales with the distance between the corona and the reflected regions in the disk. We next investigate a model fit to the data that predicts the corona is outflowing and propagates into the large-scale jet. We find this model describes the data well and predicts that the corona has mildly relativistic velocities, 0.04< β < 0.40. We discuss our results in the context of disk–jet connections in AGNs.

  3. Enlarged thalamic volumes and increased fractional anisotropy in the thalamic radiations in veterans with suicide behaviors.

    PubMed

    Lopez-Larson, Melissa; King, Jace B; McGlade, Erin; Bueler, Elliott; Stoeckel, Amanda; Epstein, Daniel J; Yurgelun-Todd, Deborah

    2013-01-01

    Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB + SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI + SB versus HC and (2) TBI + SB versus combined HC and TBI-SB and (3) between TBI + SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI + SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI + SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI + SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI + SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide.

  4. Enlarged Thalamic Volumes and Increased Fractional Anisotropy in the Thalamic Radiations in Veterans with Suicide Behaviors

    PubMed Central

    Lopez-Larson, Melissa; King, Jace B.; McGlade, Erin; Bueler, Elliott; Stoeckel, Amanda; Epstein, Daniel J.; Yurgelun-Todd, Deborah

    2013-01-01

    Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB + SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI + SB versus HC and (2) TBI + SB versus combined HC and TBI-SB and (3) between TBI + SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI + SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI + SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI + SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI + SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide. PMID:23964245

  5. Toward a Unified AGN Structure

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes; Fukumura, Keigo; Shrader, Chris; Behar, Ehud; Contopoulosa, Ioannis

    2012-01-01

    We present a unified model for the structure and appearance of accretion powered sources across their entire luminosity range from galactic X-ray binaries (XRB) to luminous quasars, with emphasis on AG N and their phenomenology. Central to this model is the notion of MHD winds launched by the accretion disks that power these objects. These winds provide the matter that manifests as blueshifted absorption features in the UV and X-ray spectra of a large fraction of these sources; furthermore, their density distribution in the poloidal plane determines their "appearance" (i.e. the column and velocity structure of these absorption features and the obscuration of the continuum source) as a function of the observer inclination angle (a feature to which INTEGRAL has made significant contributions). This work focuses on just the broadest characteristics of these objects; nonetheless, it provides scaling laws that allow one to reproduce within this model the properties of objects extending in luminosity from luminous quasars to XRBs. Our general conclusion is that the AGN phenomenology can be accounted for in terms of three parameters: The wind maSS flux in units of the Eddington value, m(dot), the observers' inclination angle Theta and the logarithmic slope between the 0/UV and X-ray fluxes alpha(sub ox); however because of a correlation between alpha(sub ox) and UV luminosity the number of significant parameters is two. The AGN correlations implied by this model appear to extend to and consistent with the XRB phenomenology, suggesting the presence of a truly unified underlying structure for accretion powered sources.

  6. Ionized Absorbers in AGN

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

    As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

  7. Lyman continuum leaking AGN in the SSA22 field

    NASA Astrophysics Data System (ADS)

    Micheva, Genoveva; Iwata, Ikuru; Inoue, Akio K.

    2017-02-01

    Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin nature or are foreground contaminants. The remaining two LyC candidates are type I AGN. We argue that the average LyC escape fraction of high-redshift, low-luminosity AGN is not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of 2 lower than values obtained assuming fesc = 1. Comparing to recent Ly α forest measurements, AGNs at redshift z ˜ 3 make up at most ˜12 per cent and as little as ˜5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

  8. Revisiting the Structure and Spectrum of the Magnetic-reconnection-heated Corona in Luminous AGNs

    NASA Astrophysics Data System (ADS)

    Liu, J. Y.; Qiao, E. L.; Liu, B. F.

    2016-12-01

    It is believed that the hard X-ray emission in the luminous active galactic nuclei (AGNs) is from the hot corona above the cool accretion disk. However, the formation of the corona is still debated. Liu et al. investigated the spectrum of the corona heated by the reconnection of the magnetic field generated by dynamo action in the thin disk and emerging into the corona as a result of buoyancy instability. In the present paper, we improve this model to interpret the observed relation of the hard X-ray spectrum becoming softer at higher accretion rate in luminous AGNs. The magnetic field is characterized by {β }0, i.e., the ratio of the sum of gas pressure and radiation pressure to the magnetic pressure in the disk ({β }0=({P}g,d+{P}r,d)/{P}B). Besides, both the intrinsic disk photons and reprocessed photons by the disk are included as the seed photons for inverse Compton scattering. These improvements are crucial for investigating the effect of magnetic field on the accretion disk corona when it is not clear whether the radiation pressure or gas pressure dominates in the thin disk. We change the value of {β }0 in order to constrain the magnetic field in the accretion disk in luminous AGNs. We find that the energy fraction released in the corona (f) gradually increases with the decrease of {β }0 for the same accretion rate. When {β }0 decreases to less than 50, the structure and spectrum of the disk corona are independent of accretion rate, which is similar to the hard spectrum found in Liu et al. Comparing with the observational results of the hard X-ray bolometric correction factor in a sample of luminous AGNs, we suggest that the value of {β }0 is about 100-200 for α = 0.3, and the energy fraction f should be larger than 30% for hard X-ray emission.

  9. Starburst or AGN dominance in submm-luminous candidate AGN

    NASA Astrophysics Data System (ADS)

    Coppin, Kristen; Alexander, Dave; Aretxaga, Itziar; Blain, Andrew; Chapman, Scott; Clements, Dave; Dunlop, James; Dunne, Loretta; Dye, Simon; Farrah, Duncan; Hughes, David; Ivison, Rob; Kim, Sungeun; Menendez-Delmestre, Karin; Oliver, Sebastian; Page, Mat; Pope, Alexandra; Rowan-Robinson, Michael; Scott, Douglas; Smail, Ian; Swinbank, Mark; Vaccari, Mattia; van Kampen, Eelco

    2008-03-01

    It is widely believed that starbursts/ULIRGs and AGN activity are triggered by galaxy interactions and merging; and sub-mm selected galaxies (SMGs) seem to be simply high redshift ULIRGs, observed near the peak of activity. In this evolutionary picture every SMG would host an AGN, which would eventually grow a black hole strong enough to blow off all of the gas and dust leaving an optically luminous QSO. In order to probe this evolutionary sequence, a crucial sub-sample to focus on would be the 'missing link' sources, which demonstrate both strong starburst and AGN signatures and to determine if the starburst is the main power source even in SMGs when we have evidence that an AGN is present. The best way to determine if a dominant AGN is present is to look in the mid-IR for their signatures, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We have selected a sample of SMGs which are good candidates for harboring powerful AGN on the basis of their IRAC colours (S8um/S4.5um>2). Once we confirm these SMGs are AGN-dominated, we can then perform an audit of the energy balance between star-formation and AGN within this special sub-population of SMGs where the BH has grown appreciably to begin heating the dust emission. The proposed observations with IRS will probe the physics of how SMGs evolve from a cold-dust starburst-dominated ULIRG to an AGN/QSO by measuring the level of the mid-IR continuum, PAH luminosity, and Si absorption in these intermediate `transitory' AGN/SMGs.

  10. [Ultra] luminous infrared galaxies selected at 90 μm in the AKARI deep field: a study of AGN types contributing to their infrared emission

    NASA Astrophysics Data System (ADS)

    Małek, K.; Bankowicz, M.; Pollo, A.; Buat, V.; Takeuchi, T. T.; Burgarella, D.; Goto, T.; Malkan, M.; Matsuhara, H.

    2017-01-01

    Aims: The aim of this work is to characterize physical properties of ultra luminous infrared galaxies (ULIRGs) and luminous infrared galaxies (LIRGs) detected in the far-infrared (FIR) 90 μm band in the AKARI Deep Field-South (ADF-S) survey. In particular, we want to estimate the active galactic nucleus (AGN) contribution to the LIRGs and ULIRGs' infrared emission and which types of AGNs are related to their activity. Methods: We examined 69 galaxies at redshift ≥0.05 detected at 90 μm by the AKARI satellite in the ADF-S, with optical counterparts and spectral coverage from the ultraviolet to the FIR. We used two independent spectral energy distribution fitting codes: one fitting the SED from FIR to FUV (CIGALE) (we use the results from CIGALE as a reference) and gray-body + power spectrum fit for the infrared part of the spectra (CMCIRSED) in order to identify a subsample of ULIRGs and LIRGs, and to estimate their properties. Results: Based on the CIGALE SED fitting, we have found that LIRGs and ULIRGs selected at the 90 μm AKARI band compose 56% of our sample (we found 17 ULIRGs and 22 LIRGs, spanning over the redshift range 0.06 AGN contribution to the mid-infrared luminosity for 63% of LIRGs and ULIRGs. Our LIRGs contain Type 1, Type 2, and intermediate types of AGN, whereas for ULIRGs, a majority (more than 50%) of AGN emission originates from Type 2 AGNs. The temperature-luminosity and temperature-mass relations for the dust component of ADF-S LIRGs and ULIRGs indicate that these relations are shaped by the dust mass and not by the increased dust heating. Conclusions: We conclude that LIRGs contain Type 1, Type 2, and intermediate types of AGNs, with an AGN contribution to the mid infrared emission at the median level of 13 ± 3

  11. The relative wavelength independence of IR lags in AGNs: implications for the distribution of the hot dust

    NASA Astrophysics Data System (ADS)

    Oknyansky, V.

    2015-09-01

    As seen from the central source, the dusty torus of AGNs has a puzzlingly high covering factor. If the torus consists of clouds of dust, each with a relatively unobscured view of the higher energy photons from nearer the center of the AGN, the temperature of each dust cloud will fall off as roughly the inverse square root of the radius. Since the dust is heated by the central radiation, in such a model the Near and Mid IR lag would increase with the wavelength to a power of 2 to 2.8. We show that, contrary to this simple prediction, for a significant fraction of AGNs the lags of the J, H, K, and L bands with respect to the optical show at best only a small difference. This means that rather than there being an extended radial temperature gradient, the hot dust reprocessing the central radiation is effectively in a relatively thin shell. We show that this can be explained by the hot dust being on the surface of a cone that is approximately tangential to the paraboloidal isodelay surface. We note that a number of the AGNs showing similar J, H, K, and L lags are also Seyferts that have changed between type 1 and type 2. It is not clear whether this is related or is merely a consequence of these objects being well studied for a long time.

  12. Right ventricular ejection fraction: an indicator of increased mortality in patients with congestive heart failure associated with coronary artery disease

    SciTech Connect

    Polak, J.F.; Holman, B.L.; Wynne, J.; Colucci, W.S.

    1983-08-01

    The predictive value of radionuclide ventriculography was studied in 34 patients with depressed left ventricular ejection fraction (less than 40%) and clinically evident congestive heart failure secondary to atherosclerotic coronary artery disease. In addition to left ventricular ejection fraction, right ventricular ejection fraction and extent of left ventricular paradox were obtained in an attempt to identify a subgroup at increased risk of mortality during the ensuing months. The 16 patients who were alive after a 2 year follow-up period had a higher right ventricular ejection fraction and less extensive left ventricular dyskinesia. When a right ventricular ejection fraction of less than 35% was used as a discriminant, mortality was significantly greater among the 21 patients with a depressed right ventricular ejection fraction (71 versus 23%), a finding confirmed by a life table analysis. It appears that the multiple factors contributing to the reduction in right ventricular ejection fraction make it a useful index not only for assessing biventricular function, but also for predicting patient outcome.

  13. Obscured accretion from AGN surveys

    NASA Astrophysics Data System (ADS)

    Vignali, Cristian

    2014-07-01

    Recent models of super-massive black hole (SMBH) and host galaxy joint evolution predict the presence of a key phase where accretion, traced by obscured Active Galactic Nuclei (AGN) emission, is coupled with powerful star formation. Then feedback processes likely self-regulate the SMBH growth and quench the star-formation activity. AGN in this important evolutionary phase have been revealed in the last decade via surveys at different wavelengths. On the one hand, moderate-to-deep X-ray surveys have allowed a systematic search for heavily obscured AGN, up to very high redshifts (z~5). On the other hand, infrared/optical surveys have been invaluable in offering complementary methods to select obscured AGN also in cases where the nuclear X-ray emission below 10 keV is largely hidden to our view. In this review I will present my personal perspective of the field of obscured accretion from AGN surveys.

  14. New Insights on the Accretion Disk-Winds Connection in Radio-Loud AGNs from Suzaku

    NASA Technical Reports Server (NTRS)

    Tombesi, F.; Sambruna, R. M.; Reeves, J. N.; Braito, V.; Cappi, M.; Reynolds, S.; Mushotzky, R. F.

    2011-01-01

    From the spectral analysis of long Suzaku observations of five radio-loud AGNs we have been able to discover the presence of ultra-fast outflows with velocities ,,approx.0.1 c in three of them, namely 3C III, 3C 120 and 3C 390.3. They are consistent with being accretion disk winds/outflows. We also performed a follow-up on 3C III to monitor its outflow on approx.7 days time-scales and detected an anti-correlated variability of a possible relativistic emission line with respect to blue-shifted Fe K features, following a flux increase. This provides the first direct evidence for an accretion disc-wind connection in an AGN. The mass outflow rate of these outflows can be comparable to the accretion rate and their mechanical power can correspond to a significant fraction of the bolometric luminosity and is comparable to their typical jet power. Therefore, they can possibly play a significant role in the expected feedback from AGNs and can give us further clues on the relation between the accretion disk and the formation of winds/jets.

  15. Starburst or AGN Dominance in Submillimetre-Luminous Candidate AGN?

    NASA Astrophysics Data System (ADS)

    Coppin, Kristen; Pope, Alexandra; Menéndez-Delmestre, Karín; Alexander, David M.; Dunlop, James

    2010-06-01

    It is widely believed that ultraluminous infrared (IR) galaxies and active galactic nuclei (AGN) activity are triggered by galaxy interactions and merging, with the peak of activity occurring at z~2, where submillimetre galaxies are thousands of times more numerous than local ULIRGs. In this evolutionary picture, submillimetre galaxies (SMGs) would host an AGN, which would eventually grow a black hole (BH) strong enough to blow off all of the gas and dust leaving an optically luminous QSO. To probe this evolutionary sequence we have focussed on the `missing link' sources, which demonstrate both strong starburst (SB) and AGN signatures, in order to determine if the SB is the main power source even in SMGs when we have evidence that an AGN is present from their IRAC colours. The best way to determine if a dominant AGN is present is to look for their signatures in the mid-infrared with the Spitzer IRS, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We present the results of our audit of the energy balance between star-formation and AGN within this special sub-population of SMGs-where the BH has grown appreciably to begin heating the dust emission.

  16. PRIMUS: The Dependence of AGN Accretion on Host Stellar Mass and Color

    NASA Astrophysics Data System (ADS)

    Aird, James; Coil, Alison L.; Moustakas, John; Blanton, Michael R.; Burles, Scott M.; Cool, Richard J.; Eisenstein, Daniel J.; Smith, M. Stephen M.; Wong, Kenneth C.; Zhu, Guangtun

    2012-02-01

    We present evidence that the incidence of active galactic nuclei (AGNs) and the distribution of their accretion rates do not depend on the stellar masses of their host galaxies, contrary to previous studies. We use hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS, COSMOS, and ELAIS-S1) with redshifts from the Prism Multi-object Survey to identify 242 AGNs with L 2-10 keV = 1042-44 erg s-1 within a parent sample of ~25,000 galaxies at 0.2 < z < 1.0 over ~3.4 deg2 and to i ~ 23. We find that although the fraction of galaxies hosting an AGN at fixed X-ray luminosity rises strongly with stellar mass, the distribution of X-ray luminosities is independent of mass. Furthermore, we show that the probability that a galaxy will host an AGN can be defined by a universal Eddington ratio distribution that is independent of the host galaxy stellar mass and has a power-law shape with slope -0.65. These results demonstrate that AGNs are prevalent at all stellar masses in the range 9.5 and that the same physical processes regulate AGN activity in all galaxies in this stellar mass range. While a higher AGN fraction may be observed in massive galaxies, this is a selection effect related to the underlying Eddington ratio distribution. We also find that the AGN fraction drops rapidly between z ~ 1 and the present day and is moderately enhanced (factor ~2) in galaxies with blue or green optical colors. Consequently, while AGN activity and star formation appear to be globally correlated, we do not find evidence that the presence of an AGN is related to the quenching of star formation or the color transformation of galaxies.

  17. X-ray spectral properties of the AGN sample in the northern XMM-XXL field

    NASA Astrophysics Data System (ADS)

    Liu, Zhu; Merloni, Andrea; Georgakakis, Antonis; Menzel, Marie-Luise; Buchner, Johannes; Nandra, Kirpal; Salvato, Mara; Shen, Yue; Brusa, Marcella; Streblyanska, Alina

    2016-06-01

    In this paper we describe and publicly release a catalogue consisting of 8445 point-like X-ray sources detected in the XMM-XXL north survey. For the 2512 AGN which have reliable spectroscopy from SDSS-III/BOSS, we present the X-ray spectral fitting which has been computed with a Bayesian approach. We have also applied an X-ray spectral stacking method to different sub-samples, selected on the basis of the AGN physical properties (L2-10 keV, z, MBH, λEdd and NH). We confirm the well-known Iwasawa-Taniguchi effect in our luminosity-redshift sub-samples, and argue that such an effect is due to a decrease in the covering factor of a distant obscuring `torus' with increasing X-ray luminosity. By comparing the distribution of the reflection fraction, the ratio of the normalization of the reflected component to the direct radiation, we find that the low-luminosity, low-redshift sub-sample had systematically higher reflection fraction values than the high-redshift, high-luminosity one. On the other hand, no significant difference is found between samples having similar luminosity but different redshift, suggesting that the structure of the torus does not evolve strongly with redshift. Contrary to previous works, we do not find evidence for an increasing photon index at high Eddington ratio. This may be an indication that the structure of the accretion disc changes as the Eddington ratio approaches unity. Comparing our X-ray spectral analysis results with the optical spectral classification, we find that ˜20 per cent of optical type-1 AGN show an X-ray absorbing column density higher than 1021.5 cm- 2, and about 50 per cent of type-2 AGN have an X-ray absorbing column density less than 1021.5 cm- 2. We suggest that the excess X-ray absorption shown in the high-luminosity optical type-1 AGN can be due to small-scale dust-free gas within (or close to) the broad-line region, while in the low-luminosity ones it can be due to a clumpy torus with a large covering factor.

  18. Time-Dependent Photoionization of Gas Outflows in AGN

    NASA Astrophysics Data System (ADS)

    Elhoussieny, Ehab E.; Bautista, M.; Garcia, J.; Kallman, T. R.

    2013-01-01

    Gas outflows are fundamental components of Active Galactic Nuclei (AGN) activity. Time-variability of ionizing radiation, which is characteristic of AGN in various different time scales, may produce non-equilibrium photoionization conditions over a significant fraction of the flow and yields supersonically moving cooling/heating fronts. These fast fronts create pressure imbalances that can only be resolved by fragmentation of the flow and acceleration of such fragments. This mechanism can explain the kinematic structure of low ionization BAL systems (FeLoBAL). This mechanism may also have significant effects on other types of outflows given the wide range of variability time scales in AGN. We will study these effects in detail by constructing time-dependent photoionization models of the outflows and incorporating these models into radiative-hydrodynamic simulations.

  19. THE SPATIAL CLUSTERING OF ROSAT ALL-SKY SURVEY AGNs. II. HALO OCCUPATION DISTRIBUTION MODELING OF THE CROSS-CORRELATION FUNCTION

    SciTech Connect

    Miyaji, Takamitsu; Aceves, Hector; Krumpe, Mirko; Coil, Alison L.

    2011-01-10

    This is the second paper of a series that reports on our investigation of the clustering properties of active galactic nuclei (AGNs) in the ROSAT All-Sky Survey (RASS) through cross-correlation functions (CCFs) with Sloan Digital Sky Survey (SDSS) galaxies. In this paper, we apply the Halo Occupation Distribution (HOD) model to the CCFs between the RASS broad-line AGNs with SDSS luminous red galaxies (LRGs) in the redshift range 0.16 < z < 0.36 that was calculated in Paper I. In our HOD modeling approach, we use the known HOD of LRGs and constrain the HOD of the AGNs by a model fit to the CCF. For the first time, we are able to go beyond quoting merely a 'typical' AGN host halo mass, M{sub h}, and model the full distribution function of AGN host dark matter halos. In addition, we are able to determine the large-scale bias and the mean M{sub h} more accurately. We explore the behavior of three simple HOD models. Our first model (Model A) is a truncated power-law HOD model in which all AGNs are satellites. With this model, we find an upper limit to the slope ({alpha}) of the AGN HOD that is far below unity. The other two models have a central component, which has a step function form, where the HOD is constant above a minimum mass, without (Model B) or with (Model C) an upper mass cutoff, in addition to the truncated power-law satellite component, similar to the HOD that is found for galaxies. In these two models we find that the upper limits on {alpha} are still below unity, with {alpha} {approx}< 0.95 and {alpha} {approx}< 0.84 for Models B and C, respectively. Our analysis suggests that the satellite AGN occupation increases slower than, or may even decrease with, M{sub h}, in contrast to the satellite HODs of luminosity-threshold samples of galaxies, which, in contrast, grow approximately as (N{sub s}) {proportional_to} M{sup {alpha}}{sub h} with {alpha} {approx} 1. These results are consistent with observations that the AGN fraction in groups and clusters

  20. Type-II AGN population from the zCOSMOS survey

    NASA Astrophysics Data System (ADS)

    Bongiorno, A.; Mignoli, M.; Zamorani, G.; Zcosmos Team

    2008-10-01

    I'll present the first results on the type-II AGN population isolated from the zCOSMOS bright sample which consists of 10k sources, purely magnitude selected at I=22.5. The selected type-II AGN sample consists of about 200 AGN, selected using the diagnostic diagrams up to redshift ~1.0. I'll present the properties of this sample (i.e. SED and morphology) and some preliminary results on the evolution of type-II AGN, as well as on the evolution of their fraction with respect to the total AGN population (Type-I + Type-II), as a function of both luminosity and redshift.

  1. Incidence of WISE -selected obscured AGNs in major mergers and interactions from the SDSS

    NASA Astrophysics Data System (ADS)

    Weston, Madalyn E.; McIntosh, Daniel H.; Brodwin, Mark; Mann, Justin; Cooper, Andrew; McConnell, Adam; Nielsen, Jennifer L.

    2017-02-01

    We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z ≤ 0.08) catalogue of visually selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2 × 1010 M⊙, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4] - [4.6] colours associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fibre spectral diagnostics, we map the [3.4] - [4.6] versus [4.6] - [12] colours of different emission-line galaxies and find that one-quarter of Seyferts have colours indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star forming and located at the centres of Mhalo < 1013 M⊙ groups. Assuming plausibly short-duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations.

  2. AGN contamination in total infrared determined star formation rates in dusty galaxies at z~2-3

    NASA Astrophysics Data System (ADS)

    Mazzei, Renato; Sharon, Chelsea E.; Riechers, Dominik

    2017-01-01

    Along with theoretical work that suggests feedback from active galactic nuclei (AGN) may quench star formation in massive galaxies, the temporal coincidence between the peak of cosmic star formation rates and black hole accretion rates suggests that AGN are common in star forming galaxies at z~2-3. Since star forming galaxies at these epochs are also very dusty, it is important that we correct galaxies’ long-wavelength properties for the presence of dust-obscured AGN in order to accurately capture their star formation rates and gas characteristics. We present a spectral energy distribution (SED) analysis of several un-lensed z~2-3 dusty star-forming galaxies from Pope et al. (2008) and Coppin et al. (2010), which we compare to several other high-z starbursts with well sampled SEDs. We constructed dust SEDs from existing Spitzer, Herschel, and SCUBA-2 photometry catalogues with data between 3.6 and 850 μm. For the SED fits, we used the Code Investigating GALaxy Emission (CIGALE), since it self-consistently determines the dust attenuation of stars and dust emission in the infrared in addition to determining the dust emission from obscured AGN (Noll et al. 2009; Serra et al. 2011). Our best-fit SEDs have typical reduced χ2 values between 0.2 and ~3. We use the output from CIGALE to determine the fraction of the total infrared luminosity (LTIR 8-1000 um) from star formation and from any potential obscured AGN. In order to examine the effects of buried AGN on the integrated Schmidt-Kennicutt relation (log(LTIR) vs. log(L'CO)), we compare our new LTIR to recently obtained CO(1-0) line luminosities from the Karl G. Jansky Very Large Array. Unaccounted for dust emission from AGN can artificially inflate the star formation rate inferred from LTIR, and may therefore offset starburst galaxies from the local Schmidt-Kennicutt relation and increase the slope of the relation, which can affect the inferred drivers of star formation.

  3. An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.; Song, Mimi; Behroozi, Peter; Somerville, Rachel S.; Papovich, Casey; Milosavljević, Miloš; Dekel, Avishai; Narayanan, Desika; Ashby, Matthew L. N.; Cooray, Asantha; Fazio, Giovanni G.; Ferguson, Henry C.; Koekemoer, Anton M.; Salmon, Brett; Willner, S. P.

    2015-12-01

    Recent observations have shown that the characteristic luminosity of the rest-frame ultraviolet (UV) luminosity function does not significantly evolve at 4 < z < 7 and is approximately {M}{UV}*˜ -21. We investigate this apparent non-evolution by examining a sample of 173 bright, MUV < -21 galaxies at z = 4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that {M}{UV}* galaxies at z = 4-7 have similar stellar masses of log(M/M⊙) = 9.6-9.9 and are thus relatively massive for these high redshifts. However, bright galaxies at z = 4-7 are less massive and have younger inferred ages than similarly bright galaxies at z = 2-3, even though the two populations have similar star formation rates and levels of dust attenuation for a fixed dust-attenuation curve. Matching the abundances of these bright z = 4-7 galaxies to halo mass functions from the Bolshoi ΛCDM simulation implies that the typical halo masses in ˜ {M}{{UV}}* galaxies decrease from log(Mh/M⊙) = 11.9 at z = 4 to log(Mh/M⊙) = 11.4 at z = 7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in ˜ {M}{{UV}}* galaxies in units of the cosmic mean Ωb/Ωm rises from 5.1% at z = 4 to 11.7% at z = 7; this evolution is significant at the ˜3σ level. This rise does not agree with simple expectations of how galaxies grow, and implies that some effect, perhaps a diminishing efficiency of feedback, is allowing a higher fraction of available baryons to be converted into stars at high redshifts.

  4. On the relation between X-ray absorption and optical extinction in AGN

    NASA Astrophysics Data System (ADS)

    Ordovás-Pascual, I.; Mateos, S.; Carrera, F. J.; Wiersema, K.; Caccianiga, A.; Della Ceca, R.; Severgnini, P.; Moretti, A.; Ballo, L.

    2017-03-01

    According to the Unified Model of Active Galactic Nuclei (AGN), an X-ray unabsorbed AGN should appear as unobscured in the optical band (the so called type-1 AGN). However, there is an important fraction (10–30%) of AGN whose optical and X-ray classifications do not match. To provide insight into the origin of such apparent discrepancies, we have conducted two types of analysis: 1) a detailed study of the UV-to-near-IR emission of two X-ray low absorbed AGN with high optical extinction drawn from the Bright Ultra-Hard XMM-Newton Survey (BUXS); 2) a statistical analysis of the optical obscuration and X-ray absorption properties of 159 type-1 AGN drawn from BUXS to determine the distribution of dust-to-gas ratios in AGN over a broad range of luminosities and redshifts. We have determined the impact of contamination from the AGN hosts in their optical classification (detection or lack of detection of rest-frame UV-optical broad emission lines). This is an on-going project, but our preliminary results, reported below, are very promising.

  5. The Emission Line AGN Census: Biases of Line Ratio Selection, and Uniform Black Hole Accretion Regardless of Galaxy Mass

    NASA Astrophysics Data System (ADS)

    Trump, Jonathan R.; Zeimann, Gregory; Juneau, Stephanie; Sun, Mouyuan; Luck, Cuyler

    2015-01-01

    Optical emission line ratios offer a powerful tool to reveal accretion onto supermassive black holes, with the ability to find both unobscured and obscured active galactic nuclei (AGNs) in extraordinarily large galaxy samples (like the SDSS). I will demonstrate, however, that classic line ratio selection techniques significantly underestimate the AGN fraction by a factor of >10 in low-mass and star-forming galaxies. Previous conclusions that AGNs require massive green-valley hosts are purely a result of this "star formation dilution" bias. Careful treatment of the biases reveals that AGN accretion is uniform across star-forming galaxies of any stellar mass, similar to the results of bias-corrected X-ray AGN studies. This has dramatic implications for AGN feedback in dwarf galaxies and constraints on the black hole seed population.

  6. Accretion Timescales from Kepler AGN

    NASA Astrophysics Data System (ADS)

    Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.

    2015-01-01

    We constrain AGN accretion disk variability mechanisms using the optical light curves of AGN observed by Kepler. AGN optical fluxes are known to exhibit stochastic variations on timescales of hours, days, months and years. The excellent sampling properties of the original Kepler mission - high S/N ratio (105), short sampling interval (30 minutes), and long sampling duration (~ 3.5 years) - allow for a detailed examination of the differences between the variability processes present in various sub-types of AGN such as Type I and II Seyferts, QSOs, and Blazars. We model the flux data using the Auto-Regressive Moving Average (ARMA) representation from the field of time series analysis. We use the Kalman filter to determine optimal mode parameters and use the Akaike Information Criteria (AIC) to select the optimal model. We find that optical light curves from Kepler AGN cannot be fit by low order statistical models such as the popular AR(1) process or damped random walk. Kepler light curves exhibit complicated power spectra and are better modeled by higher order ARMA processes. We find that Kepler AGN typically exhibit power spectra that change from a bending power law (PSD ~ 1/fa) to a flat power spectrum on timescales in the range of ~ 5 - 100 days consistent with the orbital and thermal timescales of a typical 107 solar mass black hole.

  7. Probing AGN Accretion Physics through AGN Variability: Insights from Kepler

    NASA Astrophysics Data System (ADS)

    Kasliwal, Vishal Pramod

    Active Galactic Nuclei (AGN) exhibit large luminosity variations over the entire electromagnetic spectrum on timescales ranging from hours to years. The variations in luminosity are devoid of any periodic character and appear stochastic. While complex correlations exist between the variability observed in different parts of the electromagnetic spectrum, no frequency band appears to be completely dominant, suggesting that the physical processes producing the variability are exceedingly rich and complex. In the absence of a clear theoretical explanation of the variability, phenomenological models are used to study AGN variability. The stochastic behavior of AGN variability makes formulating such models difficult and connecting them to the underlying physics exceedingly hard. We study AGN light curves serendipitously observed by the NASA Kepler planet-finding mission. Compared to previous ground-based observations, Kepler offers higher precision and a smaller sampling interval resulting in potentially higher quality light curves. Using structure functions, we demonstrate that (1) the simplest statistical model of AGN variability, the damped random walk (DRW), is insufficient to characterize the observed behavior of AGN light curves; and (2) variability begins to occur in AGN on time-scales as short as hours. Of the 20 light curves studied by us, only 3-8 may be consistent with the DRW. The structure functions of the AGN in our sample exhibit complex behavior with pronounced dips on time-scales of 10-100 d suggesting that AGN variability can be very complex and merits further analysis. We examine the accuracy of the Kepler pipeline-generated light curves and find that the publicly available light curves may require re-processing to reduce contamination from field sources. We show that while the re-processing changes the exact PSD power law slopes inferred by us, it is unlikely to change the conclusion of our structure function study-Kepler AGN light curves indicate

  8. EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

    SciTech Connect

    Suh, Hyewon; Hasinger, Günther; Steinhardt, Charles; Silverman, John D.; Schramm, Malte

    2015-12-20

    We investigate the Eddington ratio distribution of X-ray-selected broad-line active galactic nuclei (AGNs) in the redshift range 1.0 < z < 2.2, where the number density of AGNs peaks. Combining the optical and Subaru/Fiber Multi Object Spectrograph near-infrared spectroscopy, we estimate black hole masses for broad-line AGNs in the Chandra Deep Field South (CDF-S), Extended Chandra Deep Field South (E-CDF-S), and the XMM-Newton Lockman Hole (XMM-LH) surveys. AGNs with similar black hole masses show a broad range of AGN bolometric luminosities, which are calculated from X-ray luminosities, indicating that the accretion rate of black holes is widely distributed. We find a substantial fraction of massive black holes accreting significantly below the Eddington limit at z ≲ 2, in contrast to what is generally found for luminous AGNs at high redshift. Our analysis of observational selection biases indicates that the “AGN cosmic downsizing” phenomenon can be simply explained by the strong evolution of the comoving number density at the bright end of the AGN luminosity function, together with the corresponding selection effects. However, one might need to consider a correlation between the AGN luminosity and the accretion rate of black holes, in which luminous AGNs have higher Eddington ratios than low-luminosity AGNs, in order to understand the relatively small fraction of low-luminosity AGNs with high accretion rates in this epoch. Therefore, the observed downsizing trend could be interpreted as massive black holes with low accretion rates, which are relatively fainter than less-massive black holes with efficient accretion.

  9. The 60 Month All-Sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of Nearby AGNs

    NASA Technical Reports Server (NTRS)

    Ajello, M.; Alexander, D. M.; Greiner, J.; Madejeski, G. M.; Gehrels, N.; Burlon, D.

    2014-01-01

    Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of approx. 2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent approx. 5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to approx. 10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9(+4.1/-2.9)× 10(exp -5)/cubic Mpc for objects with a de-absorbed luminosity larger than 2 × 10(exp 42) erg / s. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local (much < 85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions..

  10. X-Ray Absorption, Nuclear Infrared Emission, and Dust Covering Factors of AGNs: Testing Unification Schemes

    NASA Astrophysics Data System (ADS)

    Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Hernán-Caballero, A.; Barcons, X.; Asensio Ramos, A.; Watson, M. G.; Blain, A.; Caccianiga, A.; Ballo, L.; Braito, V.; Ramos Almeida, C.

    2016-03-01

    We present the distributions of the geometrical covering factors of the dusty tori (f2) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2-10 keV luminosities between 1042 and 1046 erg s-1, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1-20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f2 than type 1 AGNs. Nevertheless, ˜20% of type 1 AGNs have tori with large covering factors, while ˜23%-28% of type 2 AGNs have tori with small covering factors. Low f2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f2 increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f2 determine the optical appearance of an AGN and control the shape of the rest-frame ˜1-20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.

  11. X-RAY ABSORPTION, NUCLEAR INFRARED EMISSION, AND DUST COVERING FACTORS OF AGNs: TESTING UNIFICATION SCHEMES

    SciTech Connect

    Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Hernán-Caballero, A.; Barcons, X.; Ramos, A. Asensio; Almeida, C. Ramos; Watson, M. G.; Blain, A.; Caccianiga, A.; Ballo, L.; Braito, V.

    2016-03-10

    We present the distributions of the geometrical covering factors of the dusty tori (f{sub 2}) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2–10 keV luminosities between 10{sup 42} and 10{sup 46} erg s{sup −1}, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1–20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f{sub 2} than type 1 AGNs. Nevertheless, ∼20% of type 1 AGNs have tori with large covering factors, while ∼23%–28% of type 2 AGNs have tori with small covering factors. Low f{sub 2} are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f{sub 2} increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f{sub 2} determine the optical appearance of an AGN and control the shape of the rest-frame ∼1–20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.

  12. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with Square Kilometre Array

    NASA Astrophysics Data System (ADS)

    Kharb, P.; Lal, D. V.; Singh, V.; Bagchi, J.; Ishwara Chandra, C. H.; Hota, A.; Konar, C.; Wadadekar, Y.; Shastri, P.; Das, M.; Baliyan, K.; Nath, B. B.; Pandey-Pommier, M.

    2016-12-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

  13. AGN Observations with STACEE

    NASA Astrophysics Data System (ADS)

    Bramel, D. A.; Boone, L. M.; Carson, J.; Chae, E.; Covault, C. E.; Fortin, P.; Gingrich, D. M.; Hanna, D. S.; Hinton, J. A.; Mukherjee, R.; Mueller, C.; Ong, R. A.; Ragan, K.; Scalzo, R. A.; Schuette, D. R.; Theoret, C. G.; Williams, D. A.; Wong, J.; Zweerink, J.

    2003-03-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a gamma-ray detector designed to study astrophysical sources at energies between 50 and 500 GeV. It uses 64 large, steerable mirrors at the National Solar Tower Test Facility near Albuquerque, NM, USA to collect Cherenkov light from extended air showers and concentrate it onto an array of photomultiplier tubes. The large light-collection area gives it a lower energy threshold than imaging-type Cherenkov detectors. STACEE is now fully operational, and we report here on the performance of the complete STACEE instrument, as well as preliminary results of recent observations of several AGN targets. This work was supported in part by the National Science Foundation (under Grant Numbers PHY-9983836, PHY-0070927, and PHY-0070953), the Natural Sciences and Engineering Research Council, Le Fond Quebecois de la Recherche sur la Nature et les Technologies (FQRNT), the Research Corporation, and the California Space Institute. CEC is a Cottrell Scholar of the Research Corporation.

  14. Intermittent Activity in AGN

    NASA Astrophysics Data System (ADS)

    Janiuk, A.; Czerny, B.; Siemiginowska, A.

    2004-10-01

    There is a growing evidence that the AGN activity could be intermittent. It remains an open question if this behavior is caused by changes in the fuel sup- ply to the supermassive black hole from the large distances, or rather by a processes intrinsic to the active nucleus. We consider the possibility that ac- cretion onto a supermassive black hole is controlled by an accretion disk which is subject to the hydro- gen ionization instability. This drives the observed on-off activity cycle, since periodically the accretion flow becomes inefficient and the disk goes to quies- cence. We consider effects of the MHD turbulence on the viscosity during the evolution of a standard α - disk. We perform a self-consistency check of the α de- scription of the angular momentum transfer. Hav- ing shown that the viscosity parameter is constant throughout the whole instability cycle, as implied by the strength of the MHD turbulence, we calcu- late the time evolution of the disk under the influ- ence of the ionization instability. We demonstrate that if the accretion onto a supermassive black hole proceeds through an outer standard accretion disk and inner, radiatively inefficient and advection dom- inated flow, the modelled amplitudes of disk lumi- nosity variations are sufficiently high to account for the observations. Key words: accretion disks; galaxies: active.

  15. Increasing the accuracy and automation of fractional vegetation cover estimation from digital photographs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of automated methods to estimate canopy cover (CC) from digital photographs has increased in recent years given its potential to produce accurate, fast and inexpensive CC measurements. Wide acceptance has been delayed because of the limitations of these methods. This work introduces a novel ...

  16. AGN host galaxy mass function in COSMOS. Is AGN feedback responsible for the mass-quenching of galaxies?

    NASA Astrophysics Data System (ADS)

    Bongiorno, A.; Schulze, A.; Merloni, A.; Zamorani, G.; Ilbert, O.; La Franca, F.; Peng, Y.; Piconcelli, E.; Mainieri, V.; Silverman, J. D.; Brusa, M.; Fiore, F.; Salvato, M.; Scoville, N.

    2016-04-01

    We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λSAR, the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λSAR slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λSAR objects have a peak in their space density at earlier epoch than the lower λSAR objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M∗⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M⋆/M⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M⋆ > 1010.7 M⊙, feedback from luminous AGN (log Lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

  17. Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity

    NASA Astrophysics Data System (ADS)

    Davies, Rebecca L.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Hampton, Elise J.; Shastri, Prajval; Scharwächter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-10-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and active galactic nucleus (AGN) activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion on to an AGN. We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (>85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated spectrum. We separate the Hα, Hβ, [N II]λ6583, [S II]λλ6716, 6731, [O III]λ5007 and [O II]λλ3726, 3729 luminosities of every spaxel into contributions from star formation and AGN activity. The decomposed emission line images are used to derive the star formation rates and AGN bolometric luminosities for NGC 5728 and NGC 7679. Our calculated values are mostly consistent with independent estimates from data at other wavelengths. The recovered star-forming and AGN components also have distinct spatial distributions which trace structures seen in high-resolution imaging of the galaxies, providing independent confirmation that our decomposition has been successful.

  18. AGN jets as pion factories

    NASA Astrophysics Data System (ADS)

    Mannheim, Karl

    There has been a dramatic revolution in gamma-ray astronomy throughout the last few years. Beginning with the discovery made by the spark chamber EGRET on board the Compton Gamma Ray Observatory that AGN with jets are the most powerful quasi-steady gamma-ray sources in the Universe, air-Cerenkov telescopes have soon after succeeded in detecting gamma-rays up to TeV energies. In the last year, it has become clear that these AGN emit photons even up to 10 TeV and more. This is a strong indication for proton acceleration going on in them, since protons owing to their large mass suffer weaker energy losses than electrons and can thus reach higher energies. Nucleons escaping from the AGN jets contribute to the local flux of cosmic rays at highest energies. If AGN produce the diffuse gamma-ray background, they would also be able to produce all the cosmic rays above the ankle in the local spectrum. The majority of AGN resides at large distances, indicated by their cosmological redshifts, and can therefore not be seen through the fog of electron-positron pairs which they produce interacting with diffuse infrared radiation from the era of galaxy formation. To observe the cosmic accelerators at large redshifts, neutrino observations are required. It is important to understand the astrophysical neutrino sources in order to be able to recognize signatures of new physics, e.g. due to decaying or annihilating particles from the early phases of the Universe.

  19. Memory-enhancing corticosterone treatment increases amygdala norepinephrine and Arc protein expression in hippocampal synaptic fractions.

    PubMed

    McReynolds, Jayme R; Donowho, Kyle; Abdi, Amin; McGaugh, James L; Roozendaal, Benno; McIntyre, Christa K

    2010-03-01

    Considerable evidence indicates that glucocorticoid hormones enhance the consolidation of memory for emotionally arousing events through interactions with the noradrenergic system of the basolateral complex of the amygdala (BLA). We previously reported that intra-BLA administration of a beta-adrenoceptor agonist immediately after inhibitory avoidance training enhanced memory consolidation and increased hippocampal expression of the protein product of the immediate early gene activity-regulated cytoskeletal-associated protein (Arc). In the present experiments corticosterone (3 mg/kg, i.p.) was administered to male Sprague-Dawley rats immediately after inhibitory avoidance training to examine effects on long-term memory, amygdala norepinephrine levels, and hippocampal Arc expression. Corticosterone increased amygdala norepinephrine levels 15 min after inhibitory avoidance training, as assessed by in vivo microdialysis, and enhanced memory tested at 48 h. Corticosterone treatment also increased expression of Arc protein in hippocampal synaptic tissue. The elevation in BLA norepinephrine appears to participate in corticosterone-influenced modulation of hippocampal Arc expression as intra-BLA blockade of beta-adrenoceptors with propranolol (0.5 microg/0.2 microL) attenuated the corticosterone-induced synaptic Arc expression in the hippocampus. These findings indicate that noradrenergic activity at BLA beta-adrenoceptors is involved in corticosterone-induced enhancement of memory consolidation and expression of the synaptic-plasticity-related protein Arc in the hippocampus.

  20. Heavily Obscured AGN with SIMBOL-X

    SciTech Connect

    Ceca, R. Della; Caccianiga, A.; Severgnini, P.

    2009-05-11

    By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s)

  1. Heavily Obscured AGN with SIMBOL-X

    NASA Astrophysics Data System (ADS)

    Della Ceca, R.; Caccianiga, A.; Severgnini, P.

    2009-05-01

    By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s).

  2. AGN identification: what lies ahead

    NASA Astrophysics Data System (ADS)

    Fotopoulou, Sotiria

    2016-08-01

    Classification has been one the first concerns of modern astronomy, starting from stars sorted in the famous Harvard classification system and promptly followed by the morphological classification of galaxies by none other than Edwin Hubble himself (Hubble 1926). Both classification schema are essentially connected to the physics of the objects reflecting the temperature for stars and e.g. the age of the star population for galaxies. Systematic observations of galaxies have revealed the intriguing class of Active Galactic Nuclei (AGN), objects of tremendous radiation that do not share the same properties of what we now call normal galaxies. Observations have led to the definition of distinct and somewhat arbitrary categories (Seyfert galaxies, quasars, QSO, radio AGN, etc), essentially rediscovering the many faces of the same phenomenon, up until the unification of AGN (Antonucci 1993, Urry and Padovani 1995). Even after the realization that all AGN have the same engine powering their amazing radiation, astronomers are still using and refining the selection criteria within their favorite electromagnetic range in the hope to better understand the impact of the AGN phenomenon in the greater context of galaxy evolution. In the dawn of Big Data astronomy we find ourselves equipped with new tools. I will present the prospects of machine learning methods in better understanding the AGN population. Namely, I will show results from supervised learning algorithms whereby a labeled training set is used to amalgamate decision tree(s) (Fotopoulou et al., 2016) or neural network(s), and unsupervised learning where the algorithm performs clustering analysis of the full dataset in a multidimensional space identifying clusters of objects sharing potentially the same physical properties (Fotopoulou in prep.).

  3. Accretion-ejection models for AGN jets

    NASA Astrophysics Data System (ADS)

    Zanni, C.

    2008-10-01

    It is likely that jets from Active Galactic Nuclei derive their energy from accretion onto the central black hole. It is actually possible to fuel the jets by extracting energy and angular momentum from the accretion disk and/or the rotating black hole via the action of large-scale magnetic fields. In this talk I will first present results of analytical and numerical models of the launching process of jets from magnetized accretion disks: I will show that, although a sizeable fraction of the accretion power goes into the jets, these outflows are presumably only mildly relativistic. In the second place, I will therefore suggest that the strongly relativistic components observed at the VLBI scales are accelerated in the innermost parts of the AGNs by Blandford-Znajek and/or Compton-rocket processes. Nonetheless, the non-relativistic disk-wind is needed to collimate the relativistic component and to reproduce the total power of extragalactic jets.

  4. VizieR Online Data Catalog: Optically bright AGN in ROSAT-FSC (Veron-Cetty+, 2004)

    NASA Astrophysics Data System (ADS)

    Veron-Cetty, M.-P.; Balayan, S. K.; Mickaelian, A. M.; Mujica, R.; Chavushyan, V.; Hakopian, S. A.; Engels, D.; Veron, P.; Zickgraf, F.-J.; Voges, W.; Xu, D.-W.

    2004-02-01

    To build a large, optically bright, X-ray selected AGN sample we have correlated the ROSAT-FSC () catalogue of X-ray sources with the USNO () catalogue limited to objects brighter than O=16.5 and then with the APS () database. Each of the 3212 coincidences was classified using the slitless Hamburg spectra. 493 objects were found to be extended and 2719 starlike. Using both the extended objects and the galaxies known from published catalogues we built up a sample of 185 galaxies with O(APS)<17.0mag, which are high-probability counterparts of RASS-FSC X-ray sources. 130 galaxies have a redshift from the literature and for another 34 we obtained new spectra. The fraction of Seyfert galaxies in this sample is 20%. To select a corresponding sample of 144 high-probability counterparts among the starlike sources we searched for very blue objects in an APS-based color-magnitude diagram. Forty-one were already known AGN and for another 91 objects we obtained new spectra, yielding 42 new AGN, increasing their number in the sample to 83. This confirms that surveys of bright QSOs are still significantly incomplete. On the other hand we find that, at a flux limit of 0.02ct/s and at this magnitude, only 40% of all QSOs are detected by ROSAT. (3 data files).

  5. Fading AGN Candidates: AGN Histories and Outflow Signatures

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Lintott, Chris J.; Maksym, W. Peter; Bennert, Vardha N.; Chojnowski, S. Drew; Moiseev, Alexei; Smirnova, Aleksandrina; Schawinski, Kevin; Sartori, Lia F.; Urry, C. Megan; Pancoast, Anna; Schirmer, Mischa; Scott, Bryan; Showley, Charles; Flatland, Kelsi

    2017-02-01

    We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Qion derived from photoionization balance in the brightest pixels in Hα at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Qion values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2 × 104 yr before the direct view of the nucleus. The e-folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission

  6. Centella asiatica accelerates nerve regeneration upon oral administration and contains multiple active fractions increasing neurite elongation in-vitro.

    PubMed

    Soumyanath, Amala; Zhong, Yong-Ping; Gold, Sandra A; Yu, Xiaolin; Koop, Dennis R; Bourdette, Dennis; Gold, Bruce G

    2005-09-01

    Axonal regeneration is important for functional recovery following nerve damage. Centella asiatica Urban herb, also known as Hydrocotyle asiatica L., has been used in Ayurvedic medicine for centuries as a nerve tonic. Here, we show that Centella asiatica ethanolic extract (100 microg mL-1) elicits a marked increase in neurite outgrowth in human SH-SY5Y cells in the presence of nerve growth factor (NGF). However, a water extract of Centella was ineffective at 100 microg mL-1. Sub-fractions of Centella ethanolic extract, obtained through silica-gel chromatography, were tested (100 microg mL-1) for neurite elongation in the presence of NGF. Greatest activity was found with a non-polar fraction (GKF4). Relatively polar fractions (GKF10 to GKF13) also showed activity, albeit less than GKF4. Thus, Centella contains more than one active component. Asiatic acid (AA), a triterpenoid compound found in Centella ethanolic extract and GKF4, showed marked activity at 1 microM (microg mL-1). AA was not present in GKF10 to GKF13, further indicating that other active components must be present. Neurite elongation by AA was completely blocked by the extracellular-signal-regulated kinase (ERK) pathway inhibitor PD 098059 (10 microM). Male Sprague-Dawley rats given Centella ethanolic extract in their drinking water (300-330 mg kg-1 daily) demonstrated more rapid functional recovery and increased axonal regeneration (larger calibre axons and greater numbers of myelinated axons) compared with controls, indicating that the axons grew at a faster rate. Taken together, our findings indicate that components in Centella ethanolic extract may be useful for accelerating repair of damaged neurons.

  7. The AGN Population and the Cosmic X-ray Background

    NASA Astrophysics Data System (ADS)

    Treister, Ezequiel; Urry, C. Meg; Schawinski, Kevin

    2015-08-01

    In order to fully understand galaxy formation we need to know when in the cosmic history are supermassive black holes (SMBHs) growing more intensively, in what type of galaxies this growth is happening and what fraction of these sources are invisible at most wavelengths due to obscuration. Active Galactic Nuclei (AGN) population synthesis models that can explain the spectral shape and intensity of the cosmic X-ray background (CXRB) indicate that most of the SMBH growth occurs in moderate-luminosity (Lx~1044 erg/s) sources (Seyfert-type AGN), at z~0.5-1 and in heavily obscured but Compton-thin, NH~1023 cm-2, systems.However, this is not the complete history, as a large fraction of black hole growth does not emit significantly in X-rays either due to obscuration, intrinsic low luminosities or large distances. Using a combination of X-ray stacking and multi wavelength selection techniques we constrain the amount of black hole accretion as a function of cosmic history, from z~0 to z~6. The integrated intensity at high energies indicates that a significant fraction of the total black hole growth, 22%, occurs in heavily-obscured systems that are not individually detected in even the deepest X-ray observations.We finally investigate the AGN triggering mechanism as a function of bolometric luminosity, finding evidence for a strong connection between significant black hole growth events and major galaxy mergers from z~0 to z~3, while less spectacular but longer accretion episodes are most likely due to other (stochastic) processes. AGN activity triggered by major galaxies is responsible for ~60% of the total black hole growth.

  8. The Close AGN Reference Survey (CARS)

    NASA Astrophysics Data System (ADS)

    Rothberg, Barry; Husemann, Bernd; Busch, Gerold; Dierkes, Jens; Eckart, Andreas; Krajnovic, Davor; Scharwaechter, Julia; Tremblay, Grant R.; Urrutia, Tanya

    2015-08-01

    We present the first science results from the Close AGN Reference Survey (CARS). This program is a snapshot survey of 39 local type 1 AGN (0.01 < z <0.06) designed to address the issue of AGN-driven star formation quenching by characterizing the condition for star formation in AGN host galaxies. The primary sample was observed with Multi Unit Spectrscopic Explorer (MUSE), an optical wavelength integral field unit (IFU) with a 1'x1' field of view on the VLT. The optical 3D spectroscopy complements existing sub-mm CO(1-0) data and near-IR imaging to establish a unique dataset combining molecular and stellar masses with star formation rates, gas, stellar kinematics and AGN properties. The primary goals of CARS are to:1) investigate if the star formation efficiency and gas depletion time scales are suppressed as a consequence of AGN feedback; 2) identify AGN-driven outflows and their relation to the molecular gas reservoir of the host galaxy; 3) investigate the the balance of AGN feeding and feedback through the ratio of the gas reservoir to the AGN luminosity; and 4) provide the community with a reference survey of local AGN with a high legacy value. Future work will incorporate near-infrared IFU observations to present a complete spatially resolved picture of the interplay among AGN, star-formation, stellar populations, and the ISM.

  9. Increased left ventricular ejection fraction after a meal: potential source of error in performance of radionuclide angiography

    SciTech Connect

    Brown, J.M.; White, C.J.; Sobol, S.M.; Lull, R.J.

    1983-06-01

    The effect of a standardized meal on left ventricular (LV) ejection fraction (EF) was determined by equilibrium radionuclide angiography in 16 patients with stable congestive heart failure but without pulmonary or valvular heart disease. LVEF was determined in the fasting state and 15, 30, and 45 minutes after a meal. Patients with moderately depressed fasting LVEF (30 to 50%), Group I, had a mean increase of 6.9 +/- 2.9% (p less than 0.005) in the LVEF at 45 minutes after the meal. Patients with severely depressed fasting LVEF (less than 30%), Group II, had no change after the meal. It is concluded that significant increases in LVEF may occur after meals in patients with moderate but not severe left ventricular dysfunction. Equilibrium radionuclide angiography studies that are not standardized for patients' mealtimes may introduce an important unmeasured variable that will affect the validity of data in serial studies of left ventricular function.

  10. X-ray selected AGN in groups at redshifts z ~ 1

    NASA Astrophysics Data System (ADS)

    Georgakakis, A.; Gerke, Brian F.; Nandra, K.; Laird, E. S.; Coil, A. L.; Cooper, M. C.; Newman, J. A.

    2008-11-01

    We explore the role of the group environment in the evolution of active galactic nuclei (AGN) at the redshift interval 0.7 < z < 1.4, by combining deep Chandra observations with extensive optical spectroscopy from the All-wavelength Extended Groth strip International Survey (AEGIS). The sample consists of 3902 optical sources and 71 X-ray AGN. Compared to the overall optically selected galaxy population, X-ray AGN are more frequently found in groups at the 99 per cent confidence level. This is partly because AGN are hosted by red luminous galaxies, which are known to reside, on average, in dense environments. Relative to these sources, the excess of X-ray AGN in groups is significant at the 91 per cent level only. Restricting the sample to 0.7 < z < 0.9 and MB < -20mag in order to control systematics, we find that X-ray AGN represent (4.7 +/- 1.6) and (4.5 +/- 1.0) per cent of the optical galaxy population in groups and in the field, respectively. These numbers are consistent with the AGN fraction in low-redshift clusters, groups and the field. The above results, although affected by small number statistics, suggest that X-ray AGN are spread over a range of environments, from groups to the field, once the properties of their hosts (e.g. colour, luminosity) are accounted for. There is also tentative evidence, significant at the 98 per cent level, that the field produces more X-ray luminous AGN compared to groups, extending similar results at low redshift to z ~ 1. This trend may be because of either cold gas availability or the nature of the interactions occurring in the denser group environment (i.e. prolonged tidal encounters).

  11. On the Importance of Very Light Internally Subsonic AGN Jets in Radio-mode AGN Feedback

    NASA Astrophysics Data System (ADS)

    Guo, Fulai

    2016-07-01

    Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light (η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonic jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.

  12. Searching for Dual AGNs in Galaxy Mergers: Understanding Double-Peaked [O III] and Ultra Hard X-rays as Selection Method

    NASA Astrophysics Data System (ADS)

    McGurk, Rosalie C.; Max, Claire E.; Medling, Anne; Shields, Gregory A.

    2015-01-01

    When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see close pairs of active galactic nuclei (AGNs), or dual AGNs, in a fraction of galaxy mergers. However, finding them remains a challenge. The presence of double-peaked [O III] or of ultra hard X-rays have been proposed as techniques to select dual AGNs efficiently. We studied a sample of double-peaked narrow [O III] emitting AGNs from SDSS DR7. By obtaining new and archival high spatial resolution images taken with the Keck 2 Laser Guide Star Adaptive Optics system and the near-infrared (IR) camera NIRC2, we showed that 30% of double-peaked [O III] emission line SDSS AGNs have two spatial components within a 3' radius. However, spatially resolved spectroscopy or X-ray observations are needed to confirm these galaxy pairs as systems containing two AGNs. We followed up these spatially-double candidate dual AGNs with integral field spectroscopy from Keck OSIRIS and Gemini GMOS and with long-slit spectroscopy from Keck NIRSPEC and Shane Kast Double Spectrograph. We find double-peaked emitters are caused sometimes by dual AGN and sometimes by outflows or narrow line kinematics. We also performed Chandra X-ray ACIS-S observations on 12 double-peaked candidate dual AGNs. Using our observations and 8 archival observations, we compare the distribution of X-ray photons to our spatially double near-IR images, measure X-ray luminosities and hardness ratios, and estimate column densities. By assessing what fraction of double-peaked emission line SDSS AGNs are true dual AGNs, we can better determine whether double-peaked [O III] is an efficient dual AGN indicator and constrain the statistics of dual AGNs. A second technique to find dual AGN is the detection of ultra hard X-rays by the Swift Burst Alert Telescope. We use CARMA observations to measure and map the CO(1-0) present in nearby ultra-hard X-ray Active Galactic Nuclei (AGNs) merging with either a quiescent companion

  13. A SOFT X-RAY REVERBERATION LAG IN THE AGN ESO 113-G010

    SciTech Connect

    Cackett, E. M.; Fabian, A. C.; Kara, E.; Zogbhi, A.; Reynolds, C.; Uttley, P.

    2013-02-10

    Reverberation lags have recently been discovered in a handful of nearby, variable active galactic nuclei (AGNs). Here, we analyze a {approx}100 ks archival XMM-Newton observation of the highly variable AGN, ESO 113-G010, in order to search for lags between hard, 1.5-4.5 keV, and soft, 0.3-0.9 keV, energy X-ray bands. At the lowest frequencies available in the light curve ({approx}< 1.5 Multiplication-Sign 10{sup -4} Hz), we find hard lags where the power-law-dominated hard band lags the soft band (where the reflection fraction is high). However, at higher frequencies in the range (2-3) Multiplication-Sign 10{sup -4} Hz we find a soft lag of -325 {+-} 89 s. The general evolution from hard to soft lags as the frequency increases is similar to other AGNs where soft lags have been detected. We interpret this soft lag as due to reverberation from the accretion disk, with the reflection component responding to variability from the X-ray corona. For a black hole mass of 7 Multiplication-Sign 10{sup 6} M{sub Sun} this corresponds to a light-crossing time of {approx}9 R{sub g} /c; however, dilution effects mean that the intrinsic lag is likely longer than this. Based on recent black hole mass scaling for lag properties, the lag amplitude and frequency are more consistent with a black hole a few times more massive than the best estimates, though flux-dependent effects could easily add scatter this large.

  14. Modification of aqueous enzymatic oil extraction to increase the yield of corn oil from dry fractionated corn germ

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In previous aqueous enzymatic extraction experiments we reported an oil yield of 67 grams from 800 grams of dry fractionated corn germ. In the current experiments, a dispersion of 10% cooked, dry-fractionated germ in water and was treated with amylases and a cellulase complex. A foam fraction was s...

  15. More is not always better: increased fractional anisotropy of superior longitudinal fasciculus associated with poor visuospatial abilities in Williams syndrome.

    PubMed

    Hoeft, Fumiko; Barnea-Goraly, Naama; Haas, Brian W; Golarai, Golijeh; Ng, Derek; Mills, Debra; Korenberg, Julie; Bellugi, Ursula; Galaburda, Albert; Reiss, Allan L

    2007-10-31

    We used diffusion tensor imaging to examine white matter integrity in the dorsal and ventral streams among individuals with Williams syndrome (WS) compared with two control groups (typically developing and developmentally delayed) and using three separate analysis methods (whole brain, region of interest, and fiber tractography). All analysis methods consistently showed that fractional anisotropy (FA; a measure of microstructural integrity) was higher in the right superior longitudinal fasciculus (SLF) in WS compared with both control groups. There was a significant association with deficits in visuospatial construction and higher FA in WS individuals. Comparable increases in FA across analytic methods were not observed in the left SLF or the bilateral inferior longitudinal fasciculus in WS subjects. Together, these findings suggest a specific role of right SLF abnormality in visuospatial construction deficits in WS.

  16. Microbial respiration, but not biomass, responded linearly to increasing light fraction organic matter input: Consequences for carbon sequestration

    PubMed Central

    Rui, Yichao; Murphy, Daniel V.; Wang, Xiaoli; Hoyle, Frances C.

    2016-01-01

    Rebuilding ‘lost’ soil carbon (C) is a priority in mitigating climate change and underpinning key soil functions that support ecosystem services. Microorganisms determine if fresh C input is converted into stable soil organic matter (SOM) or lost as CO2. Here we quantified if microbial biomass and respiration responded positively to addition of light fraction organic matter (LFOM, representing recent inputs of plant residue) in an infertile semi-arid agricultural soil. Field trial soil with different historical plant residue inputs [soil C content: control (tilled) = 9.6 t C ha−1 versus tilled + plant residue treatment (tilled + OM) = 18.0 t C ha−1] were incubated in the laboratory with a gradient of LFOM equivalent to 0 to 3.8 t C ha−1 (0 to 500% LFOM). Microbial biomass C significantly declined under increased rates of LFOM addition while microbial respiration increased linearly, leading to a decrease in the microbial C use efficiency. We hypothesise this was due to insufficient nutrients to form new microbial biomass as LFOM input increased the ratio of C to nitrogen, phosphorus and sulphur of soil. Increased CO2 efflux but constrained microbial growth in response to LFOM input demonstrated the difficulty for C storage in this environment. PMID:27752083

  17. Microbial respiration, but not biomass, responded linearly to increasing light fraction organic matter input: Consequences for carbon sequestration

    NASA Astrophysics Data System (ADS)

    Rui, Yichao; Murphy, Daniel V.; Wang, Xiaoli; Hoyle, Frances C.

    2016-10-01

    Rebuilding ‘lost’ soil carbon (C) is a priority in mitigating climate change and underpinning key soil functions that support ecosystem services. Microorganisms determine if fresh C input is converted into stable soil organic matter (SOM) or lost as CO2. Here we quantified if microbial biomass and respiration responded positively to addition of light fraction organic matter (LFOM, representing recent inputs of plant residue) in an infertile semi-arid agricultural soil. Field trial soil with different historical plant residue inputs [soil C content: control (tilled) = 9.6 t C ha‑1 versus tilled + plant residue treatment (tilled + OM) = 18.0 t C ha‑1] were incubated in the laboratory with a gradient of LFOM equivalent to 0 to 3.8 t C ha‑1 (0 to 500% LFOM). Microbial biomass C significantly declined under increased rates of LFOM addition while microbial respiration increased linearly, leading to a decrease in the microbial C use efficiency. We hypothesise this was due to insufficient nutrients to form new microbial biomass as LFOM input increased the ratio of C to nitrogen, phosphorus and sulphur of soil. Increased CO2 efflux but constrained microbial growth in response to LFOM input demonstrated the difficulty for C storage in this environment.

  18. Accretion Rate: An Axis Of Agn Unification

    NASA Astrophysics Data System (ADS)

    Trump, Jonathan R.; Impey, C. D.; Kelly, B. C.

    2011-01-01

    We show how accretion rate governs the physical properties of broad-line, narrow-line, and lineless active galactic nuclei (AGNs). We avoid the systematic errors plaguing previous studies of AGN accretion rate by using accurate accretion luminosities from well-sampled multiwavelength SEDs from the Cosmic Evolution Survey (COSMOS), and accurate black hole masses derived from virial scaling relations (for broad-line AGNs) or host-AGN relations (for narrow-line and lineless AGNs). In general, broad emission lines are present only at the highest accretion rates (L/L_Edd>0.01), and these rapidly accreting AGNs are observed as broad-line AGNs or possibly as obscured narrow-line AGNs. Narrow-line and lineless AGNs at lower specific accretion rates (L/L_Edd<0.01) are unobscured and yet lack a broad line region. The disappearance of the broad emission lines is caused by an expanding radiatively inefficient accretion flow (RIAF) at the inner radius of the accretion disk. The presence of the RIAF also drives L/L_Edd<0.01 narrow-line and lineless AGNs to be 10-100 times more radio-luminous than broad-line AGNs, since the unbound nature of the RIAF means it is easier to form a radio outflow. The IR torus signature also tends to become weaker or disappear from L/L_Edd<0.01 AGNs, although there may be additional mid-IR synchrotron emission associated with the RIAF. Together these results suggest that specific accretion rate is an important physical "axis" of AGN unification, described by a simple model.

  19. RXTE observations of AGN

    NASA Technical Reports Server (NTRS)

    Rothschild, R. E.; Heindl, W. A.; Blanco, P. R.; Gruber, D. E.; Marsden, D. C.; Pelling, M. R.; Jahoda, K.; Madejski, G.; Swank, J. H.; Zdziarski, A. A.; Gierlinski, M.; Hink, P. L.

    1997-01-01

    The Rossi X-ray Timing Explorer (RXTE) observed three active galaxies during its in-orbit verification phase: NGC 4151; NGC 4945, and MCG 8-11-11. All three were detected from 2 keV to more than 100 keV by a combination of the proportional counter array (PCA) and the high energy X-ray timing experiment (HEXTE). The PCA contains five, xenon/methane, multilayer, multiwire, gas proportional counters covering the 2 to 60 keV range, while HEXTE is an array of eight NaI/CsI phoswich scintillation counters covering the 15 to 250 keV range. The three active galaxies represent the classes of Seyfert 1, Seyfert 2 and intermediate Seyfert galaxies. The results of the fitting of various models containing partial covering fractions, Compton reflection components and high energy spectral breaks are discussed.

  20. Non-thermal AGN models

    SciTech Connect

    Band, D.L.

    1986-12-01

    The infrared, optical and x-ray continua from radio quiet active galactic nuclei (AGN) are explained by a compact non-thermal source surrounding a thermal ultraviolet emitter, presumably the accretion disk around a supermassive black hole. The ultraviolet source is observed as the ''big blue bump.'' The flat (..cap alpha.. approx. = .7) hard x-ray spectrum results from the scattering of thermal ultraviolet photons by the flat, low energy end of an electron distribution ''broken'' by Compton losses; the infrared through soft x-ray continuum is the synchrotron radiation of the steep, high energy end of the electron distribution. Quantitative fits to specific AGN result in models which satisfy the variability constraints but require electron (re)acceleration throughout the source. 11 refs., 1 fig.

  1. Gamma-ray-selected AGN

    NASA Astrophysics Data System (ADS)

    Giommi, Paolo

    2016-08-01

    The gamma-ray band is the most energetic part of the electromagnetic spectrum. As such it is also where selection effects are most severe, as it can only be reached by the most extreme non-thermal AGN. Blazars, with their emission dominated by non-thermal blue-shifted radiation arising in a relativistic jet pointed in the direction of the observer, naturally satisfy this though requirement. For this reason, albeit these sources are intrisically very rare (orders of magnitude less abundant than radio quiet AGN of the same optical magnitude) they almost completely dominate the extragalactic gamma-ray and very high energy sky. I will discuss the emission of different types of blazars and the selection effects that are at play in the gamma-ray band based on recent results from the current generation of gamma-ray astronomy satellites, ground-based Cherenkov telescopes, and Monte Carlo simulations.

  2. The Importance of Winds for AGN Feedback

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Fischer, T. C.; Gagne, J.

    2014-01-01

    Active galactic nuclei (AGN) are fed by accretion of matter onto supermassive black holes (SMBHs), generating huge amounts of radiation from very small volumes. AGN also provide feedback to their environments via mass outflows of ionized gas, which could play a critical role in the formation of large-scale structure in the early Universe, chemical enrichment of the intergalactic medium, and self-regulation of SMBH and galactic bulge growth. We provide an update on our research on the winds in nearby moderate-luminosity AGN, In particular, we concentrate on winds that occur on relatively large scales (hundreds of parsecs) that are revealed through spatially resolved HST spectra of emission-line gas in the narrow line regions (NLRs) of nearby AGN. We discuss the techniques for measuring the mass outflow rates and kinetic luminosities of these AGN winds and gauge their importance for providing significant AGN feedback.

  3. Comparing Simulations of AGN Feedback

    NASA Astrophysics Data System (ADS)

    Richardson, Mark L. A.; Scannapieco, Evan; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J.; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-07-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock to well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGNs) to the simulations results in much better agreement between the methods. For our AGN model, both simulations display halo gas entropies of 100 keV cm2, similar decrements in the star formation rate, and a drop in the halo baryon content of roughly 30%. This is consistent with the AGN growth being self-regulated, regardless of the numerical method. However, the simulations with AGN feedback continue to differ in aspects that are not self-regulated, such that in SPH a larger volume of gas is impacted by feedback, and the cluster still has a lower entropy central core.

  4. New insights into AGN coronae

    NASA Astrophysics Data System (ADS)

    Lohfink, Anne; Fabian, Andrew C.; Malzac, Julien; Belmont, Renaud; Buisson, Douglas

    2016-04-01

    Active galactic nuclei (AGN) are some of the most energetic sources of radiation in the Universe. The conversion of gravitational energy into radiation is thought to take place in an accretion disk/corona system just outside the black hole. In this system thermal, UV/optical photons from the accretion disk are upscattered in a corona of hot electrons situated above the accretion disk producing X-rays. The nature of this Comptonizing corona remains a key open question in AGN physics. The NuSTAR satellite provides the opportunity to study the Comptonization spectrum produced by the corona in great detail. In our talk we will show some key results from these new studies of the Comptonization spectrum. We explore how, together with our growing knowledge of coronal sizes, we are able to draw first conclusions about the physics taking place in the corona. We find evidence for coronae to be hot and radiatively compact, putting them close to the boundary of the region in the compactness-temperature diagram which is forbidden due to runaway pair production. This suggests that pair production and annihilation are essential ingredients in the coronae of AGN and that they control the coronal temperature and shape of the observed spectra.

  5. The small observed scale of AGN-driven outflows, and inside-out disc quenching

    NASA Astrophysics Data System (ADS)

    Zubovas, Kastytis; King, Andrew

    2016-11-01

    Observations of massive outflows with detectable central active galactic nuclei (AGN) typically find them within radii ≲10 kpc. We show that this apparent size restriction is a natural result of AGN driving if this process injects total energy only of the order of the gas binding energy to the outflow, and the AGN varies over time (`flickers') as suggested in recent work. After the end of all AGN activity, the outflow continues to expand to larger radii, powered by the thermal expansion of the remnant-shocked AGN wind. We suggest that on average, outflows should be detected further from the nucleus in more massive galaxies. In massive gas-rich galaxies, these could be several tens of kpc in radius. We also consider the effect that pressure of such outflows has on a galaxy disc. In moderately gas-rich discs, with gas-to-baryon fraction <0.2, the outflow may induce star formation significant enough to be distinguished from quiescent by an apparently different normalization of the Kennicutt-Schmidt law. The star formation enhancement is probably stronger in the outskirts of galaxy discs, so coasting outflows might be detected by their effects upon the disc even after the driving AGN has shut off. We compare our results to the recent inference of inside-out quenching of star formation in galaxy discs.

  6. The Universal Unification Model of AGN

    NASA Astrophysics Data System (ADS)

    Vilkoviskij, E. Y.

    1998-12-01

    It is shown, that the model calculations of the absorption line profiles are possible in the framework of a common model both for BAL QSOs and the Seyfert galaxies with BAL. We suppose that in both cases the BAL-clouds move in the space between two conic surface, starting in the internal surface of the absorbing torus. We argue that the common nature of the intrinsic line absorption in these objects can be explained in an universal unified AGN model, where BAL AGNs are objects intermediate between AGN1 and AGN2

  7. AGNfitter: A Bayesian MCMC Approach to Fitting Spectral Energy Distributions of AGNs

    NASA Astrophysics Data System (ADS)

    Calistro Rivera, Gabriela; Lusso, Elisabeta; Hennawi, Joseph F.; Hogg, David W.

    2016-12-01

    We present AGNfitter, a publicly available open-source algorithm implementing a fully Bayesian Markov Chain Monte Carlo method to fit the spectral energy distributions (SEDs) of active galactic nuclei (AGNs) from the sub-millimeter to the UV, allowing one to robustly disentangle the physical processes responsible for their emission. AGNfitter makes use of a large library of theoretical, empirical, and semi-empirical models to characterize both the nuclear and host galaxy emission simultaneously. The model consists of four physical emission components: an accretion disk, a torus of AGN heated dust, stellar populations, and cold dust in star-forming regions. AGNfitter determines the posterior distributions of numerous parameters that govern the physics of AGNs with a fully Bayesian treatment of errors and parameter degeneracies, allowing one to infer integrated luminosities, dust attenuation parameters, stellar masses, and star-formation rates. We tested AGNfitter’s performance on real data by fitting the SEDs of a sample of 714 X-ray selected AGNs from the XMM-COSMOS survey, spectroscopically classified as Type1 (unobscured) and Type2 (obscured) AGNs by their optical-UV emission lines. We find that two independent model parameters, namely the reddening of the accretion disk and the column density of the dusty torus, are good proxies for AGN obscuration, allowing us to develop a strategy for classifying AGNs as Type1 or Type2, based solely on an SED-fitting analysis. Our classification scheme is in excellent agreement with the spectroscopic classification, giving a completeness fraction of ˜ 86 % and ˜ 70 % , and an efficiency of ˜ 80 % and ˜ 77 % , for Type1 and Type2 AGNs, respectively.

  8. Probing AGN Unification with galaxy neighbours: pitfalls and prospects

    NASA Astrophysics Data System (ADS)

    Villarroel, B.

    2015-09-01

    Statistical tests of AGN unification harbour many caveats. One way of constraining the validity of the AGN unification is through studies of close neighbours to Type-1 and Type-2 AGN. Examining thousands of AGN- galaxy pairs from the Sloan Digital Sky Survey Data Release 7 and the Galaxy Zoo project, we found that Type-2 AGN appear to reside in more star-forming environments than Type-1 AGN.

  9. Fractional randomness

    NASA Astrophysics Data System (ADS)

    Tapiero, Charles S.; Vallois, Pierre

    2016-11-01

    The premise of this paper is that a fractional probability distribution is based on fractional operators and the fractional (Hurst) index used that alters the classical setting of random variables. For example, a random variable defined by its density function might not have a fractional density function defined in its conventional sense. Practically, it implies that a distribution's granularity defined by a fractional kernel may have properties that differ due to the fractional index used and the fractional calculus applied to define it. The purpose of this paper is to consider an application of fractional calculus to define the fractional density function of a random variable. In addition, we provide and prove a number of results, defining the functional forms of these distributions as well as their existence. In particular, we define fractional probability distributions for increasing and decreasing functions that are right continuous. Examples are used to motivate the usefulness of a statistical approach to fractional calculus and its application to economic and financial problems. In conclusion, this paper is a preliminary attempt to construct statistical fractional models. Due to the breadth and the extent of such problems, this paper may be considered as an initial attempt to do so.

  10. AGN POPULATION IN HICKSON COMPACT GROUPS. I. DATA AND NUCLEAR ACTIVITY CLASSIFICATION

    SciTech Connect

    MartInez, M. A.; Del Olmo, A.; Perea, J.; Coziol, R. E-mail: chony@iaa.es E-mail: rcoziol@astro.ugto.mx

    2010-03-15

    We have conducted a new spectroscopic survey to characterize the nature of nuclear activity in Hickson compact group (HCG) galaxies and establish its frequency. We have obtained new intermediate-resolution optical spectroscopy for 200 member galaxies and corrected for underlying stellar population contamination using galaxy templates. Spectra for 11 additional galaxies have been acquired from the ESO and 6dF public archives, and emission-line ratios have been taken from the literature for 59 more galaxies. Here we present the results of our classification of the nuclear activity for 270 member galaxies, which belong to a well-defined sample of 64 HCGs. We found a large fraction of galaxies, 63%, with emission lines. Using standard diagnostic diagrams, 45% of the emission-line galaxies were classified as pure active galactic nuclei (AGNs), 23% as Transition Objects (TOs), and 32% as star-forming nuclei (SFNs). In the HCGs, the AGN activity appears as the most frequent activity type. Adopting the interpretation that in TOs a low-luminosity AGN coexists with circumnuclear star formation, the fraction of galaxies with an AGN could rise to 42% of the whole sample. The low frequency (20%) of SFNs confirms that there is no star formation enhancement in HCGs. After extinction correction, we found a median AGN H{alpha} luminosity of 7.1 x 10{sup 39} erg s{sup -1}, which implies that AGNs in HCG have a characteristically low luminosity. This result added to the fact that there is an almost complete absence of broad-line AGNs in compact groups (CGs) as found by MartInez et al. and corroborated in this study for HCGs, is consistent with very few gas left in these galaxies. In general, therefore, what may characterize the level of activity in CGs is a severe deficiency of gas.

  11. The star formation-AGN interplay in merging galaxies: insights from hydrodynamical simulations and observations.

    NASA Astrophysics Data System (ADS)

    Martinez Galarza, Juan R.; Smith, Howard Alan; Weiner, Aaron; Hayward, Christopher C.; Lanz, Lauranne; Zezas, Andreas; Rosenthal, Lee; Ashby, Matthew

    2016-01-01

    Thermal emission from an Active Galactic Nucleus (AGN) can provide a significant contribution to the bolometric luminosity of galaxies, and its effect at infrared wavelengths can mimic the process of star-formation, jeopardizing star formation rate (SFR) diagnostics. It is therefore important to model the AGN emission and to quantify its effect on the estimated SFRs when SED fitting tools are applied. We tackle this problem by studying the dust radiative transfer calculations of hydrodynamically simulated binary galaxy mergers covering a broad range of parameters, including stellar mas ratios, gas contents, AGN luminosity and viewing angles. We apply the energy balance SED fitting codes CHIBURST and CIGALE to the mock SEDs of our simulated merger, and then compare with the results of applying the same codes to the SEDs of observed merging galaxies in the Local Universe. At different stages of the interaction, we compare their derived SFRs and AGN fractions with those predicted by the hydrodynamical simulations, for a broad range of the interaction parameters, but focus on the stages near coalescence, when the AGN contribution exceed 10% of the total luminosity. We show that the contribution to IR luminosity is greatest during and immediately after coalescence, when the two supermassive black holes of the interacting pair merge and undergo and enhanced period of accretion. Under certain conditions, CIGALE succeeds at recovering the SFRs and AGN fractions with higher accuracy than other available codes, such as MAGPHYS, even during these extreme stages. Our results show that using the IR luminosity as a simple surrogate for star formation can significantly overestimate the true SFR by underestimating the contribution from the AGN. Finally, we study the effect of using different parametric star formation histories (SFHs) when fitting the SEDs of galaxies, and show that a delayed SFH is usually a reasonable choice for merging galaxies.

  12. Obscuring Fraction of Active Galactic Nuclei: Implications from Radiation-driven Fountain Models

    NASA Astrophysics Data System (ADS)

    Wada, Keiichi

    2015-10-01

    Active galactic nuclei (AGNs) are believed to be obscured by an optical thick “torus” that covers a large fraction of solid angles for the nuclei. However, the physical origin of the tori and the differences in the tori among AGNs are not clear. In a previous paper based on three-dimensional radiation-hydorodynamic calculations, we proposed a physics-based mechanism for the obscuration, called “radiation-driven fountains,” in which the circulation of the gas driven by central radiation naturally forms a thick disk that partially obscures the nuclear emission. Here, we expand this mechanism and conduct a series of simulations to explore how obscuration depends on the properties of AGNs. We found that the obscuring fraction fobs for a given column density toward the AGNs changes depending on both the AGN luminosity and the black hole mass. In particular, fobs for NH ≥ 1022 cm-2 increases from ˜0.2 to ˜0.6 as a function of the X-ray luminosity LX in the LX = 1042-44 erg s-1 range, but fobs becomes small (˜0.4) above a luminosity (˜1045 erg s-1). The behaviors of fobs can be understood by a simple analytic model and provide insight into the redshift evolution of the obscuration. The simulations also show that for a given LAGN, fobs is always smaller (˜0.2-0.3) for a larger column density (NH ≥ 1023 cm-2). We also found cases that more than 70% of the solid angles can be covered by the fountain flows.

  13. Mass spectrometry analyses of κ and λ fractions result in increased number of complementarity-determining region identifications.

    PubMed

    Broodman, Ingrid; de Costa, Dominique; Stingl, Christoph; Dekker, Lennard J M; VanDuijn, Martijn M; Lindemans, Jan; van Klaveren, Rob J; Luider, Theo M

    2012-01-01

    Sera from lung cancer patients contain antibodies against tumor-associated antigens. Specific amino acid sequences of the complementarity-determining regions (CDRs) in the antigen-binding fragment (Fab) of these antibodies have potential as lung cancer biomarkers. Detection and identification of CDRs by mass spectrometry can significantly be improved by reduction of the complexity of the immunoglobulin molecule. Our aim was to molecular dissect IgG into κ and λ fragments to reduce the complexity and thereby identify substantially more CDRs than by just total Fab isolation. We purified Fab, Fab-κ, Fab-λ, κ and λ light chains from serum from 10 stage I lung adenocarcinoma patients and 10 matched controls from the current and former smokers. After purification, the immunoglobulin fragments were enzymatically digested and measured by high-resolution mass spectrometry. Finally, we compared the number of CDRs identified in these immunoglobulin fragments with that in the Fab fragments. Twice as many CDRs were identified when Fab-κ, Fab-λ, κ and λ (3330) were combined than in the Fab fraction (1663) alone. The number of CDRs and κ:λ ratio was statistically similar in both cases and controls. Molecular dissection of IgG identifies significantly more CDRs, which increases the likelihood of finding lung cancer-related CDR sequences.

  14. Improvement of wear and adherence properties of composite coatings by a gradual increase in particle volume fraction

    SciTech Connect

    Ding, X.M.; Merk, N.

    1997-09-01

    Electrodeposited composites (ECs) are thin composite deposits made of a base metal or alloy which is reinforced by second phase particles of ceramic, polymer or graphite. ECs are produced rather inexpensively at temperatures below 60 C, where no strong interfacial reaction may occur and residual thermal stresses are negligible. Electrodeposited composites play an important role in tailoring the surface properties of bulk materials. Indeed, ECs containing particle volume fractions (PVF) up to 30% of hard ceramic particles exhibit superior hardness and wear resistance compared with pure metallic deposits and are therefore used as wear-resistant coatings. However, as the inert particles are not adhesive to the substrates, an increase in PVF is often accompanied by a decrease in adherence of the coating to the substrate. Furthermore, a high PVF is often accompanied by a dramatic loss of functional property, gradient composite coatings having a lower PVF at the substrate side and a higher PVF at the surface side of ECs is produced. In this work the authors present the wear and adhesion behavior of such gradient coatings. The matrix was either Cu or Ni and the second phase particles were alumina and silicon carbide.

  15. Increased Left Ventricular Stiffness Impairs Exercise Capacity in Patients with Heart Failure Symptoms Despite Normal Left Ventricular Ejection Fraction

    PubMed Central

    Sinning, David; Kasner, Mario; Westermann, Dirk; Schulze, Karsten; Schultheiss, Heinz-Peter; Tschöpe, Carsten

    2011-01-01

    Aims. Several mechanisms can be involved in the development of exercise intolerance in patients with heart failure despite normal left ventricular ejection fraction (HFNEF) and may include impairment of left ventricular (LV) stiffness. We therefore investigated the influence of LV stiffness, determined by pressure-volume loop analysis obtained by conductance catheterization, on exercise capacity in HFNEF. Methods and Results. 27 HFNEF patients who showed LV diastolic dysfunction in pressure-volume (PV) loop analysis performed symptom-limited cardiopulmonary exercise testing (CPET) and were compared with 12 patients who did not show diastolic dysfunction in PV loop analysis. HFNEF patients revealed a lower peak performance (P = .046), breathing reserve (P = .006), and ventilation equivalent for carbon dioxide production at rest (P = .002). LV stiffness correlated with peak oxygen uptake (r = −0.636, P < .001), peak oxygen uptake at ventilatory threshold (r = −0.500, P = .009), and ventilation equivalent for carbon dioxide production at ventilatory threshold (r = 0.529, P = .005). Conclusions. CPET parameters such as peak oxygen uptake, peak oxygen uptake at ventilatory threshold, and ventilation equivalent for carbon dioxide production at ventilatory threshold correlate with LV stiffness. Increased LV stiffness impairs exercise capacity in HFNEF. PMID:21403885

  16. Semi-empirical AGN detection threshold in spectral synthesis studies of Lyman-continuum-leaking early-type galaxies

    NASA Astrophysics Data System (ADS)

    Cardoso, Leandro S. M.; Gomes, Jean-Michel; Papaderos, Polychronis

    2016-10-01

    Various lines of evidence suggest that the cores of a large portion of early-type galaxies (ETGs) are virtually evacuated of warm ionised gas. This implies that the Lyman-continuum (LyC) radiation produced by an assumed active galactic nucleus (AGN) can escape from the nuclei of these systems without being locally reprocessed into nebular emission, which would prevent their reliable spectroscopic classification as Seyfert galaxies with standard diagnostic emission-line ratios. The spectral energy distribution (SED) of these ETGs would then lack nebular emission and be essentially composed of an old stellar component and the featureless power-law (PL) continuum from the AGN. A question that arises in this context is whether the AGN component can be detected with current spectral population synthesis in the optical, specifically, whether these techniques effectively place an AGN detection threshold in LyC-leaking galaxies. To quantitatively address this question, we took a combined approach that involves spectral fitting with Starlight of synthetic SEDs composed of stellar emission that characterises a 10 Gyr old ETG and an AGN power-law component that contributes a fraction 0 ≤ xAGN < 1 of the monochromatic luminosity at λ0 = 4020 Å. In addition to a set of fits for PL distributions Fν ∝ ν- α with the canonical α = 1.5, we used a base of multiple PLs with 0.5 ≤ α ≤ 2 for a grid of synthetic SEDs with a signal-to-noise ratio of 5-103. Our analysis indicates an effective AGN detection threshold at xAGN ≃ 0.26, which suggests that a considerable fraction of ETGs hosting significant accretion-powered nuclear activity may be missing in the AGN demographics.

  17. Astrometric Evidence for a Population of Dislodged AGNs

    NASA Astrophysics Data System (ADS)

    Makarov, Valeri V.; Frouard, Julien; Berghea, Ciprian T.; Rest, Armin; Chambers, Kenneth C.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.

    2017-02-01

    We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources and their optical counterparts is strongly non-Gaussian, with powerful wings extending beyond 1 arcsec. Limiting our analysis to only high-confidence difference detections, we find (and publish) a list of 188 objects with normalized variances above 12 and offsets below 1 arcsec. Pan-STARRS stacked and monochromatic images resolve some of these sources, indicating the presence of double sources, confusion sources, or pronounced extended structures. Some 89 high-quality objects, however, do not show any perturbations and appear to be star-like single sources, yet they are displaced by multiples of the expected error from the radio-loud AGN. We conclude that a fraction of luminous AGNs (more than 4%) can be physically dislodged from the optical centers of their parent galaxies.

  18. The ACAT inhibitor avasimibe increases the fractional clearance rate of postprandial triglyceride-rich lipoproteins in miniature pigs.

    PubMed

    Burnett, John R; Telford, Dawn E; Barrett, P Hugh R; Huff, Murray W

    2005-12-30

    Previously, we have shown, in vivo, that the acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitor avasimibe decreases hepatic apolipoprotein (apo) B secretion into plasma. To test the hypothesis that avasimibe modulates postprandial triglyceride-rich lipoprotein (TRL) metabolism in vivo, an oral fat load (2 g fat/kg) containing retinol was given to 9 control miniature pigs and to 9 animals after 28 days treatment with avasimibe (10 mg/kg/day, n=5; 25 mg/kg/day, n=4). The kinetic parameters for plasma retinyl palmitate (RP) metabolism were determined by multi-compartmental modeling using SAAM II. Avasimibe decreased the 2-h TRL (d<1.006 g/mL; S(f)>20) triglyceride concentrations by 34%. The TRL triglyceride 0-12 h area under the curve (AUC) was decreased by 21%. In contrast, avasimibe had no effect on peak TRL RP concentrations, time to peak, or its rate of appearance into plasma, however, the TRL RP 0-12 h AUC was decreased by 17%. Analysis of the RP kinetic parameters revealed that the TRL fractional clearance rate (FCR) was increased 1.4-fold with avasimibe. The TRL RP FCR was negatively correlated with very low density lipoprotein (VLDL) apoB production rate measured in the fasting state (r=-0.504). No significant changes in total intestinal lipid concentrations were observed. Thus, although avasimibe had no effect on intestinal TRL secretion, plasma TRL clearance was significantly increased; an effect that may relate to a decreased competition with hepatic VLDL for removal processes.

  19. CANDELS: CONSTRAINING THE AGN-MERGER CONNECTION WITH HOST MORPHOLOGIES AT z {approx} 2

    SciTech Connect

    Kocevski, Dale D.; Faber, S. M.; Mozena, Mark; Trump, Jonathan R.; Koo, David C.; Nandra, Kirpal; Brusa, Marcella; Wuyts, Stijn; Rangel, Cyprian; Laird, Elise S.; Bell, Eric F.; Alexander, David M.; Bournaud, Frederic; Conselice, Christopher J.; Dekel, Avishai; and others

    2012-01-10

    Using Hubble Space Telescope/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we examine the role that major galaxy mergers play in triggering active galactic nucleus (AGN) activity at z {approx} 2. Our sample consists of 72 moderate-luminosity (L{sub X} {approx} 10{sup 42-44} erg s{sup -1}) AGNs at 1.5 < z < 2.5 that are selected using the 4 Ms Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift. We find that most of the AGNs reside in disk galaxies (51.4{sup +5.8}{sub -5.9}%), while a smaller percentage are found in spheroids (27.8{sup +5.8}{sub -4.6}%). Roughly 16.7{sup +5.3}{sub -3.5}% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction, while most of the hosts (55.6{sup +5.6}{sub -5.9}%) appear relatively relaxed and undisturbed. These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances. These results suggest that the hosts of moderate-luminosity AGNs are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z {approx} 2. The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z {approx} 2, even at moderate X-ray luminosities. Although we cannot rule out that minor mergers are responsible for triggering these systems, the presence of a large population of relatively undisturbed disk-like hosts suggests that the stochastic accretion of gas plays a greater role in fueling AGN activity at z {approx} 2 than previously thought.

  20. SWIFT BAT Survey of AGN

    NASA Technical Reports Server (NTRS)

    Tueller, J.; Mushotzky, R. F.; Barthelmy, S.; Cannizzo, J. K.; Gehrels, N.; Markwardt, C. B.; Skinner, G. K.; Winter, L. M.

    2008-01-01

    We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.

  1. Spectral Energy Distributions of Quasars and AGN

    NASA Astrophysics Data System (ADS)

    Wilkes, B.

    2004-06-01

    Active Galactic Nuclei (AGN) are multiwavelength emitters. To have any hope of understanding them, or even to determine their energy output, we must observe them in multiple wavebands using many telescopes. I will review what we have learned from broad-band observations of relatively bright, low-redshift AGN over the past ˜ 15 years. AGN can be found at all wavelengths but each provides a different view of the intrinsic population, often with little overlap between samples selected in different wavebands. I look forward to the full view of the intrinsic population which we will obtain over the next few years with surveys using today's new, sensitive observatories. These surveys are already finding enough new and different AGN candidates to pose the question ``What IS an AGN?".

  2. Early Idiopathic Normal Pressure Hydrocephalus Patients With Neuropsychological Impairment Are Associated With Increased Fractional Anisotropy in the Anterior Thalamic Nucleus.

    PubMed

    Chen, Yung-Chieh; Chiang, Shih-Wei; Chi, Chia-Hsing; Liou, Michelle; Kuo, Duen-Pang; Kao, Hung-Wen; Chung, Hsiao-Wen; Ma, Hsin I; Peng, Giia-Sheun; Wu, Yu-Te; Chen, Cheng-Yu

    2016-05-01

    In this study, we aimed to investigate the reactive changes in diffusion tensor imaging (DTI)-derived diffusion metrics of the anterior thalamic nucleus (AN), a relaying center for the Papez circuit, in early idiopathic normal pressure hydrocephalus (iNPH) patients with memory impairment, as well as its correlation with the patients' neuropsychological performances. In total, 28 probable iNPH patients with symptom onset within 1 year and 17 control subjects were prospectively recruited between 2010 and 2013 for this institutional review board-approved study. Imaging studies including DTI and a neuropsychological assessment battery were performed in all subjects. Diffusion metrics were measured from the region of the AN using tract-deterministic seeding method by reconstructing the mammillo-thalamo-cingulate connections within the Papez circuit. Differences in diffusion metrics and memory assessment scores between the patient and control group were examined via the Mann-Whitney U test. Spearman correlation analyses were performed to examine associations between diffusion metrics of AN and neuropsychological tests within the patient group. We discovered that early iNPH patients exhibited marked elevations in fractional anisotropy, pure diffusion anisotropy, and axial diffusivity (all P < 0.01), as well as lower neuropsychological test scores including verbal and nonverbal memory (all P < 0.05) compared with normal control. Spearman rank correlation analyses did not disclose significant correlations between AN diffusion metrics and neuropsychological test scores in the patient group, whereas ranked scatter plots clearly demonstrated a dichotic sample distribution between patient and control samples. In summary, our study highlighted the potential compensatory role of the AN by increasing thalamocortical connectivity within the Papez circuit because memory function declines in early iNPH when early shunt treatment may potentially reverse the memory deficits.

  3. Early Idiopathic Normal Pressure Hydrocephalus Patients With Neuropsychological Impairment Are Associated With Increased Fractional Anisotropy in the Anterior Thalamic Nucleus

    PubMed Central

    Chen, Yung-Chieh; Chiang, Shih-Wei; Chi, Chia-Hsing; Liou, Michelle; Kuo, Duen-Pang; Kao, Hung-Wen; Chung, Hsiao-Wen; Ma, Hsin I.; Peng, Giia-Sheun; Wu, Yu-Te; Chen, Cheng-Yu

    2016-01-01

    Abstract In this study, we aimed to investigate the reactive changes in diffusion tensor imaging (DTI)-derived diffusion metrics of the anterior thalamic nucleus (AN), a relaying center for the Papez circuit, in early idiopathic normal pressure hydrocephalus (iNPH) patients with memory impairment, as well as its correlation with the patients’ neuropsychological performances. In total, 28 probable iNPH patients with symptom onset within 1 year and 17 control subjects were prospectively recruited between 2010 and 2013 for this institutional review board-approved study. Imaging studies including DTI and a neuropsychological assessment battery were performed in all subjects. Diffusion metrics were measured from the region of the AN using tract-deterministic seeding method by reconstructing the mammillo–thalamo–cingulate connections within the Papez circuit. Differences in diffusion metrics and memory assessment scores between the patient and control group were examined via the Mann–Whitney U test. Spearman correlation analyses were performed to examine associations between diffusion metrics of AN and neuropsychological tests within the patient group. We discovered that early iNPH patients exhibited marked elevations in fractional anisotropy, pure diffusion anisotropy, and axial diffusivity (all P < 0.01), as well as lower neuropsychological test scores including verbal and nonverbal memory (all P < 0.05) compared with normal control. Spearman rank correlation analyses did not disclose significant correlations between AN diffusion metrics and neuropsychological test scores in the patient group, whereas ranked scatter plots clearly demonstrated a dichotic sample distribution between patient and control samples. In summary, our study highlighted the potential compensatory role of the AN by increasing thalamocortical connectivity within the Papez circuit because memory function declines in early iNPH when early shunt treatment may potentially reverse the

  4. THE BULK OF THE BLACK HOLE GROWTH SINCE z {approx} 1 OCCURS IN A SECULAR UNIVERSE: NO MAJOR MERGER-AGN CONNECTION

    SciTech Connect

    Cisternas, Mauricio; Jahnke, Knud; Inskip, Katherine J.; Robaina, Aday R.; Andrae, Rene; Kartaltepe, Jeyhan; Koekemoer, Anton M.; Lisker, Thorsten; Scodeggio, Marco; Sheth, Kartik; Capak, Peter; Trump, Jonathan R.; Impey, Chris D.; Miyaji, Takamitsu; Lusso, Elisabeta; Brusa, Marcella; Cappelluti, Nico; Civano, Francesca; Ilbert, Olivier; Leauthaud, Alexie

    2011-01-10

    What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGNs) activity? To answer this long-standing question, we analyze 140 XMM-Newton-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z {approx} 0.3-1.0 and M{sub *} < 10{sup 11.7} M{sub sun} with high-resolution Hubble Space Telescope/Advanced Camera for Surveys imaging from the COSMOS field. The visual analysis of their morphologies by 10 independent human classifiers yields a measure of the fraction of distorted morphologies in the AGN and control samples, i.e., quantifying the signature of recent mergers which might potentially be responsible for fueling/triggering the AGN. We find that (1) the vast majority (>85%) of the AGN host galaxies do not show strong distortions and (2) there is no significant difference in the distortion fractions between active and inactive galaxies. Our findings provide the best direct evidence that, since z {approx} 1, the bulk of black hole (BH) accretion has not been triggered by major galaxy mergers, therefore arguing that the alternative mechanisms, i.e., internal secular processes and minor interactions, are the leading triggers for the episodes of major BH growth. We also exclude an alternative interpretation of our results: a substantial time lag between merging and the observability of the AGN phase could wash out the most significant merging signatures, explaining the lack of enhancement of strong distortions on the AGN hosts. We show that this alternative scenario is unlikely due to (1) recent major mergers being ruled out for the majority of sources due to the high fraction of disk-hosted AGNs, (2) the lack of a significant X-ray signal in merging inactive galaxies as a signature of a potential buried AGN, and (3) the low levels of soft X-ray obscuration for AGNs hosted by interacting galaxies, in contrast to model predictions.

  5. AGN Accretion Physics: Insights from K2

    NASA Astrophysics Data System (ADS)

    Vogeley, Michael

    We propose to use Kepler K2 mission observations of 1800 supermassive black holes at the centers of galaxies (Active Galactic Nuclei; AGN) to test models for accretion physics, to study the relationship between variability and other AGN properties such as accretion rate, and to guide methods for detecting and classifying AGN in future time-domain surveys. AGN exhibit optical brightness fluctuations on timescales from below an hour up to many years. These fluctuations are determined by the physics of accretion of matter onto black holes from their galactic environment. By observing variability on timescales down to below an hour, Kepler probes the accretion region on length scales that are too small to be directly imaged using conventional telescopes. These data allow us to test competing models for accretion physics that make different predictions for the statistics of variability. Our previous work provides strong evidence that models of AGN variability that work on long timescale data are not adequate to describe the full range of fluctuation timescales probed by Kepler. We will analyze the light curves of 1800 AGN that have been monitored by Kepler during recent and ongoing K2 campaigns. These objects span a large range of luminosity and AGN type, thus allowing study of the relationship between variability and other physical properties. We will characterize the statistics of AGN variability using state-of-the-art methods of time series analysis that are appropriate for quantifying the stochastic behavior of AGN. This analysis builds on our previous work in which we developed and tested new analysis software that extracts the full information content of these light curves and will enable several key outcomes: (1) Measurement of the relationship between types of AGN and their variability. (2) Tests for dependence of variability on accretion rate. (3) Investigation of changes in variability behavior that point to changes in the mode of accretion. (4) Correlations

  6. Plants increase arsenic in solution but decrease the non-specifically bound fraction in the rhizosphere of an alkaline, naturally rich soil.

    PubMed

    Obeidy, Carole; Bravin, Matthieu N; Bouchardon, Jean-Luc; Conord, Cyrille; Moutte, Jacques; Guy, Bernard; Faure, Olivier

    2016-04-01

    We aimed at determining the major physical-chemical processes that drive arsenic (As) dynamic in the rhizosphere of four species (Holcus lanatus, Dittrichia viscosa, Lotus corniculatus, Plantago lanceolata) tested for phytostabilization. Experiments were performed with an alkaline soil naturally rich in As. Composition of the soil solution of planted and unplanted pots was monitored every 15 days for 90 days, with a focus on the evolution of As concentrations in solution and in the non-specifically bound (i.e. easily exchangeable) fraction. The four species similarly increased As concentration in solution, but decreased As concentration in the non-specifically bound fraction. The major part (60%) of As desorbed from the non-specifically bound fraction in planted pots was likely redistributed on the less available fractions of As on the solid phase. A second part (35%) of desorbed As was taken up by plants. The minor part (5%) of desorbed As supplied As increase in solution. To conclude, plants induced a substantial redistribution of As on the less available fractions in the rhizosphere, as expected in phytostabilization strategies. Plants however concomitantly increased As concentration in the rhizosphere solution which may contribute to As transfer through plant uptake and leaching.

  7. Exploring the Vertical Structure of Nuclear Starburst Disks: A Possible Source of AGN Obscuration at Redshift ~ 1

    NASA Astrophysics Data System (ADS)

    Gohil, Raj; Ballantyne, David R.

    2017-01-01

    Nuclear starburst disks (NSDs) are star-forming regions that could be present at high redshift (z~1) in the vicinity of active galactic nuclei (AGNs). One dimensional analytical models by Thompson et al. (2005) show that, under certain conditions, these disks can be geometrically thick on parsec scales which make them a possible source for AGN obscuration. We construct a 2D model of NSDs where an iterative method is used to obtain vertical solutions for a given annulus. These solutions coherently satisfy the equations of energy balance, hydrostatic, radiative transfer, and the Toomre stability criteria. In comparison to 1D model, a more robust 2D calculation shows the higher scale-height at the outer part of a NSD, but predicts a lower expansion of an atmosphere at the parsec/sub-parsec scale. A total of 96 NSD models are computed under various physical conditions (black hole mass, size of a disk, and a gas fraction) in order to predict the column density distribution along a line of sight. Assuming a random distribution of input parameters, the statistics yield 59% of Type 1, 24% of Compton-thin (CTN), and 17% of Compton-thick (CTK) AGNs. The distribution of obscured AGNs fraction peaks near NH = 1023.5 cm-2. Depending on a viewing angle (θ) of a given NSD, the line of sight NH can vary from 1022 to 1028 cm-2. This supports the unification theory of AGNs as our results show an AGN can appear to be obscured by a CTK (NH > 1024 cm-2) or CTN (1022 cm-2< NH < 1024 cm-2) gas depending on a viewing angle. Using 2D structure, we show any θ is possible for CTN AGNs; however, the maximum allowed θ for CTK AGN is restricted to approximately 60 degrees.

  8. A Hubble Space Telescope Survey of Intrinsic Absorption in Nearby AGN

    NASA Astrophysics Data System (ADS)

    Dashtamirova, Dzhuliya; Dunn, Jay P.; Crenshaw, D. Michael

    2017-01-01

    We present a survey of the intrinsic UV absorption lines in active galactic nuclei (AGN). We limit our study to the ultraviolet spectra of type 1 AGN with a redshift of z < 0.15 as a continuation of the Dunn et al. (2007, 2008) and Crenshaw et al. (1999) studies of smaller samples. We identify approximately 90 AGN fit our redshift specifications in the Mikulski Archive for Space Telescopes (MAST) database with Cosmic Origin Spectrograph (COS) observations. We download and co-add all of the COS spectra. We find that about 80 of these are type 1 AGN. We normalize the COS spectra and identify all of the intrinsic Lyman-alpha, N V, Si IV, and C IV intrinsic absorption features. From these data, we determine the fraction of type 1 AGN with intrinsic absorption in this redshift range and find the global covering factors of the absorbers. We also identify low ionization species as well as excited state lines. A number of objects have multiple epoch COS and/or Space Telescope Imaging Spectrograph (STIS) observations, which we use to investigate the absorption variability.

  9. Resolving AGN with PanSTARRS transients

    NASA Astrophysics Data System (ADS)

    Lawrence, Andy

    2012-10-01

    With PanSTARRS we have discovered a new class of slow, blue nuclear transients which we believe to be rare examples of background AGN microlensed by stars in foreground galaxies, amplified by a factor of 10--100. The background AGN should be somewhat resolved by the foreground lens, providing a unique new diagnostic of AGN size and structure - the UV, optical, IR, BLR, and X-ray regions should have differing evolutions during the event. This proposal is a first step towards understanding the structure of the X-ray source : testing the microlensing hypothesis, characterising the SED, and establishing the first two epochs in an expected gradual decline.

  10. Probing Agn Accretion Physics With Kepler

    NASA Astrophysics Data System (ADS)

    Vogeley, Michael

    We propose to use Kepler observations of a sample of ~100 supermassive black holes at the centers of galaxies (Active Galactic Nuclei; AGN) to test models for accretion physics, to study the relationship between variability and other AGN properties, and to guide methods for detecting and classifying AGN in future time-domain surveys. AGN exhibit optical brightness fluctuations on timescales from below an hour up to many years. These fluctuations are determined by the physics of accretion of matter onto black holes from their galactic environment. By observing variability on timescales down to below an hour, Kepler probes the accretion region on length scales that are too small to be directly imaged using conventional telescopes. Data from this unique time- domain telescope now allow us to test competing models for accretion physics that make different predictions for the statistics of variability. Preliminary work provides strong evidence that models of AGN variability that work on long timescale data are not adequate to describe the full range of fluctuation timescales probed by Kepler. We will analyze the light curves of Kepler AGN that span a large range of luminosity and AGN type, thus allowing study of the relationship between variability and other physical properties. Using methods developed and tested by the Kepler team, we will perform custom post-processing of these light curves to remove known systematics. Statistical analyses of the AGN light curves will include estimation of the Structure Function, which quantifies the correlations of brightness fluctuations, and maximum likelihood light curve reconstruction. Competing models for the stochastic behavior of AGN will be tested to evaluate which models best describe variability of AGN over the full range of timescales probed by Kepler. Correlations between the stochastic model parameters and physical parameters will provide new methods for classification of AGN from their variability and aid in

  11. A Multi-Frequency Study of an X-ray Selected Sample of AGN II: Line Emission Studies and the X-ray Luminosity Function

    NASA Astrophysics Data System (ADS)

    Grossan, B.; Remillard, R.; Bradt, H.

    1992-12-01

    We carried out a multi-frequency study of a flux-limited (0.95 mu Jy @ 5 keV) sample of 96 emission-line AGN taken from the HEAO-1 LASS/MC survey. Preliminary results of this study were presented at the Jan. 1992 meeting. Here we present new results from line emission and continuum studies and more details regarding the AGN X-ray luminosity functions (XLFs). We find that narrow [OIII] flux correlates well with X-ray flux. This result is consistent with a simple picture where the photoionizing continuum is distributed over a large solid angle in the narrow line region, and is closely related to the X-ray continuum. Broad Balmer lines do not demonstrate a strong correlation with X-ray flux. The UV continuum ( ~ 1400 Angstroms) does not correlate with any optical line emission we measured, but UV variability could have affected this result. In contrast, we find very strong correlations of high-ionization UV broad line fluxes and the simultaneously measured UV continuum. The geometry and/or obscuration effects in the broad line region may therefore be different than those in the narrow line region. A very large spread in the value of broad line Balmer decrements (Hβ /Hα = 0.13 - 0.40) was observed among objects determined to be un-reddened by the lack of an absorption feature at 2175 Angstroms. If there were an intrinsic Balmer decrement for the broad line regions in AGN, the smallest Hβ /Hα values would correspond to extreme values of reddening (E(B-V) > 1 mag). Therefore, we conclude that the broad line Balmer decrement cannot be used in determining continuum reddening in most AGN. We find that the AGN 2-10 keV XLF is roughly a power law, but steepens with increasing luminosity, and turns over below 10(42) erg s(-1) . The XLF of Seyfert 2's resembles a power law from 10(42) - 10(43.5) erg s(-1) , but at higher luminosity, the XLF steepens. In this sample, the cumulative fraction of Seyfert 2's falls rapidly with luminosity, and the overall fraction of Seyfert 2's

  12. The MIXR sample: AGN activity versus star formation across the cross-correlation of WISE, 3XMM, and FIRST/NVSS

    NASA Astrophysics Data System (ADS)

    Mingo, B.; Watson, M. G.; Rosen, S. R.; Hardcastle, M. J.; Ruiz, A.; Blain, A.; Carrera, F. J.; Mateos, S.; Pineau, F.-X.; Stewart, G. C.

    2016-11-01

    We cross-correlate the largest available mid-infrared (Wide-field Infrared Survey Explorer - WISE), X-ray (3XMM) and radio (Faint Images of the Radio Sky at Twenty centimetres+NRAO VLA Sky Survey) catalogues to define the MIXR sample of AGN and star-forming galaxies. We pre-classify the sources based on their positions on the WISE colour/colour plot, showing that the MIXR triple selection is extremely effective to diagnose the star formation and AGN activity of individual populations, even on a flux/magnitude basis, extending the diagnostics to objects with luminosities and redshifts from SDSS DR12. We recover the radio/mid-IR star formation correlation with great accuracy, and use it to classify our sources, based on their activity, as radio-loud and radio-quiet active galactic nuclei (AGN), low excitation radio galaxies/low ionization nuclear emission line regions, and non-AGN galaxies. These diagnostics can prove extremely useful for large AGN and galaxy samples, and help develop ways to efficiently triage sources when data from the next generation of instruments becomes available. We study bias in detail, and show that while the widely used WISE colour selections for AGN are very successful at cleanly selecting samples of luminous AGN, they miss or misclassify a substantial fraction of AGN at lower luminosities and/or higher redshifts. MIXR also allows us to test the relation between radiative and kinetic (jet) power in radio-loud AGN, for which a tight correlation is expected due to a mutual dependence on accretion. Our results highlight that long-term AGN variability, jet regulation, and other factors affecting the Q/Lbol relation, are introducing a vast amount of scatter in this relation, with dramatic potential consequences on our current understanding of AGN feedback and its effect on star formation.

  13. ISO Key Project: Exploring the Full Range of Quasar/AGN Properties

    NASA Technical Reports Server (NTRS)

    Wilkes, B.

    2001-01-01

    The origin of the infrared emission in Active Galactic Nuclei (AGN), whose strength is comparable to the optical/ultra-violet (OUV) emission, is generally thought to be a combination of thermal emission from dust and non-thermal, synchrotron emission. Although data are sparse, particularly in the far-infrared, the broad wavelength range of this emission suggests a wide range of temperatures and a combination of AGN and starburst heating mechanisms. The strength of the non-thermal emission is expected to be related to the radio emission. While this scenario is well-established, basic questions, such as the spatial and temperature distribution of the dust, the relative importance of AGN and starburst heating, and the significance of the non-thermal contribution, remain largely undetermined. The wide wavelength range of the Infrared Space Observatory (ISO) combined with its arcmin spatial resolution and increased sensitivity facilitated the observation of a larger subset of the AGN population than previously covered, allowing these questions to be investigated in more detail. This paper will review the spectral energy distributions (SED) of AGN with particular emphasis on the infrared emission and on ISO contributions to our knowledge. Preliminary results from ISO observations of X-ray selected and high-redshift AGN will be described.

  14. A statistical study of H i gas in nearby narrow-line AGN-hosting galaxies

    SciTech Connect

    Zhu, Yi-Nan; Wu, Hong E-mail: hwu@bao.ac.cn

    2015-01-01

    As a quenching mechanism, active galactic nucleus (AGN) feedback could suppress on going star formation in host galaxies. On the basis of a sample of galaxies selected from the Arecibo Legacy Fast ALFA (ALFALFA) H i survey, the dependence of the H i mass (M{sub H} {sub i}), stellar mass (M{sub *}), and H i-to-stellar mass ratio (M{sub H} {sub i}/M{sub *}) on various tracers of AGN activity are presented and analyzed in this paper. Almost all the AGN hostings in this sample are gas-rich galaxies, and there is not any evidence to indicate that the AGN activity could increase or decrease either M{sub H} {sub i} or M{sub H} {sub i}/M{sub *}. The position of the cold neutral gas cannot be fixed accurately based only on available H i data, due to the large beam size of ALFALFA survey. In addition, even though AGN hostings are more easily detected by an H i survey compared with absorption line galaxies, these two types of galaxies show similar star formation history. If an AGN hosting would ultimately evolve into an old red galaxy with low cold gas, then when and how the gas has been exhausted must be solved by future hypotheses and observations.

  15. First Detections of Compact AGN-triggered Radio Cores in RQ AGNs in the ECDFS

    NASA Astrophysics Data System (ADS)

    Prandoni, I.; Maini, A.; Norris, R. P.; Giovannini, G.; Spitler, L. R.

    2016-08-01

    The mechanism triggering the radio emission in Radio-Quiet (RQ) Active Galactic Nuclei (AGN), found to be a relevant component of the faint radio population in deep fields, is hotly debated. Most RQ AGNs are unresolved or barely resolved at a few arcsec scale, comparable to the host galaxy size. RQ AGNs have also been found to share many properties with Star Forming Galaxies (SFG). They have similar radio luminosities and similar optical- /infrared-to-radio flux ratios. Their radio luminosity functions show similar evolutionary trends, and their host galaxies have similar colours, optical morphologies and stellar masses. For all these reasons it was concluded that the radio emission in such RQ AGNs is mainly triggered by star formation (SF). However in the local Universe (z<0.5) it is well known that both AGN and SF processes can contribute to the total radio emission in RQ AGNs (see e.g., Seyfert 2 galaxies), and there is growing evidence that composite SF/AGN systems are common at mid to high redshift (z>1-2). We used the Australian Long Baseline Array to observe a number of RQ AGNs in the Extended Chandra Deep Field South (ECDFS), and we detected compact, high-surface-brightness radio cores in some of them. Our pilot study shows that at least some of the sources classified as radio quiet contain an AGN that can contribute significantly (~50% or more) to the total radio emission. This is a first direct evidence of the presence of such AGN-triggered radio emission in RQ AGNs at cosmological redshifts.

  16. Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies

    NASA Astrophysics Data System (ADS)

    Gürkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Smith, D. J. B.; Bourne, N.; Dunne, L.; Maddox, S.; Ivison, R. J.; Fritz, J.

    2015-10-01

    We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-μm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O III] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-μm luminosity and stellar mass measurements from the Sloan Digital Sky Survey-Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass.

  17. Delving into X-Ray Obscuration of Type 2 AGN, Near and Far

    NASA Technical Reports Server (NTRS)

    Lamassa, Stephanie M.; Yaqoob, Tahir; Ptak, Andrew F.; Jia, Jianjun; Heckman, Timothy M.; Gandhi, Poshak; Urry, C. Meg

    2014-01-01

    Using self-consistent, physically motivated models, we investigate the X-ray obscuration in 19 Type 2 [O iii] 5007Å selected active galactic nuclei (AGNs), 9 of which are local Seyfert 2 galaxies and 10 of which are Type 2 quasar candidates. We derive reliable line-of-sight and global column densities for these objects, which is the first time this has been reported for an AGN sample; four AGNs have significantly different global and line-of-sight column densities. Five sources are heavily obscured to Compton-thick. We comment on interesting sources revealed by our spectral modeling, including a candidate "naked" Sy2. After correcting for absorption, we find that the ratio of the rest-frame, 2-10 keV luminosity (L2-10 keV,in) to L[O iii] is 1.54 +/- 0.49 dex which is essentially identical to the mean Type 1 AGN value. The Fe K(alpha) luminosity is significantly correlated with L[O iii] but with substantial scatter. Finally, we do not find a trend between L2-10 keV,in and global or line-of-sight column density, between column density and redshift, between column density and scattering fraction, or between scattering fraction and redshift. Key words: galaxies: active - galaxies: Seyfert - X-rays: general

  18. Delving into X-ray obscuration of type 2 AGN, near and far

    SciTech Connect

    LaMassa, Stephanie M.; Meg Urry, C.; Yaqoob, Tahir; Ptak, Andrew F.; Gandhi, Poshak

    2014-05-20

    Using self-consistent, physically motivated models, we investigate the X-ray obscuration in 19 Type 2 [O III] 5007 Å selected active galactic nuclei (AGNs), 9 of which are local Seyfert 2 galaxies and 10 of which are Type 2 quasar candidates. We derive reliable line-of-sight and global column densities for these objects, which is the first time this has been reported for an AGN sample; four AGNs have significantly different global and line-of-sight column densities. Five sources are heavily obscured to Compton-thick. We comment on interesting sources revealed by our spectral modeling, including a candidate 'naked' Sy2. After correcting for absorption, we find that the ratio of the rest-frame, 2-10 keV luminosity (L{sub 2-10} {sub keV,} {sub in}) to L{sub [O} {sub III]} is 1.54 ± 0.49 dex which is essentially identical to the mean Type 1 AGN value. The Fe Kα luminosity is significantly correlated with L{sub [O} {sub III]} but with substantial scatter. Finally, we do not find a trend between L {sub 2-10keV,} {sub in} and global or line-of-sight column density, between column density and redshift, between column density and scattering fraction, or between scattering fraction and redshift.

  19. The view of AGN-host alignment via reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Middleton, Matthew J.; Parker, Michael L.; Reynolds, Christopher S.; Fabian, Andrew C.; Lohfink, Anne M.

    2016-04-01

    The fuelling of active galactic nuclei (AGN) - via material propagated through the galactic disc or via minor mergers - is expected to leave an imprint on the alignment of the sub-pc disc relative to the host galaxy's stellar disc. Determining the inclination of the inner disc usually relies on the launching angle of the jet; here instead we use the inclination derived from reflection fits to a sample of AGN. We determine the distorting effect of unmodelled Fe XXV/XXVI features and, via extensive simulations, determine the difference in disc inclination resulting from the use of RELXILL compared to REFLIONX. We compare inner disc inclinations to those for the host galaxy stellar disc derived from the Hubble formula and, via Monte Carlo simulations, find a strong lack of a correlation (at ≫5σ) implying either widespread feeding via mergers if we assume the sample to be homogeneous, or that radiative disc warps are distorting our view of the emission. However, we find that by removing a small (˜1/5) subset of AGN, the remaining sample is consistent with random sampling of an underlying 1:1 correlation (at the 3σ level). A heterogenous sample would likely imply that our view is not dominated by radiative disc warps but instead by different feeding mechanisms with the majority consistent with coplanar accretion (although this may be the result of selection bias), whilst a smaller but not insignificant fraction may have been fuelled by minor mergers in the recent history of the host galaxy.

  20. Eddington ratios of faint AGN at intermediate redshift: evidence for a population of half-starved black holes

    NASA Astrophysics Data System (ADS)

    Gavignaud, I.; Wisotzki, L.; Bongiorno, A.; Paltani, S.; Zamorani, G.; Møller, P.; Le Brun, V.; Husemann, B.; Lamareille, F.; Schramm, M.; Le Fèvre, O.; Bottini, D.; Garilli, B.; Maccagni, D.; Scaramella, R.; Scodeggio, M.; Tresse, L.; Vettolani, G.; Zanichelli, A.; Adami, C.; Arnaboldi, M.; Arnouts, S.; Bardelli, S.; Bolzonella, M.; Cappi, A.; Charlot, S.; Ciliegi, P.; Contini, T.; Foucaud, S.; Franzetti, P.; Guzzo, L.; Ilbert, O.; Iovino, A.; McCracken, H. J.; Marano, B.; Marinoni, C.; Mazure, A.; Meneux, B.; Merighi, R.; Pellò, R.; Pollo, A.; Pozzetti, L.; Radovich, M.; Zucca, E.; Bondi, M.; Busarello, G.; Cucciati, O.; de La Torre, S.; Gregorini, L.; Mellier, Y.; Merluzzi, P.; Ripepi, V.; Rizzo, D.; Vergani, D.

    2008-12-01

    We use one of the deepest spectroscopic samples of broad-line active galactic nuclei (AGN) currently available, extracted from the VIMOS VLT Deep Survey (VVDS), to compute the Mg II and C IV virial-mass estimates of 120 super-massive black holes in the redshift range 1.0AGN luminosities (log L_bol ˜ 45). At these luminosities, there is a substantial fraction of black holes accreting far below their Eddington limit (L_bol/L_Edd < 0.1), in marked contrast to what is generally found for AGN of higher luminosities. We speculate that these may be AGN on the decaying branch of their lightcurves, well past their peak activity. This would agree with recent theoretical predictions of AGN evolution. In the electronic Appendix of this paper we publish an update of the VVDS type-1 AGN sample, including the first and most of the second-epoch observations. This sample contains 298 objects of which 168 are new. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, program 070.A-9007(A), 272.A-5047, 076.A-0808, and partially on data obtained at the Canada-France-Hawaii Telescope.

  1. X-Ray Absorbed, Broad-Lined, Red AGN and the Cosmic X-Ray Background

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Wilkes, Belinda

    2005-01-01

    We have obtained XMM spectra for five red, 2MASS AGN, selected from a sample observed by Chandra to be X-ray bright and to cover a range of hardness ratios. Our results confirm the presence of substantial absorbing material in three sources which have optical classifications ranging from Type 1 to Type 2, with an intrinsically flat (hard) power law continuum indicated in the other two. The presence of both X-ray absorption and broad optical emission lines with the usual strength suggests either a small (nuclear) absorber or a favored viewing angle so as to cover the X-ray source but not the broad emission line region (BELR). A soft excess is detected in all three Type 1 sources. We speculate that this soft X-ray emission may arise in an extended region of ionized gas, perhaps linked with the polarized (scattered) light which is a feature of these sources. The spectral complexity revealed by XMM emphasizes the limitations of the low S/N Chandra data. Overall, the new XMM results strengthen our conclusions (Wilkes et al. 2002) that the observed X-ray continua of red AGN are unusually hard at energies greater than 2 keV. Whether due to substantial line-of-sight absorption or to an intrinsically hard or reflection-dominated spectrum, these 'red' AGN have an observed spectral form consistent with contributing significantly to the missing had absorbed population of the Cosmic X-ray Background (CXRB). When absorption and or reflection is taken into account, all these AGN have power law slopes typical of broad-line (Type 1) AGN (Gamma approximately 1.9). This appears to resolve the spectral paradox which for so long has existed between the CXRB and the AGN thought to be the dominant contributors. It also suggests two scenarios whereby Type 1 AGN/QSOs may be responsible for a significant fraction of the CXRB at energies above 2 keV: 1) X-ray absorbed AGN/QSOs with visible broad emission lines; 2) AGN/QSOs with complex spectra whose hardness greater than 2 keV is not

  2. Cosmological, large-scale simulations of BH growth: demographics, the AGN-host connection and the relevance of mergers in driving nuclear activity

    NASA Astrophysics Data System (ADS)

    Hirschmann, Michaela; Dolag, Klaus; Bachmann, Lisa

    2015-08-01

    We provide new insights into the cosmic evolution of black holes (BHs) and their host galaxies by employing large-scale cosmological, hydrodynamic simulations capturing a huge volume of (500 Mpc)3. They are shown to be successful in reproducing a number of observational, statistical constraints, e.g. the evolution of the AGN luminosity function (in the soft and hard X-ray band) together with the corresponding downsizing trend. This is mainly due to the evolution of the gas density in the vicinity of a BH and due to the correction for dust obscuration on a torus-level. We further demonstrate that only luminous AGN are preferentially triggered by merger events, while for the majority of moderately luminous AGN, additional driving mechanisms seem to be necessary. Exploring the AGN-host connection, we find that host SFRs and AGN luminosities are always correlated (albeit with a large scatter) when averaging over the AGN luminosities (but not when averaging over SFR) in reasonably good agreement with recent observations. Interestingly, for the most luminous AGN, a slightly tighter and steeper correlation between AGN luminosities and SFRs emerges, which may originate from the increasing relevance of mergers in driving their nuclear activity. Overall, the new generation AGN, BH and galaxy catalogues, provided by our simulation, are expected to significantly contribute to the interpretation of current and up-coming large-scale surveys (XMM, ATHENA, eRosita, Euclid) with respect to the evolution of BHs within the emerging cosmic structure.

  3. The ROSAT/NVSS AGN sample

    NASA Astrophysics Data System (ADS)

    Paronyan, Gurgen M.; Abrahamyan, Hayk V.; Harutyunyan, Gohar S.; Mickaelian, Areg M.

    2014-07-01

    We attempt to create an X-ray/radio AGN catalog and make its multiwavelength studies. ROSAT Bright Source Catalogue (BSC) contains 18,806 and ROSAT Faint Source Catalogue (FSC), 105,922 X-ray sources giving the total number of ROSAT X-ray sources 124,727 (one source is listed twice). On the other hand, NVSS radio catalogue contains 1,773,484 sources. Taking into account that X-ray sources contain AGN, bright stars and galaxies, clusters, white dwarfs (WD), cataclysmic variables (CV), etc., the cross-identification with radio catalogue may distinguish the extragalactic sources. We have cross-correlated ROSAT catalogs with NVSS one with a search radius 30 arcsec. 9,193 associations have been found. To distinguish AGN from the normal bright galaxies and clusters, Veron-Cetty & Veron AGN catalog (v.13, 2010; VCV-13) containing 168,940 objects have been used. A cross-correlation of the 9,193 ROSAT/NVSS sources with the VCV-13 with a search radius 30 arcsec resulted in 3,094 associations. Thus we are left with more 6,099 X-ray/radio sources without an optical identification. Brighter objects are normal bright galaxies, while we believe that all faint ones are candidate AGN with some contamination of distant clusters. SDSS spectroscopic survey allows us classify objects by activity types, and a number of our candidate AGN is found to be present in SDSS. We attempt to find connections between the fluxes in different wavelength ranges, which will allow us to confirm AGN and blazars candidates and in some cases find new ones.

  4. Towards a paleo-salinity proxy: Decreasing D/H fractionation in algal and bacterial lipids with increasing salinity in Christmas Island saline ponds

    NASA Astrophysics Data System (ADS)

    Sachse, D.; Sachs, J. P.

    2007-12-01

    We investigated the effect of a wide range of salinities (13 -149 PSU) on the D/H ratio of lipids in microbial mat sediments from hypersaline ponds on Christmas Island. The hydrogen isotope ratios (expressed as δD values) of total lipid extracts, and the individual hydrocarbons heptadecane, heptadecene, octadecane, octadecene, diploptene and phytene from algae and bacteria, became increasingly enriched in deuterium as salinity increased, spanning a range of 100‰ while lake water δD values spanned a range of just 12‰. D/H fractionation between lipids and source water thus decreased as salinity increased. Isotope fractionation factors (αlipid-water) were strongly correlated with salinity and increased in all compound classes studied. The apparent isotope fractionation (ɛlipid-water) decreased by 0.8 to 1.1‰ per PSU increase in salinity. Differences in the hydrogen isotopic composition of lipids derived from three biosynthetic pathways (acetogenic, MVA and DOXP/MEP) remained similar irrespective of the salinity, suggesting that the mechanism responsible for the observed αlipid-water - salinity relationship originates prior to the last common biosynthetic branching point, the Calvin Cycle. These findings imply that caution must be exercised when attempting to reconstruct source water δD values using lipid δD values from aquatic environments that may have experienced salinity variations of ~3 PSU or more (based on a 1‰ per PSU response of D/H fractionation to salinity changes, and a lipid δD measurement precision of 3‰). On the other hand our results can be used to establish a paleo-salinity proxy based on algal and bacterial lipid δD values if salinity variations exceeded ~3 PSU and/or if additional constraints on source water δD values can be made.

  5. Reconfinement shocks in relativistic AGN jets

    SciTech Connect

    Nalewajko, Krzysztof; Sikora, Marek

    2008-12-24

    Stationary knots observed in many AGN jets can be explained in terms of a reconfinement shock that forms when relativistic flow of the jet matter collides with the external medium. The position of these knots can be used, together with information on external pressure profile, to constrain dynamical parameters of the jet. We present a semi-analytical model for the dynamical structure of reconfinement shocks, taking into account exact conservation laws both across the shock surface and in the zone of the shocked jet matter. We show that, due to the transverse pressure gradient in the shock zone, the position of the reconfinement is larger than predicted by simple models. A portion of kinetic energy is converted at the shock surface to internal energy, with efficiency increasing strongly with both bulk Lorentz factor of the jet matter and the jet half-opening angle. Our model may be useful as a framework for modeling non-thermal radiation produced within the stationary features.

  6. Compton-thick AGN in the 70-month Swift-BAT All-Sky Hard X-ray Survey: A Bayesian approach

    NASA Astrophysics Data System (ADS)

    Akylas, A.; Georgantopoulos, I.; Ranalli, P.; Gkiokas, E.; Corral, A.; Lanzuisi, G.

    2016-10-01

    The 70-month Swift-BAT catalogue provides a sensitive view of the extragalactic X-ray sky at hard energies (>10 keV) containing about 800 active galactic nuclei (AGN). We explore its content in heavily obscured, Compton-thick AGN by combining the BAT (14-195 keV) with the lower energy XRT (0.3-10 keV) data. We apply a Bayesian methodology using Markov chains to estimate the exact probability distribution of the column density for each source. We find 53 possible Compton-thick sources (probability range 3-100%) translating to a ~7% fraction of the AGN in our sample. We derive the first parametric luminosity function of Compton-thick AGN. The unabsorbed luminosity function can be represented by a double power law with a break at L⋆ ~ 2 × 1042erg s-1 in the 20-40 keV band. The Compton-thick AGN contribute ~17% of the total AGN emissivity. We derive an accurate Compton-thick number count distribution taking into account the exact probability of a source being Compton-thick and the flux uncertainties. This number count distribution is critical for the calibration of the X-ray background synthesis models, i.e. for constraining the intrinsic fraction of Compton-thick AGN. We find that the number counts distribution in the 14-195 keV band agrees well with our models which adopt a low intrinsic fraction of Compton-thick AGN (~ 12%) among the total AGN population and a reflected emission of ~ 5%. In the extreme case of zero reflection, the number counts can be modelled with a fraction of at most 30% Compton-thick AGN of the total AGN population and no reflection. Moreover, we compare our X-ray background synthesis models with the number counts in the softer 2-10 keV band. This band is more sensitive to the reflected component and thus helps us to break the degeneracy between the fraction of Compton-thick AGN and the reflection emission. The number counts in the 2-10 keV band are well above the models which assume a 30% Compton-thick AGN fraction and zero reflection, while

  7. Retired galaxies: not to be forgotten in the quest of the star formation - AGN connection

    NASA Astrophysics Data System (ADS)

    Stasińska, G.; Costa-Duarte, M. V.; Vale Asari, N.; Cid Fernandes, R.; Sodré, L.

    2015-05-01

    We propose a fresh look at the Main Galaxy Sample of the Sloan Digital Sky Survey by packing the galaxies in stellar mass and redshift bins. We show how important it is to consider the emission-line equivalent widths, in addition to the commonly used emission-line ratios, to properly identify retired galaxies (i.e. galaxies that have stopped forming stars and are ionized by their old stellar populations) and not mistake them for galaxies with low-level nuclear activity. We find that the proportion of star-forming galaxies decreases with decreasing redshift in each mass bin, while that of retired galaxies increases. Galaxies with M⋆ > 1011.5 M⊙ have formed all their stars at redshift larger than 0.4. The population of AGN hosts is never dominant for galaxy masses larger than 1010 M⊙. We warn about the effects of stacking galaxy spectra to discuss galaxy properties. We estimate the lifetimes of active galactic nuclei (AGN) relying entirely on demographic arguments - i.e. without any assumption on the AGN radiative properties. We find upper-limit lifetimes of about 1-5 Gyr for detectable AGN in galaxies with masses between 1010-1012 M⊙. The lifetimes of the AGN-dominated phases are a few 108 yr. Finally, we compare the star formation histories of star-forming, AGN and retired galaxies as obtained by the spectral synthesis code STARLIGHT. Once the AGN is turned on, it inhibits star formation for the next ˜0.1 Gyr in galaxies with masses around 1010 M⊙, ˜ 1 Gyr in galaxies with masses around 1011 M⊙.

  8. Ingestion of proteoglycan fraction from shark cartilage increases serum inhibitory activity against matrix metalloproteinase-9 and suppresses development of N-nitrosobis(2-oxopropyl)amine-induced pancreatic duct carcinogenesis in hamster.

    PubMed

    Kitahashi, Tsukasa; Ikawa, Shoko; Sakamoto, Akika; Nomura, Yoshihiro; Tsujiuchi, Toshifumi; Shimizu, Kenji; Sasabe, Shuji; Park, Eun Young; Nakamura, Yasushi; Tsutsumi, Masahiro; Sato, Kenji

    2012-02-01

    A water extract of shark cartilage was fractionated into acidic and basic fractions by preparative isoelectric focusing on the basis of the amphoteric nature of samples. The acidic fraction was further fractionated into ethanol-soluble and -precipitate fractions. After the carcinogenesis treatment using N-nitrosobis(2-oxopropyl)amine, hamsters received a diet containing each fraction or purified chondroichin sulfate to give 0.4% (w/w) for 50 days. Only administration of the acidic ethanol-precipitate-fraction-containing diet significantly increased serum inhibitory activity against matrix metalloproteinase (MMP)-9 and reduced the number of adenocarcinomas in the pancreatic duct. The active fraction predominantly consisted of chondroichin sulfate-containing proteoglycan. However, the purified chondroichin sulfate had no significant activity. These results suggest that the protein moiety of the proteoglycan might be involved in the increase of serum inhibitory activity against MMP-9 and suppression of pancreatic carcinogenesis in hamster.

  9. Steps Toward Unveiling the True Population of AGN: Photometric Selection of Broad-Line AGN

    NASA Astrophysics Data System (ADS)

    Schneider, Evan; Impey, C.

    2012-01-01

    We present an AGN selection technique that enables identification of broad-line AGN using only photometric data. An extension of infrared selection techniques, our method involves fitting a given spectral energy distribution with a model consisting of three physically motivated components: infrared power law emission, optical accretion disk emission, and host galaxy emission. Each component can be varied in intensity, and a reduced chi-square minimization routine is used to determine the optimum parameters for each object. Using this model, both broad- and narrow-line AGN are seen to fall within discrete ranges of parameter space that have plausible bounds, allowing physical trends with luminosity and redshift to be determined. Based on a fiducial sample of AGN from the catalog of Trump et al. (2009), we find the region occupied by broad-line AGN to be distinct from that of quiescent or star-bursting galaxies. Because this technique relies only on photometry, it will allow us to find AGN at fainter magnitudes than are accessible in spectroscopic surveys, and thus probe a population of less luminous and/or higher redshift objects. With the vast availability of photometric data in large surveys, this technique should have broad applicability and result in large samples that will complement X-ray AGN catalogs.

  10. Satellites of radio AGN in SDSS: Insights into agn triggering and feedback

    SciTech Connect

    Pace, Cameron; Salim, Samir E-mail: salims@indiana.edu

    2014-04-10

    We study the effects of radio jets on galaxies in their vicinity (satellites) and the role of satellites in triggering radio-loud active galactic nuclei (AGNs). The study compares the aggregate properties of satellites of a sample of 7220 radio AGNs at z < 0.3 (identified by Best and Heckman from the SDSS and NVSS+FIRST surveys) to the satellites of a control sample of radio-quiet galaxies, which are matched in redshift, color, luminosity, and axis ratio, as well as by environment type: field galaxies, cluster members, and brightest cluster galaxies (BCGs). Remarkably, we find that radio AGNs exhibit on average a 50% excess (17σ significance) in the number of satellites within 100 kpc even though the cluster membership was controlled (e.g., radio BCGs have more satellites than radio-quiet BCGs, etc.). Satellite excess is not confirmed for high-excitation sources, which are only 2% of radio AGN. Extra satellites may be responsible for raising the probability for hot gas AGN accretion via tidal effects or may otherwise enhance the intensity or duration of the radio-emitting phase. Furthermore, we find that the incidence of radio AGNs among potential hosts (massive ellipticals) is similar for field galaxies and for non-BCG cluster members, suggesting that AGN fueling depends primarily on conditions in the host halo rather than the parent, cluster halo. Regarding feedback, we find that radio AGNs, either high or low excitation, have no detectable effect on star formation in their satellites, as neither induced star formation nor star formation quenching is present in more than ∼1% of radio AGN.

  11. Satellites of Radio AGN in SDSS: Insights into AGN Triggering and Feedback

    NASA Astrophysics Data System (ADS)

    Pace, Cameron; Salim, Samir

    2014-04-01

    We study the effects of radio jets on galaxies in their vicinity (satellites) and the role of satellites in triggering radio-loud active galactic nuclei (AGNs). The study compares the aggregate properties of satellites of a sample of 7220 radio AGNs at z < 0.3 (identified by Best & Heckman from the SDSS and NVSS+FIRST surveys) to the satellites of a control sample of radio-quiet galaxies, which are matched in redshift, color, luminosity, and axis ratio, as well as by environment type: field galaxies, cluster members, and brightest cluster galaxies (BCGs). Remarkably, we find that radio AGNs exhibit on average a 50% excess (17σ significance) in the number of satellites within 100 kpc even though the cluster membership was controlled (e.g., radio BCGs have more satellites than radio-quiet BCGs, etc.). Satellite excess is not confirmed for high-excitation sources, which are only 2% of radio AGN. Extra satellites may be responsible for raising the probability for hot gas AGN accretion via tidal effects or may otherwise enhance the intensity or duration of the radio-emitting phase. Furthermore, we find that the incidence of radio AGNs among potential hosts (massive ellipticals) is similar for field galaxies and for non-BCG cluster members, suggesting that AGN fueling depends primarily on conditions in the host halo rather than the parent, cluster halo. Regarding feedback, we find that radio AGNs, either high or low excitation, have no detectable effect on star formation in their satellites, as neither induced star formation nor star formation quenching is present in more than ~1% of radio AGN.

  12. Reverberation Mapping of AGN Accretion Disks

    NASA Astrophysics Data System (ADS)

    Fausnaugh, Michael; AGN STORM Collaboration

    2017-01-01

    I will discuss new reverberation mapping results that allow us to investigate the temperature structure of AGN accretion disks. By measuring time-delays between broad-band continuum light curves, we can determine the size of the disk as a function of wavelength. I will discuss the detection of continuum lags in NGC 5548 reported by the AGN STORM project and implications for the accretion disk. I will also present evidence for continuum lags in two other AGN for which we recently measured black hole masses from continuum-Hbeta reverberations. The mass measurements allow us to compare the continuum lags to predictions from standard thin disk theory, and our results indicate that the accretion disks are larger than the simplest expectations.

  13. Observational evidence for thin AGN disks

    NASA Technical Reports Server (NTRS)

    Netzer, Hagai

    1992-01-01

    AGN spectrum and spectral features, polarization, inclination, and X-ray line and continuum reflection features are discussed in a critical way in order to determine the ones that are the least model-dependent. The sign and strength of absorption and emission edges are found to be model-dependent, and relativistic broadening and shifting makes them hard to detect. The presence or absence of the predicted Lyman edge polarization feature may be used as a decisive test for thin, bare AGN disks. Other good model-independent tests are several inclination-related line and continuum correlations in big AGN samples. It is shown that electron temperature near the surface of the disk can greatly exceed the disk equilibrium temperature, which causes deviations from LTE. This effect must be incorporated into realistic disk models.

  14. Probing AGN Accretion History Through X-Ray Variability

    NASA Astrophysics Data System (ADS)

    Paolillo, Maurizio; Papadakis, I.; Brandt, W. N.; Xue, Y. Q.; Luo, B.; Tozzi, P.; Shemmer, O.; Allevato, V.; Bauer, F.; Koekemoer, A.; Vignali, C.; Vito, F.; Yang, G.; Wang, J. X.; Zheng, X.

    2016-10-01

    I will present recent results on AGN variability in the CDFS survey. Using over 10 years of X-ray monitoring and comparison with local AGNs we are able to constrain the variability dependence on BH mass and accreton rate, and use it to trace the accretion hisory of the AGN population up to z=3.

  15. Compton Thick AGN in the 70 Month Swift-BAT All-Sky Hard X-ray Survey: a Bayesian approach

    NASA Astrophysics Data System (ADS)

    Georgantopoulos, I.; Akylas, A.; Ranalli, P.; Corral, A.; Lanzuisi, G.

    2016-08-01

    The 70 month Swift/BAT catalogue provides a sensitive view of the extragalactic X-ray sky at hard energies 14-195 keV containing about 800 Active Galactic Nuclei. We explore its content in heavily obscured Compton-thick AGN by combining the BAT (14-195 keV) with the XRT data (0.3-10 keV) at lower energies. We apply a Bayesian methodology using Markov chains to estimate the exact probability distribution of the column density. We find 54 possible Compton-thick sources (from 3 to 100 % probability) translating to a 7% fraction of the total AGN population. We derive an accurate Compton-thick number count distribution taking into account the exact probability of a source being Compton-thick as well as the flux errors. The number density of Compton-thick AGN is critical for the calibration of X-ray background synthesis models. We find that the number count distribution agrees with models that adopt a low intrinsic fraction of Compton-thick AGN (15%) among the total AGN population and a reflected emission of (~5%). Finally, we derive the first parametric luminosity function of Compton-thick AGN in the local universe. The unabsorbed luminosity function can be represented by a double power-law with a break at L* ~2 x 10^42 ergs in the 20-40 keV band. The Compton-thick AGN constitute a substantial fraction of the AGN density at low luminosities (<10^42 erg/s).

  16. Modeling optical and UV polarization of AGNs. III. From uniform-density to clumpy regions

    NASA Astrophysics Data System (ADS)

    Marin, F.; Goosmann, R. W.; Gaskell, C. M.

    2015-05-01

    Context. A growing body of evidence suggests that some, if not all, scattering regions of active galactic nuclei (AGNs) are clumpy. The inner AGN components cannot be spatially resolved with current instruments and must be studied by numerical simulations of observed spectroscopy and polarization data. Aims: We run radiative transfer models in the optical/UV for a variety of AGN reprocessing regions with different distributions of clumpy scattering media. We obtain geometry-sensitive polarization spectra and images to improve our previous AGN models and their comparison with the observations. Methods: We use the latest public version 1.2 of the Monte Carlo code stokes presented in the first two papers of this series to model AGN reprocessing regions of increasing morphological complexity. We replace previously uniform-density media with up to thousands of constant-density clumps. We couple a continuum source to fragmented equatorial scattering regions, polar outflows, and toroidal obscuring dust regions and investigate a wide range of geometries. We also consider different levels of fragmentation in each scattering region to evaluate the importance of fragmentation for the net polarization of the AGN. Results: In comparison with uniform-density models, equatorial distributions of gas and dust clouds result in grayer spectra and show a decrease in the net polarization percentage at all lines of sight. The resulting polarization position angle depends on the morphology of the clumpy structure, with extended tori favoring parallel polarization while compact tori produce orthogonal polarization position angles. In the case of polar scattering regions, fragmentation increases the net polarization unless the cloud filling factor is small. A complete AGN model constructed from the individual, fragmented regions can produce low polarization percentages (<2%), with a parallel polarization angle for observer inclinations up to 70° for a torus half opening angle of 60°. For

  17. Complete Hard X-Ray Surveys, AGN Luminosity Functions and the X-Ray Background

    NASA Technical Reports Server (NTRS)

    Tueller, Jack

    2011-01-01

    AGN are believed to make up most of the Cosmic X-Ray Background (CXB) above a few keV, but this background cannot be fully resolved at energies less than 10 keV due to absorption. The Swift/BAT and INTEGRAL missions are performing the first complete hard x-ray surveys with minimal bias due to absorption. The most recent results for both missions will be presented. Although the fraction of the CXB resolved by these surveys is small, it is possible to derive unbiased number counts and luminosity functions for AGN in the local universe. The survey energy range from 15-150 keV contains the important reflection and cutoff spectral features dominate the shape of the AGN contribution to the CXB. Average spectral characteristics of survey detected AGN will be presented and compared with model distributions. The numbers of hard x-ray blazars detected in these surveys are finally sufficient to estimate this important component's contribution the cosmic background. Constraints on CXB models and their significance will be discussed.

  18. Au13-nAgn clusters: a remarkably simple trend.

    PubMed

    Munoz, Francisco; Varas, Alejandro; Rogan, José; Valdivia, Juan Alejandro; Kiwi, Miguel

    2015-11-11

    The planar to three dimensional transition of Au13-nAgn clusters is investigated. To do so the low lying energy configurations for all possible concentrations (n values) are evaluated. Many thousands of possible conformations are examined. They are generated using the procedure developed by Rogan et al. in combination with the semi-empirical Gupta potential. A large fraction of these (the low lying energy ones) are minimized by means of Density Functional Theory (DFT) calculations. We employ the Tao, Perdew, Staroverov, and Scuseria (TPSS) meta-GGA functional and the Perdew, Burke and Ernzerhof (PBE) GGA functional, and compare their results. The effect of spin-orbit coupling is studied as well as the s-d hybridization. As usual in this context the results are functional-dependent. However, both functionals lead to agreement as far as trends are concerned, yielding just two relevant motifs, but their results differ quantitatively.

  19. AGN Host Galaxy Properties And Mass Function

    NASA Astrophysics Data System (ADS)

    Bongiorno, Angela

    2016-10-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z˜2.5, with particular focus on AGN feedback as possible responsible mechanism for galaxy quenching.

  20. PS1-1000305 an AGN outburst?

    NASA Astrophysics Data System (ADS)

    Drake, A. J.; Mahabal, A. A.; Djorgovski, S. G.; Graham, M. J.; Williams, R.; Prieto, J.; Catelan, M.; Christensen, E.; Beshore, E. C.; Larson, S. M.

    2010-07-01

    Kankare et al. (2010, ATel#2716) recently reported the discovery of an AGN outburst (PS1-1000305) detected in PS1 taken data on May 19.3 UT. The redshift of the AGN is given by Kankare et al. as z=0.77 with the host galaxy SDSS J152844.16+425722.5. We have extracted the five year archival CSS/CRTS lightcurve at the location of PS1-1000305.

  1. Multi-Frequency View Of Jetted AGN

    NASA Astrophysics Data System (ADS)

    Giroletti, Marcello; Orienti, M.; D'Ammando, F.; Lico, R.; Giovannini, G.:

    2016-10-01

    I will present a review on the context and the most recent results about radio loud AGNs as seen in different parts of the electromagnetic spectrum, with an eye also to multi-messenger astrophysics and neutrinos in particular. I will focus on various topics of interest about RL AGNs, such as: the study of the physics of relativistic jets and particle acceleration, in particular through VLBI and gamma ray observations; the feedback to the host galaxy and on galaxy cluster scales; the possibility to probe distant and obscured environments.

  2. Discovery of a population of bulgeless galaxies with extremely red MID-IR colors: Obscured AGN activity in the low-mass regime?

    SciTech Connect

    Satyapal, S.; Secrest, N. J.; McAlpine, W.; Rosenberg, J. L.; Ellison, S. L.; Fischer, J.

    2014-04-01

    In contrast to massive, bulge hosting galaxies, very few supermassive black holes (SMBHs) are known in either low-mass or bulgeless galaxies. Such a population could provide clues to the origins of SMBHs and to secular pathways for their growth. Using the all-sky Wide-field Infrared Survey Explorer (WISE ) survey, and bulge-to-disk decompositions from the Sloan Digital Sky Survey (SDSS) Data Release 7, we report the discovery of a population of local (z < 0.3) bulgeless disk galaxies with extremely red mid-infrared colors which are highly suggestive of a dominant active galactic nucleus (AGN), despite having no optical AGN signatures in their SDSS spectra. Using various mid-infrared selection criteria from the literature, there are between 30 and over 300 bulgeless galaxies with possible AGNs. Other known scenarios that can heat the dust to high temperatures do not appear to explain the observed colors of this sample. If these galaxies are confirmed to host AGNs, this study will provide a breakthrough in characterizing the properties of SMBHs in the low bulge mass regime and in understanding their relation with their host galaxies. Mid-infrared selection identifies AGNs that dominate their host galaxy's emission and therefore reveal a different AGN population than that uncovered by optical studies. We find that the fraction of all galaxies identified as candidate AGNs by WISE is highest at lower stellar masses and drops dramatically in higher mass galaxies, in striking contrast to the findings from optical studies.

  3. Probing the Black Hole-Galaxy Connection with AGN Host Galaxy Morphologies

    NASA Astrophysics Data System (ADS)

    Simmons, Brooke; Urry, C. M.; COSMOS Team

    2006-12-01

    There is increasing evidence that galaxies and supermassive black holes form and evolve together, exerting mutual feedback that governs the galaxy dynamics and the black hole mass. During their growth phase, supermassive black holes are readily visible as Active Galactic Nuclei (AGN). The morphologies of AGN host galaxies offer a powerful, direct probe of the AGN-galaxy connection. We are carrying out morphological analysis of large AGN samples from deep multi-wavelength surveys, comparing the results to well-selected samples of inactive galaxies. To interpret the results properly requires understanding the observational bias introduced by the central point source, which can hide compact features and thus influence the extracted AGN host morphological parameters. Therefore, we performed extensive simulations, involving a variety of galaxy types over a range of redshifts. Here we present results of these simulations and describe preliminary work on deep HST ACS images from the COSMOS field. We gratefully acknowledge support from HST grants AR-10689.01-A and GO-09822.09-A, and Yale University.

  4. Probing the Black Hole-Galaxy Connection with AGN Host Galaxy Morphologies

    NASA Astrophysics Data System (ADS)

    Simmons, Brooke; Urry, C. M.; COSMOS Team

    2007-05-01

    There is increasing evidence that galaxies and supermassive black holes form and evolve together, exerting mutual feedback that governs the galaxy dynamics and the black hole mass. During their growth phase, supermassive black holes are readily visible as Active Galactic Nuclei (AGN). The morphologies of AGN host galaxies offer a powerful, direct probe of the AGN-galaxy connection. We are carrying out morphological analysis of large AGN samples from deep multi-wavelength surveys, comparing the results to well-selected samples of inactive galaxies. To interpret the results properly requires understanding the observational bias introduced by the central point source, which can hide compact features and thus influence the extracted AGN host morphological parameters. Therefore, we performed extensive simulations, involving a variety of galaxy types over a range of redshifts. Here we present results of these simulations and describe preliminary work on deep HST ACS images from the COSMOS field. We gratefully acknowledge support from HST grants AR-10689.01-A and GO-09822.09-A, and Yale University.

  5. The VIMOS Ultra-Deep Survey (VUDS): fast increase in the fraction of strong Lyman-α emitters from z = 2 to z = 6

    NASA Astrophysics Data System (ADS)

    Cassata, P.; Tasca, L. A. M.; Le Fèvre, O.; Lemaux, B. C.; Garilli, B.; Le Brun, V.; Maccagni, D.; Pentericci, L.; Thomas, R.; Vanzella, E.; Zamorani, G.; Zucca, E.; Amorin, R.; Bardelli, S.; Capak, P.; Cassarà, L. P.; Castellano, M.; Cimatti, A.; Cuby, J. G.; Cucciati, O.; de la Torre, S.; Durkalec, A.; Fontana, A.; Giavalisco, M.; Grazian, A.; Hathi, N. P.; Ilbert, O.; Moreau, C.; Paltani, S.; Ribeiro, B.; Salvato, M.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Taniguchi, Y.; Tresse, L.; Vergani, D.; Wang, P. W.; Charlot, S.; Contini, T.; Fotopoulou, S.; Koekemoer, A. M.; López-Sanjuan, C.; Mellier, Y.; Scoville, N.

    2015-01-01

    Aims: The aim of this work is to constrain the evolution of the fraction of strong Lyα emitters among UV selected star-forming galaxies at 2 fraction of Lyα photons over the same redshift range. Methods: We exploit the ultradeep spectroscopic observations with VIMOS on the VLT collected by the VIMOS Ultra-Deep Survey (VUDS) to build an unique, complete, and unbiased sample of ~4000 spectroscopically confirmed star-forming galaxies at 2 increases, and causes the fraction of strong Lyα with EW0(Lyα) > 25 Å to increase from ~5% at z ~ 2 to ~30% at z ~ 6, with the increase being stronger beyond z ~ 4. We observe no difference, for the narrow range of UV luminosities explored in this work, between the fraction of strong Lyα emitters among galaxies fainter or brighter than M*FUV, although the fraction for the faint galaxies evolves faster, at 2

  6. On the Star Formation-AGN Connection at zeta (is) approximately greater than 0.3

    NASA Technical Reports Server (NTRS)

    LaMassa, Stephanie M.; Heckman, T. M.; Ptak, Andrew; Urry, C. Megan

    2013-01-01

    Using the spectra of a sample of approximately 28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between active galactic nucleus (AGN) activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [O iii] 5007A line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3 inch SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formation is associated with AGN activity, and that it increasingly dominates over omnipresent disk star formation at higher AGN luminosities, placing critical constraints on theoretical models that link host galaxy star formation and SMBH fueling. We parameterize this relationship and find that the star formation on radial scales (is) less than 1.7 kpc, when including a constant disk component, has a sub-linear dependence on SMBH accretion rate: SFR in proportion to solar mass(sup 0.36), suggesting that angular momentum transfer through the disk limits accretion efficiency rather than the supply from stellar mass loss.

  7. ON THE STAR FORMATION-AGN CONNECTION AT z {approx}< 0.3

    SciTech Connect

    LaMassa, Stephanie M.; Urry, C. Megan; Heckman, T. M.; Ptak, A.

    2013-03-10

    Using the spectra of a sample of {approx}28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between active galactic nucleus (AGN) activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [O III] 5007 A line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3'' SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formation is associated with AGN activity, and that it increasingly dominates over omnipresent disk star formation at higher AGN luminosities, placing critical constraints on theoretical models that link host galaxy star formation and SMBH fueling. We parameterize this relationship and find that the star formation on radial scales <1.7 kpc, when including a constant disk component, has a sub-linear dependence on SMBH accretion rate: SFR{proportional_to} M-dot {sup 0.36}, suggesting that angular momentum transfer through the disk limits accretion efficiency rather than the supply from stellar mass loss.

  8. Star Formation and AGN activity of X-ray selected AGN host galaxies in the Chandra-COSMOS Legacy Survey

    NASA Astrophysics Data System (ADS)

    Suh, Hyewon

    2017-01-01

    One of the ongoing issues for understanding the galaxy formation and evolution is how active galactic nuclei (AGNs) affect the growth of their host galaxies. We investigate the correlations between AGN activity and star formation properties of a large sample of ~3700 X-ray selected AGNs over a wide range of luminosities (42 < log Lx < 45) up to z~5 in the Chandra-COSMOS Legacy Survey. We perform a multi-component modeling from the far-infrared, when available, to the near-UV using AGN emission from the big-blue-bump (for Type 1 AGNs), a nuclear dust torus model, a galaxy model and a starburst component for the spectral energy distributions (SEDs). Through detailed analysis of SEDs, we derive AGN host galaxy properties, such as stellar masses, star formation rates (SFRs), and AGN luminosities. We find that AGN host galaxies have, on average, similar SFRs compared to the normal star-forming main sequence galaxies, suggesting no significant enhancement or quenching of star formation. The average SFR of AGN host galaxies shows a flat distribution in bins of AGN luminosity, consistent with recent ideas that the shorter variability timescale of AGN compared to star formation can lead to a flat relationship between the SFR and black hole accretion rates. Our results suggest that both star formation and nuclear activity in the majority of AGN host galaxies might be driven more by internal secular processes at z<3, implying that they have substantially grown at much earlier epoch.

  9. The spatial distribution of X-ray selected AGN in the Chandra deep fields: a theoretical perspective

    NASA Astrophysics Data System (ADS)

    Marulli, Federico; Bonoli, Silvia; Branchini, Enzo; Gilli, Roberto; Moscardini, Lauro; Springel, Volker

    2009-07-01

    We study the spatial distribution of X-ray selected active galactic nuclei (AGN) in the framework of hierarchical coevolution of supermassive black holes and their host galaxies and dark matter haloes. To this end, we have applied the theoretical model developed by Croton et al., De Lucia & Blaizot and Marulli et al. to the output of the Millennium Run and obtained hundreds of realizations of past light cones from which we have extracted realistic mock AGN catalogues that mimic the Chandra deep fields. We find that the model AGN number counts are in fair agreement with observations both in the soft and in the hard X-ray bands, except at fluxes <~10-15ergcm-2s-1, where the model systematically overestimates the observations. However, a large fraction of these faint objects are typically excluded from the spectroscopic AGN samples of the Chandra fields. We find that the spatial two-point correlation function predicted by the model is well described by a power-law relation out to 20h-1Mpc, in close agreement with observations. Our model matches the correlation length r0 of AGN in the Chandra Deep Field-North but underestimates it in the Chandra Deep Field-South. When fixing the slope to γ = 1.4, as in Gilli et al., the statistical significance of the mismatch is 2σ-2.5σ, suggesting that the predicted cosmic variance, which dominates the error budget, may not account for the different correlation length of the AGN in the two fields. However, the overall mismatch between the model and the observed correlation function decreases when both r0 and γ are allowed to vary, suggesting that more realistic AGN models and a full account of all observational errors may significantly reduce the tension between AGN clustering in the two fields. While our results are robust to changes in the model prescriptions for the AGN light curves, the luminosity dependence of the clustering is sensitive to the different light-curve models adopted. However, irrespective of the model

  10. Radio AGN in 13,240 galaxy clusters from the Sloan Digital Sky Survey

    SciTech Connect

    Croft, S; de Vries, W; Becker, R

    2007-05-30

    We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 {le} z {le} 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of our BCGs are radio-loud, and this fraction depends on the stellar mass of the BCG, and to a lesser extent on the richness of the parent cluster (in the sense of increasing radio loudness with increasing mass). The intrinsic size of the radio emission associated with the BCGs peaks at 55 kpc, with a tail extending to 200 kpc. The radio power of the extended sources places them on the divide between FR I and FR II type sources, while sources compact in the radio tend to be somewhat less radio-luminous. We also detect an excess of radio sources associated with the cluster, instead of with the BCG itself, extending out to {approx} 1.4 kpc.

  11. Application of acetyl-CoA acetyltransferase (AtoAD) in Escherichia coli to increase 3-hydroxyvalerate fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

    PubMed

    Jeon, Jong-Min; Kim, Hyun-Joong; Bhatia, Shashi Kant; Sung, Changmin; Seo, Hyung-Min; Kim, Jung-Ho; Park, Hyung-Yeon; Lee, Dahye; Brigham, Christopher J; Yang, Yung-Hun

    2017-02-16

    Polyhydroxyalkanoate (PHA) is a family of biodegradable polymers, and incorporation of different monomers can alter its physical properties. To produce the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) containing a high level of 3-hydroxyvalerate (3HV) by altering acetyl-CoA pool levels, we overexpressed an acetyl-CoA acetyltransferase (atoAD) in an engineered E. coli strain, YH090, carrying PHA synthetic genes bktB, phaB, and phaC. It was found that, with introduction of atoAD and with propionate as a co-substrate, 3HV fraction in PHA was increased up to 7.3-fold higher than a strain without atoAD expressed in trans (67.9 mol%). By the analysis of CoA pool concentrations in vivo and in vitro using HPLC and LC-MS, overexpression of AtoAD was shown to decrease the amount of acetyl-CoA and increase the propionyl-CoA/acetyl-CoA ratio, ultimately resulting in an increased 3HV fraction in PHA. Finally, synthesis of P(3HB-co-3HV) containing 57.9 mol% of 3HV was achieved by fed-batch fermentation of YJ101 with propionate.

  12. The HORIZON-AGN simulation: morphological diversity of galaxies promoted by AGN feedback

    NASA Astrophysics Data System (ADS)

    Dubois, Yohan; Peirani, Sébastien; Pichon, Christophe; Devriendt, Julien; Gavazzi, Raphaël; Welker, Charlotte; Volonteri, Marta

    2016-12-01

    The interplay between cosmic gas accretion on to galaxies and galaxy mergers drives the observed morphological diversity of galaxies. By comparing the state-of-the-art hydrodynamical cosmological simulations HORIZON-AGN and HORIZON-NOAGN, we unambiguously identify the critical role of active galactic nuclei (AGN) in setting up the correct galaxy morphology for the massive end of the population. With AGN feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. Only AGN feedback allows massive galaxies at the centre of groups and clusters to become ellipticals, while without AGN feedback those galaxies reform discs. It is the merger-enhanced AGN activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. Hence morphology is shown to be driven not only by mass but also by the nature of cosmic accretion: at constant galaxy mass, ellipticals are galaxies that are mainly assembled through mergers, while discs are preferentially built from the in situ star formation fed by smooth cosmic gas infall.

  13. A Global Picture of AGN Winds

    NASA Technical Reports Server (NTRS)

    Kazanas, D.; Fukumura, K.

    2011-01-01

    We present a unified structure for accretion powered sources across their entire luminosity range from accreting galactic black holes to the most luminous quasars, with emphasis on AGN and their phenomenology. Central to this end is the notion of MHD winds launched from the accretion disks that power these objects. This work similar in spirit to that of Elvis of more that a decade ago, provides, on one hand, only the broadest characteristics of these objects, but on the other, also scaling laws that allow one to make contact with objects of different luminosity. The conclusion of this work is that AGN phenomenology can be accounted for in terms of dot(m), the wind mass flux in units of the Eddington value, the observer's inclination angle theta and alpha_OX the logarithmic slope between UV and X-ray flares. However given the well known correlation between alpha(sub ox) and UV Luminosity, we conclude that the AGN structure depends on only two parameters. The small number of model parameters hence suggests that an understanding of the global AGN properties maybe within reach.

  14. NuSTAR Observations of Bright AGNs

    NASA Astrophysics Data System (ADS)

    Elvis, Martin; Ballantyne, D. R.; Blandford, R. D.; Boggs, S.; Boydstun, K.; Brenneman, L.; Cappi, M.; Christensen, F.; Craig, W.; Fabian, A.; Fuerst, F.; Guainazzi, M.; Hailey, C. J.; Harrison, F.; Madejski, G. M.; Marinucci, A.; Matt, G.; Nandra, K.; Reynolds, C. S.; Stern, D.; Walton, D.; Zhang, W.; NuSTAR Team

    2013-01-01

    The dramatically improved signal-to-noise provided by NuSTAR up to ~80 keV allows a qualitative change in our understanding of the X-ray emission of Active Galactic Nuclei (AGNs). Despite intensive investigation for over 30 years, during which the 0.1-10 keV spectra and variability of AGNs have been mapped out in detail, we do not know the origin of the X-ray source in AGNs. The "standard model" of supermassive black hole, accretion disk and relativistic jet does not predict an X-ray source in a straightforward way. It is usually assumed that the X-rays were UV photons from the accretion disk that have been Compton up-scattered in a "hot corona", but the temperature, optical depth and geometry of this corona are unknown - if it exists. NuSTAR enables the measurement of the high energy cut-off of the X-ray spectrum, and so the corona temperature, to be measured precisely for the first time, and tests the relativistic Fe-K line and Compton reflection models. If this model is correct then, with Suzaku and XMM-Newton, NuSTAR can measure black hole spins to high accuracy. We outline the NuSTAR GTO program on bright, unobscured, AGNs including simultaneous observations with Suzaku and XMM-Newton, and show early data.

  15. Mabel Agnes Elliott, We Hardly Knew You

    ERIC Educational Resources Information Center

    McGonigal, Kathryn; Galliher, John F.

    2008-01-01

    Sociologist Mabel Agnes Elliott was elected the fourth president of the Society for the Study of Social Problems in 1956-1957 and was the first woman to hold this position. She was an anti-war activist, a feminist and a creative and diligent writer. Yet she experienced many challenges. The Federal Bureau of Investigation kept an active file on…

  16. What are the galaxies that host MIR-selected AGN?

    NASA Astrophysics Data System (ADS)

    Rosario, David

    2016-08-01

    Infra-red selection techniques, sensitive to dust strongly heated by an AGN, offer a way to identify some of the most obscured accretion events in the Universe. I will describe the results of a comprehensive multi-wavelength study of AGN to z>2 selected using Spitzer/IRAC based methods in the COSMOS field. Armed with AGN-optimised redshifts and stellar masses, we explore the dust emission from the active nucleus and the host galaxy. We demonstrate that IR-selected AGN tend to be found in low mass host galaxies, when compared to other AGN identification methods. The star-formation rates of obscured and unobscured IR-selected AGN are very similar, implying that large-scale obscuration with co-eval star-bursts are not found in a major proportion of heavily obscured AGN.

  17. Effects on the optical properties and conductivity of Ag-N co-doped ZnO

    NASA Astrophysics Data System (ADS)

    Xu, Zhenchao; Hou, Qingyu; Qu, Lingfeng

    2017-01-01

    Nowadays, the studies of the effects on the optical bandgap, absorption spectrum, and electrical properties of Ag-N co-doped ZnO have been extensively investigated. However, Ag and N atoms in doped systems are randomly doped, and the asymmetric structure of ZnO is yet to be explored. In this paper, the geometric structure, stability, density of states, absorption spectra and conductivity of pure and Ag-N co-doped Zn1‑xAgxO1‑xNx(x=0.03125, 0.0417 and 0.0625) in different orientations are calculated by using plane-wave ultrasoft pseudopotential on the basis of density functional theory with GGA+U method. Results show that the volume, equivalent total energy and formation energy of the doped system increase as the concentration of Ag-N co-doped Zn1‑xAgxO1‑xNx increases at the same doping mode. The doped systems also become unstable, and difficulty in doping. At the same concentration of Ag-N co-doped Zn1‑xAgxO1‑xNx, the systems with Ag-N along the c-axis orientation is unstable, and doping is difficult. The optical bandgap of Ag-N co-doped systems is narrower than that of the pure ZnO. At the same doping mode, the optical bandgap of the systems with Ag-N perpendicular to the c-axis orientation becomes narrow as the concentration of Ag-N co-doped Zn1‑xAgxO1‑xNx increases. The absorption spectra of the doped systems exhibit a red shift, and this red shift becomes increasingly significant as the concentration of Ag-N co-doped Zn1‑xAgxO1‑xNx increases. Under the same condition, the relative hole concentrations of the doped systems increases, the hole effective mass in valence band maximum decreases, the hole mobility decreases, the ionization energy decreases, Bohr radius increases, the conductance increases and the conductivity become better. Our results may be used as a basis for the designing and preparation of new optical and electrical materials for Ag-N co-doped ZnO applied in low temperature end of temperature difference battery.

  18. AGN-host galaxy connection: multiwavelength study

    NASA Astrophysics Data System (ADS)

    Pović, M.; Sánchez-Portal, M.; García, A. M. Pérez; Bongiovanni, A.; Cepa, J.; Cepa

    2013-02-01

    The connection between active galactic nuclei (AGN) and their hosts showed to be important for understanding the formation and evolution of active galaxies. Using X-ray and deep optical data, we study how morphology and colours are related to X-ray properties at redshifts z<=2.0 for a sample of > 300 X-ray detected AGN in the Subaru/XMM-Newton Deep Survey (SXDS; Furusawa et al. 2008) and Groth-Westphal Strip (GWS; Pović et al. 2009) fields. We performed our morphological classification using the galSVM code (Huertas-Company et al. 2008), which is a new method that is particularly suited when dealing with high-redshift sources. To separate objects between X-ray unobscured and obscured, we used X-ray hardness ratio HR(0.5-2 keV/2-4.5 keV). Colour-magnitude diagrams were studied in relationship to redshift, morphology, X-ray obscuration, and X-ray-to-optical flux ratio. Around 50% of X-ray detected AGN at z<=2.0 analysed in this work reside in spheroidal and bulge-dominated galaxies, while at least 18% have disk-dominated hosts. This suggests that different mechanisms may be responsible for triggering the nuclear activity. When analysing populations of X-ray detected AGN in both colour-magnitude (CMD) and colour-stellar mass diagrams (Figure 1), the highest number of sources is found to reside in the green valley at redshifts ~ 0.5-1.5. For the first time we studied CMD of these AGN in relation to morphology and X-ray obscuration, finding that they can reside in both early- and late-type hosts, where both morphological types cover similar ranges of X-ray obscuration (Figure 1). Our findings appear to confirm some previous suggestions that X-ray selected AGN residing in the green valley represent a transitional population (e.g. Nandra et al. 2007, Silverman et al. 2008, Treister et al. 2009), quenching star formation by means of different AGN feedback mechanisms and evolving to red-sequence galaxies. More details on analysis and results presented here can be found in

  19. Long-term combined chemical and manure fertilizations increase soil organic carbon and total nitrogen in aggregate fractions at three typical cropland soils in China.

    PubMed

    He, Y T; Zhang, W J; Xu, M G; Tong, X G; Sun, F X; Wang, J Z; Huang, S M; Zhu, P; He, X H

    2015-11-01

    Soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) and nitrogen (MBN) are important factors of soil fertility. However, effects of the combined chemical fertilizer and organic manure or straw on these factors and their relationships are less addressed under long-term fertilizations. This study addressed changes in SOC, TN, MBC and MBN at 0-20 cm soil depth under three 17 years (September 1990-September 2007) long-term fertilization croplands along a heat and water gradient in China. Four soil physical fractions (coarse free and fine free particulate organic C, cfPOC and ffPOC; intra-microaggregate POC, iPOC; and mineral associated organic C, MOC) were examined under five fertilizations: unfertilized control, chemical nitrogen (N), phosphorus (P) and potassium (K) (NPK), NPK plus straw (NPKS, hereafter straw return), and NPK plus manure (NPKM and 1.5NPKM, hereafter manure). Compared with Control, manure significantly increased all tested parameters. SOC and TN in fractions distributed as MOC > iPOC > cfPOC > ffPOC with the highest increase in cfPOC (329.3%) and cfPTN (431.1%), and the lowest in MOC (40.8%) and MTN (45.4%) under manure. SOC significantly positively correlated with MBC, cfPOC, ffPOC, iPOC and MOC (R(2) = 0.51-0.84, P < 0.01), while TN with cfPTN, ffPTN, iPTN and MTN (R(2) = 0.45-0.79, P < 0.01), but not with MBN, respectively. Principal component analyses explained 86.9-91.2% variance of SOC, TN, MBC, MBN, SOC and TN in each fraction. Our results demonstrated that cfPOC was a sensitive SOC indicator and manure addition was the best fertilization for improving soil fertility while straw return should take into account climate factors in Chinese croplands.

  20. A POWERFUL AGN OUTBURST IN RBS 797

    SciTech Connect

    Cavagnolo, K. W.; McNamara, B. R.; Wise, M. W.; Nulsen, P. E. J.; Gitti, M.; Brueggen, M.; Rafferty, D. A.

    2011-05-10

    Utilizing {approx}50 ks of Chandra X-Ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements of the two cavities are unusually large and are consistent with elongated cavities lying close to our line of sight. We estimate a total AGN outburst energy and mean jet power of {approx}(3-6) x 10{sup 60} erg and {approx}(3-6) x 10{sup 45} erg s{sup -1}, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is {approx}1 M{sub sun} yr{sup -1}. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of {approx}2 x 10{sup 44} erg s{sup -1}. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be driving weak shocks (M {approx} 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.

  1. AGN Variability: Probing Black Hole Accretion

    NASA Astrophysics Data System (ADS)

    Moreno, Jackeline; O'Brien, Jack; Vogeley, Michael S.; Richards, Gordon T.; Kasliwal, Vishal P.

    2017-01-01

    We combine the long temporal baseline of Sloan Digital Sky Survey (SDSS) for quasars in Stripe 82 with the high precision photometry of the Kepler/K2 Satellite to study the physics of optical variability in the accretion disk and supermassive black hole engine. We model the lightcurves directly as Continuous-time Auto Regressive Moving Average processes (C-ARMA) with the Kali analysis package (Kasliwal et al. 2016). These models are extremely robust to irregular sampling and can capture aperiodic variability structure on various timescales. We also estimate the power spectral density and structure function of both the model family and the data. A Green's function kernel may also be estimated for the resulting C-ARMA parameter fit, which may be interpreted as the response to driving impulses such as hotspots in the accretion disk. We also examine available spectra for our AGN sample to relate observed and modelled behavior to spectral properties. The objective of this work is twofold: to explore the proper physical interpretation of different families of C-ARMA models applied to AGN optical flux variability and to relate empirical characteristic timescales of our AGN sample to physical theory or to properties estimated from spectra or simulations like the disk viscosity and temperature. We find that AGN with strong variability features on timescales resolved by K2 are well modelled by a low order C-ARMA family while K2 lightcurves with weak amplitude variability are dominated by outliers and measurement errors which force higher order model fits. This work explores a novel approach to combining SDSS and K2 data sets and presents recovered characteristic timescales of AGN variability.

  2. X-ray and Ultraviolet Properties of AGNs in Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

    2017-02-01

    We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies (z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad Hα emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad Hα and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L 0.5–7keV ≈ 5 × 1039 to 1 × 1042 ergs‑1. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ∼7 × 104 to 1 × 106 M ⊙), we find inferred Eddington fractions ranging from ∼0.1% to 50%, i.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e., α OX values an average of 0.36 lower than expected based on the relation between α OX and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.

  3. A silk peptide fraction restores cognitive function in AF64A-induced Alzheimer disease model rats by increasing expression of choline acetyltransferase gene.

    PubMed

    Cha, Yeseul; Lee, Sang Hoon; Jang, Su Kil; Guo, Haiyu; Ban, Young-Hwan; Park, Dongsun; Jang, Gwi Yeong; Yeon, Sungho; Lee, Jeong-Yong; Choi, Ehn-Kyoung; Joo, Seong Soo; Jeong, Heon-Sang; Kim, Yun-Bae

    2017-01-01

    This study investigated the effects of a silk peptide fraction obtained by incubating silk proteins with Protease N and Neutrase (SP-NN) on cognitive dysfunction of Alzheimer disease model rats. In order to elucidate underlying mechanisms, the effect of SP-NN on the expression of choline acetyltransferase (ChAT) mRNA was assessed in F3.ChAT neural stem cells and Neuro2a neuroblastoma cells; active amino acid sequence was identified using HPLC-MS. The expression of ChAT mRNA in F3.ChAT cells increased by 3.79-fold of the control level by treatment with SP-NN fraction. The active peptide in SP-NN was identified as tyrosine-glycine with 238.1 of molecular weight. Male rats were orally administered with SP-NN (50 or 300mg/kg) and challenged with a cholinotoxin AF64A. As a result of brain injury and decreased brain acetylcholine level, AF64A induced astrocytic activation, resulting in impairment of learning and memory function. Treatment with SP-NN exerted recovering activities on acetylcholine depletion and brain injury, as well as cognitive deficit induced by AF64A. The results indicate that, in addition to a neuroprotective activity, the SP-NN preparation restores cognitive function of Alzheimer disease model rats by increasing the release of acetylcholine.

  4. THE DUST SUBLIMATION RADIUS AS AN OUTER ENVELOPE TO THE BULK OF THE NARROW Fe Kα LINE EMISSION IN TYPE 1 AGNs

    SciTech Connect

    Gandhi, Poshak; Hönig, Sebastian F.; Kishimoto, Makoto

    2015-10-20

    The Fe Kα emission line is the most ubiquitous feature in the X-ray spectra of active galactic nuclei (AGNs), but the origin of its narrow core remains uncertain. Here, we investigate the connection between the sizes of the Fe Kα core emission regions and the measured sizes of the dusty tori in 13 local Type 1 AGNs. The observed Fe Kα emission radii (R{sub Fe}) are determined from spectrally resolved line widths in X-ray grating spectra, and the dust sublimation radii (R{sub dust}) are measured either from optical/near-infrared (NIR) reverberation time lags or from resolved NIR interferometric data. This direct comparison shows, on an object-by-object basis, that the dust sublimation radius forms an outer envelope to the bulk of the Fe Kα emission. R{sub Fe} matches R{sub dust} well in the AGNs, with the best constrained line widths currently. In a significant fraction of objects without a clear narrow line core, R{sub Fe} is similar to, or smaller than, the radius of the optical broad line region. These facts place important constraints on the torus geometries for our sample. Extended tori in which the solid angle of fluorescing gas peaks at well beyond the dust sublimation radius can be ruled out. We also test for luminosity scalings of R{sub Fe}, finding that the Eddington ratio is not a prime driver in determining the line location in our sample. We also discuss in detail potential caveats of data analysis and instrumental limitations, simplistic line modeling, uncertain black hole masses, and sample selection, showing that none of these is likely to bias our core result. The calorimeter on board Astro-H will soon vastly increase the parameter space over which line measurements can be made, overcoming many of these limitations.

  5. Characterization of the starvation-induced chitinase CfcA and α-1,3-glucanase AgnB of Aspergillus niger.

    PubMed

    van Munster, Jolanda M; Dobruchowska, Justyna M; Veloo, Ruud; Dijkhuizen, Lubbert; van der Maarel, Marc J E C

    2015-03-01

    The common saprophyte Aspergillus niger may experience carbon starvation in nature as well as during industrial fermentations. Starvation survival strategies, such as conidiation or the formation of exploratory hyphae, require energy and building blocks, which may be supplied by autolysis. Glycoside hydrolases are key effectors of autolytic degradation of fungal cell walls, but knowledge on their identity and functionality is still limited. We recently identified agnB and cfcA as two genes encoding carbohydrate-active enzymes that had notably increased transcription during carbon starvation in A. niger. Here, we report the biochemical and functional characterization of these enzymes. AgnB is an α-1,3-glucanase that releases glucose from α-1,3-glucan substrates with a minimum degree of polymerization of 4. CfcA is a chitinase that releases dimers from the nonreducing end of chitin. These enzymes thus attack polymers that are found in the fungal cell wall and may have a role in autolytic fungal cell wall degradation in A. niger. Indeed, cell wall degradation during carbon starvation was reduced in the double deletion mutant ΔcfcA ΔagnB compared to the wild-type strain. Furthermore, the cell walls of the carbon-starved mycelium of the mutant contained a higher fraction of chitin or chitosan. The function of at least one of these enzymes, CfcA, therefore appears to be in the recycling of cell wall carbohydrates under carbon limiting conditions. CfcA thus may be a candidate effector for on demand cell lysis, which could be employed in industrial processes for recovery of intracellular products.

  6. Excess AGN activity in the z = 2.30 Protocluster in HS 1700+64

    NASA Astrophysics Data System (ADS)

    Digby-North, J. A.; Nandra, K.; Laird, E. S.; Steidel, C. C.; Georgakakis, A.; Bogosavljević, M.; Erb, D. K.; Shapley, A. E.; Reddy, N. A.; Aird, J.

    2010-09-01

    We present the results of spectroscopic, narrow-band and X-ray observations of a z = 2.30 protocluster in the field of the QSO HS 1700+643. Using a sample of BX/MD galaxies, which are selected to be at z ~ 2.2-2.7 by their rest-frame ultraviolet colours, we find that there are five protocluster AGN which have been identified by characteristic emission-lines in their optical/near-IR spectra; this represents an enhancement over the field significant at >98.5 per cent confidence. Using a ~200-ks Chandra/ACIS-I observation of this field we detect a total of 161 X-ray point sources to a Poissonian false-probability limit of 4 × 10-6 and identify eight of these with BX/MD galaxies. Two of these are spectroscopically confirmed protocluster members and are also classified as emission-line AGN. When compared to a similarly selected field sample, the analysis indicates this is also evidence for an enhancement of X-ray selected BX/MD AGN over the field, significant at >99 per cent confidence. Deep Lyα narrow-band imaging reveals that a total of 4/123 Lyα emitters (LAEs) are found to be associated with X-ray sources, with two of these confirmed protocluster members and one highly likely member. We do not find a significant enhancement of AGN activity in this LAE sample over that of the field (result is significant at only 87 per cent confidence). The X-ray emitting AGN fractions for the BX/MD and LAE samples are found to be 6.9+9.2-4.4 and 2.9+2.9-1.6 per cent, respectively, for protocluster AGN with L2-10keV >= 4.6 × 1043 erg s-1 at z = 2.30. These findings are similar to results from the z = 3.09 protocluster in the SSA 22 field found by Lehmer et al. (2009), in that both suggest AGN activity is favoured in dense environments at z > 2.

  7. Radio AGN signatures in massive quiescent galaxies out to z=1.5

    NASA Astrophysics Data System (ADS)

    Järvelä, Emilia

    2016-08-01

    Detection of gamma-rays from narrow-line Seyfert 1 galaxies (NLS1) by Fermi confirmed the presence of powerful relativistic jets in them, and thus challenged our understanding of active galactic nuclei (AGN). In the current AGN paradigm powerful relativistic jets are produced in massive elliptical galaxies with supermassive black holes. NLS1s differ from them significantly; they harbour lower mass black holes accreting at higher Eddington ratios, have preferably compact radio morphology, reside mostly in spiral galaxies, and were thought to be radio-quiet.Fermi's discovery invokes questions about the AGN evolution; what triggers and maintains the AGN activity, and what are the evolutionary lines of the different populations? It is also necessary to revise the AGN unification schemes to fit in NLS1s. They convolute the whole AGN scenario, but offer us a new look on the jet phenomena and will help us construct a more comprehensive big picture of AGN.Despite their importance, NLS1s are rather poorly studied as a class. For example, some NLS1s seem to be totally radio-silent, but a considerable fraction are radio-loud and thus probably host jets. This, along with other observational evidence, implies that they do not form a homogeneous class. However, it remains unclear what is triggering the radio loudness in some of them, but, for example, the properties of the host galaxy and the large-scale environment might play a role. Also the parent population of NLS1s remains an open question.We used various statistical methods, for example, multiwavelength correlations and principal component analysis to study a large sample of NLS1 sources. We will present the results and discuss the interplay between their properties, such as emission properties, black hole masses, large-scale environments, and their effect on radio loudness. We will also introduce the Metsähovi Radio Observatory NLS1 galaxy observing programme, which is the first one dedicated to systematical observations

  8. A tale of two feedbacks: Star formation in the host galaxies of radio AGNs

    SciTech Connect

    Karouzos, Marios; Im, Myungshin; Jeon, Yiseul; Kim, Ji Hoon; Trichas, Markos; Goto, Tomo; Malkan, Matt; Ruiz, Angel; Lee, Hyung Mok; Kim, Seong Jin; Oi, Nagisa; Matsuhara, Hideo; Takagi, Toshinobu; Murata, K.; Wada, Takehiko; Wada, Kensuke; Shim, Hyunjin; Hanami, Hitoshi; Serjeant, Stephen; White, Glenn J.; and others

    2014-04-01

    Several lines of argument support the existence of a link between activity at the nuclei of galaxies, in the form of an accreting supermassive black hole, and star formation activity in these galaxies. Radio jets have long been argued to be an ideal mechanism that allows active galactic nuclei (AGNs) to interact with their host galaxies and affect star formation. We use a sample of radio sources in the North Ecliptic Pole (NEP) field to study the nature of this putative link, by means of spectral energy distribution (SED) fitting. We employ the excellent spectral coverage of the AKARI infrared space telescope and the rich ancillary data available in the NEP to build SEDs extending from UV to far-IR wavelengths. We find a significant AGN component in our sample of relatively faint radio sources (AGN component and that of star formation in the host galaxy, independent of the radio luminosity. In contrast, for narrow redshift and AGN luminosity ranges, we find that increasing radio luminosity leads to a decrease in the specific star formation rate. The most radio-loud AGNs are found to lie on the main sequence of star formation for their respective redshifts. For the first time, we potentially see such a two-sided feedback process in the same sample. We discuss the possible suppression of star formation, but not total quenching, in systems with strong radio jets, that supports the maintenance nature of feedback from radio AGN jets.

  9. Microcomputed tomographic analysis of human condyles in unilateral condylar hyperplasia: increased cortical porosity and trabecular bone volume fraction with reduced mineralisation.

    PubMed

    Karssemakers, L H E; Nolte, J W; Tuinzing, D B; Langenbach, G E J; Raijmakers, P G; Becking, A G

    2014-12-01

    Unilateral condylar hyperplasia or hyperactivity is a disorder of growth that affects the mandible, and our aim was to visualise the 3-dimensional bony microstructure of resected mandibular condyles of affected patients. We prospectively studied 17 patients with a clinical presentation of progressive mandibular asymmetry and an abnormal single-photon emission computed tomographic (SPECT) scan. All patients were treated by condylectomy to arrest progression. The resected condyles were scanned with micro-CT (18 μm resolution). Rectangular volumes of interest were selected in 4 quadrants (lateromedial and superoinferior) of the trabecular bone of each condyle. Variables of bone architecture (volume fraction, trabecular number, thickness, and separation, degree of mineralisation, and degree of structural anisotrophy) were calculated with routine morphometric software. Eight of the 17 resected condyles showed clear destruction of the subchondral layer of cortical bone. There was a significant superoinferior gradient for all trabecular variables. Mean (SD) bone volume fraction (25.1 (6) %), trabecular number (1.69 (0.26) mm(-1)), trabecular thickness (0.17 (0.03) mm), and degree of mineralisation (695.39 (39.83) mg HA/cm(3)) were higher in the superior region. Trabecular separation (0.6 (0.16) mm) and structural anisotropy (1.84 (0.28)) were higher in the inferior region. The micro-CT analysis showed increased cortical porosity in many of the condyles studied. It also showed a higher bone volume fraction, greater trabecular thickness and trabecular separation, greater trabecular number, and less mineralisation in the condyles of the 17 patients compared with the known architecture of unaffected mandibular condyles.

  10. Exhaustive exercise increases plasma/serum total oxidation resistance in moderately trained men and women, whereas their VLDL + LDL lipoprotein fraction is more susceptible to oxidation.

    PubMed

    Kaikkonen, J; Porkkala-Sarataho, E; Tuomainen, T P; Nyyssönen, K; Kosonen, L; Ristonmaa, U; Lakka, H M; Salonen, R; Korpela, H; Salonen, J T

    2002-01-01

    The purpose of this study was to evaluate the effects of exhaustive exercise (marathon run) on different lipid peroxidation measurements, including copper-induced serum lipids and VLDL + LDL oxidation susceptibility, and on plasma total antioxidative capacity (TRAP), muscular damage and plasma antioxidants in healthy moderately trained male (n = 21) and female (n = 25) volunteers. Blood samples were taken before and just after the 42-km run. In women, baseline levels of several antioxidative compounds (serum albumin and uric acid, plasma free thiols and blood glutathione) were lower, resulting in 21.5% lower plasma total antioxidative capacity and 70.3% higher serum oxidation susceptibility, compared to men. To compare effects in men and women, the exercise-induced variable changes were adjusted for their baseline levels. After this adjustment, there were no statistically significant differences between the genders in the extent of muscular damage (serum creatine kinase, (CK)), or in the change in serum lipids or VLDL + LDL oxidation susceptibility, or that of plasma antioxidative capacity. A possible beneficial effect of exercise was that serum HDL cholesterol levels increased significantly in both genders, but especially in women. In the group of pooled genders (n=46), the increases in serum CK and in plasma lactate were 190% (95% CI, 133% to 246%) and 109% (95% CI, 65% to 175%), respectively. On the basis of our lipid peroxidation and TRAP measurements, uric acid was observed to be the most important plasma antioxidant. The effect of exercise was to decrease the oxidation susceptibility of serum lipids by 24.8% (95% CI 13.4% to 36.2%) and to elevate plasma TRAP by 14.6% (95% CI, 11.4% to 17.7%). Nonetheless, the oxidation susceptibility of the VLDL + LDL fraction increased by 11.0% (95% CI, 1.9% to 20.2%). Our results suggest that there are no gender-based differences in exhaustive exercise-induced lipid peroxidation or muscular damage. Secondly, even though

  11. AGN flickering on 10-100 kyr timescales

    NASA Astrophysics Data System (ADS)

    Sartori, Lia F.; Schawinski, Kevin; Kill, Bill; Maksym, Peter; Koss, Michael; Argo, Megan; Urry, Meg; Wong, Ivy; Lintott, Chris

    2016-08-01

    The study of AGN variability on timescales of 10^4-10^5 years is important in order to understand the BH - host galaxy interaction and coevolution. The discovery of "Hanny's Voorwerp" (HV), an extended emission line region associated with the nearby galaxy IC 2497, provided us with a laboratory to study AGN variability over such timescales. HV was illuminated by a strong quasar in IC 2497, but this quasar significantly shut down in the last 200 kyrs. Thanks to its recent shutdown we can now explore the host galaxy unimpeded by the presence of a quasar dominating the observations, while the Voorwerp preserves the echoes of its past activity. Recent studies on the optical properties of hard X-ray selected AGN suggest that AGN may flicker on and off hundreds or thousands times with each burst lasting ~10^5 yrs. Systems similar to IC 2497 and HV, the so-called Voorwerpjes, allow us to constrain the last stages of the AGN lifecycle. On the other hand, we recently suggested that the switch on phase may be observed in the so-called optically elusive AGN. In this talk I will review both observational evidence and results from simulation work which support this picture, and explain how optically elusive AGN and Voorwerpjes galaxies can help us to understand different phases of the AGN lifecycle. Moreover, I will discuss possible implications for AGN feedback, BH - host galaxy coevolution, and the analogy between AGN and X-ray binaries accretion physics.

  12. Star-forming galaxies versus low- and high-excitation radio AGN in the VLA-COSMOS 3GHz Large Project

    NASA Astrophysics Data System (ADS)

    Baran, Nikola; Smolcic, Vernesa; Delvecchio, Ivan; Novak, Mladen; Delhaize, Jacinta; Laigle, Clotilde; Ilbert, Olivier; (Vla-)Cosmos Collaboration

    2016-08-01

    We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers the full 2 square degree COSMOS field with mean rms ˜ 2.3 μJy/beam, cataloging 10,899 source components above 5× rms. By combining these radio data with UltraVISTA, optical, nearinfrared, and Spitzer/IRAC mid-infrared data, as well as X-ray data from the Chandra Legacy, Chandra COSMOS surveys, we gain insight into the emission mechanisms within our radio sources out to redshifts of z ˜ 5. From these emission characteristics we classify our sources as star forming galaxies or AGN. Using their multi-wavelength properties we further separate the AGN into sub-samples dominated by radiatively efficient and inefficient AGN, often referred to as high- and low-excitation emission line AGN.We compare our method with other results based on fitting of the sources' spectral energy distributions using both galaxy and AGN spectral models, and those based on the infrared-radio correlation. We study the fractional contributions of these sub-populations down to radio flux levels of ˜10 μJy. We find that at 3 GHz flux densities above ˜400 μJy quiescent, red galaxies, consistent with the low-excitation radio AGN class constitute the dominant fraction. Below densities of ˜200 μJy star-forming galaxies begin to constitute the largest fraction, followed by the low-excitation, and X-ray- and IR-identified high-excitation radio AGN.

  13. Flavanoid-rich fraction from Sageretia theezans leaves scavenges reactive oxygen radical species and increases the resistance of low-density lipoprotein to oxidation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To explore their bioactive fractions, S. theezans leaves were extracted 2 with 60% acetone and then fractionated sequentially with hexane, ethyl acetate, and water. ROS (HOCl, ONOO-, and O2 deg -) scavenging activity, ORAC value and total phenolic content of each fraction were investigated. The ethy...

  14. Sprint-interval but not continuous exercise increases PGC-1α protein content and p53 phosphorylation in nuclear fractions of human skeletal muscle

    PubMed Central

    Granata, Cesare; Oliveira, Rodrigo S. F.; Little, Jonathan P.; Renner, Kathrin; Bishop, David J.

    2017-01-01

    Sprint interval training has been reported to induce similar or greater mitochondrial adaptations to continuous training. However, there is limited knowledge about the effects of different exercise types on the early molecular events regulating mitochondrial biogenesis. Therefore, we compared the effects of continuous and sprint interval exercise on key regulatory proteins linked to mitochondrial biogenesis in subcellular fractions of human skeletal muscle. Nineteen men, performed either 24 min of moderate-intensity continuous cycling at 63% of WPeak (CE), or 4 × 30-s “all-out” cycling sprints (SIE). Muscle samples (vastus lateralis) were collected pre-, immediately (+0 h) and 3 (+3 h) hours post-exercise. Nuclear p53 and PHF20 protein content increased at +0 h, with no difference between groups. Nuclear p53 phosphorylation and PGC-1α protein content increased at +0 h after SIE, but not CE. We demonstrate an exercise-induced increase in nuclear p53 protein content, an event that may relate to greater p53 stability - as also suggested by increased PHF20 protein content. Increased nuclear p53 phosphorylation and PGC-1α protein content immediately following SIE but not CE suggests these may represent important early molecular events in the exercise-induced response to exercise, and that SIE is a time-efficient and possibly superior option than CE to promote these adaptations. PMID:28281651

  15. Sprint-interval but not continuous exercise increases PGC-1α protein content and p53 phosphorylation in nuclear fractions of human skeletal muscle.

    PubMed

    Granata, Cesare; Oliveira, Rodrigo S F; Little, Jonathan P; Renner, Kathrin; Bishop, David J

    2017-03-10

    Sprint interval training has been reported to induce similar or greater mitochondrial adaptations to continuous training. However, there is limited knowledge about the effects of different exercise types on the early molecular events regulating mitochondrial biogenesis. Therefore, we compared the effects of continuous and sprint interval exercise on key regulatory proteins linked to mitochondrial biogenesis in subcellular fractions of human skeletal muscle. Nineteen men, performed either 24 min of moderate-intensity continuous cycling at 63% of WPeak (CE), or 4 × 30-s "all-out" cycling sprints (SIE). Muscle samples (vastus lateralis) were collected pre-, immediately (+0 h) and 3 (+3 h) hours post-exercise. Nuclear p53 and PHF20 protein content increased at +0 h, with no difference between groups. Nuclear p53 phosphorylation and PGC-1α protein content increased at +0 h after SIE, but not CE. We demonstrate an exercise-induced increase in nuclear p53 protein content, an event that may relate to greater p53 stability - as also suggested by increased PHF20 protein content. Increased nuclear p53 phosphorylation and PGC-1α protein content immediately following SIE but not CE suggests these may represent important early molecular events in the exercise-induced response to exercise, and that SIE is a time-efficient and possibly superior option than CE to promote these adaptations.

  16. The effect of AGN feedback on the X-ray morphologies of clusters: Simulations vs. observations

    NASA Astrophysics Data System (ADS)

    Chon, Gayoung; Puchwein, Ewald; Böhringer, Hans

    2016-07-01

    , which increases the tension with observations. When classified as non-relaxed or relaxed according to their w and P3/P0 values, we find that there are no relaxed clusters in the simulations with the AGN feedback. This suggests that not only global cluster properties, like LX and T, and radial profiles should be used to compare and to calibrate simulations with observations, but also substructure measures like centre shifts and power ratios. Finally, we discuss what changes in the simulations might ease the tension with observational constraints on these quantities.

  17. The Extended Fe Distribution in the Intracluster Medium and the Implications Regarding AGN Heating

    NASA Astrophysics Data System (ADS)

    David, Laurence P.; Nulsen, Paul E. J.

    2008-12-01

    We present a systematic analysis of XMM-Newton observations of eight cool-core clusters of galaxies and determine the Fe distribution in the intracluster medium relative to the stellar distribution in the central dominant galaxy (CDG). Our analysis shows that the Fe is significantly more extended than the stellar mass in the CDG in all of the clusters in our sample, with a slight trend of increasing extent with increasing central cooling time. The excess Fe within the central 100 kpc in these clusters can be produced by Type Ia supernovae from the CDG over the past 3-7 Gyr. Since the excess Fe primarily originates from the CDG, it is a useful probe for determining the motion of the gas and the mechanical energy deposited by AGN outbursts over the past ~5 Gyr in the centers of clusters. We explore two possible mechanisms for producing the greater extent of the Fe relative to the stars in the CDG, bulk expansion of the gas and turbulent diffusion of the Fe. Assuming that the gas and Fe expand together, we find that a total energy of 1060-1061 erg s-1 must have been deposited into the central 100 kpc of these clusters in order to produce the currently observed Fe distributions. Since the required enrichment time for the excess Fe is approximately 5 Gyr in these clusters, this gives an average AGN mechanical power over this time of 1043-1044 erg s-1. The extended Fe distribution in cluster cores can also arise from turbulent diffusion. Assuming a steady state (i.e., the outward mass flux of Fe across a given surface is equal to the mass injection rate of Fe within that surface), we find that diffusion coefficients of 1029-1030 cm2 s-1 are required in order to maintain the currently observed Fe profiles. We find that heating by both turbulent diffusion of entropy and dissipation are important heating mechanisms in cluster cores. In half of the clusters with central cooling times greater than 1 Gyr, we find that heating by turbulent diffusion of entropy alone can balance

  18. The Lick AGN Monitoring Project 2016: Extending Reverberation Mapping to Higher Luminosity AGNs

    NASA Astrophysics Data System (ADS)

    U, Vivian; LAMP2016 Collaboration

    2017-01-01

    The technique of reverberation mapping has been used to estimate virial black hole masses and, more fundamentally, to probe the broad line region structure in Seyfert I galaxies. Efforts from the previous Lick AGN Monitoring Project (LAMP) campaigns and other studies to date have culminated in a large sample of reverberation mapped AGNs and measurements of their black hole masses, which in turn enabled major improvement to various AGN scaling relations. However, the high-luminosity end of such relations remains poorly constrained; this is because of observational challenges presented by the weaker continuum flux variations and longer time dilation in these sources. To this end, we have initiated a new LAMP2016 campaign to target AGNs with luminosities of 10^44 erg/s, with predicted H-beta lags of ~20 - 60 days or black hole masses of 10^7 - 10^8.5 Msun. Designed to monitor ~20 AGNs biweekly from Spring 2016 through Winter 2017 with the Kast spectrograph on the 3-m Shane Telescope at Lick Observatory, we aim to probe luminosity-dependent trends in broad line region structure and dynamics, improve calibrations for single-epoch estimates of high-redshift quasar black hole masses, and test photoionization models for the radially-stratified structure of the broad line region. In this talk, I will present the overview and scope of LAMP2016 and show preliminary results from our ongoing campaign.

  19. AGN feedback in the Perseus cluster

    NASA Astrophysics Data System (ADS)

    Gendron-Marsolais, Marie-Lou; Hlavacek-Larrondo, Julie; Clarke, Tracy E.; Intema, Huib; Fabian, Andrew C.; Taylor, Gregory B.; Blundell, Katherine

    2016-04-01

    Deep Chandra images of the Perseus cluster of galaxies have revealed a succession of cavities created by the jets of the central supermassive black hole, pushing away the X-ray emitting gas and leaving bubbles filled with radio emission. Perseus is one of the rare examples showing buoyantly rising lobes from past radio outbursts, characterized by a steep spectral index and known as ghost cavities. All of these structures trace the complete history of mechanical AGN feedback over the past 500 Myrs. I will present results on new, ultra deep 230-470 MHz JVLA data. This low-frequency view of the Perseus cluster will probe the old radio-emitting electron population and will allow us to build the most detailed map of AGN feedback in a cluster thus far.

  20. 'Harder when Brighter' Spectral Variability in Low-Luminosity AGN

    NASA Astrophysics Data System (ADS)

    Connolly, S.; McHardy, I.; Skipper, C.; Dwelly, T.

    2015-07-01

    We present X-ray spectral variability of four low accretion rate AGN - M81, NGC 1097, NGC 1052 and NGC 3998 - as observed by Swift and RXTE. All four objects were selected due to having spectra which hardened with increasing count rate, converse to the `softer when brighter' behaviour normally observed in AGN with higher accretion rates. The spectra were summed in flux bins and fitted with a variety of models. A simple absorbed power law model was found to fit the spectra of M81, NGC 1097 and NGC 3998 well, whilst NGC 1052 required a partially covered power law model. In all four cases, the most likely main source of spectral variability is found to be luminosity-dependent changes in the photon index of the power law component. An anticorrelation between the photon index and the count rate is found in all of the sources. The anticorrelation is likely to be caused by accretion via a radiatively-inefficient accretion flow, expected in low-Eddington ratio systems such as these, and/or due to the presence of a jet. This behaviour is similar to that seen in the `hard state' of X-ray binaries, implying that these LLAGN are in a similar state.

  1. Simulations of the OzDES AGN reverberation mapping project

    SciTech Connect

    King, Anthea L.; Martini, Paul; Davis, Tamara M.; Denney, K. D.; Kochanek, C. S.; Peterson, Bradley M.; Skielboe, Andreas; Vestergaard, Marianne; Huff, Eric; Watson, Darach; Banerji, Manda; McMahon, Richard; Sharp, Rob; Lidman, C.

    2015-08-26

    As part of the Australian spectroscopic dark energy survey (OzDES) we are carrying out a large-scale reverberation mapping study of ~500 quasars over five years in the 30 deg2 area of the Dark Energy Survey (DES) supernova fields. These quasars have redshifts ranging up to 4 and have apparent AB magnitudes between 16.8 mag < r < 22.5 mag. The aim of the survey is to measure time lags between fluctuations in the quasar continuum and broad emission-line fluxes of individual objects in order to measure black hole masses for a broad range of active galactic nuclei (AGN) and constrain the radius–luminosity (R–L) relationship. Here we investigate the expected efficiency of the OzDES reverberation mapping campaign and its possible extensions. We expect to recover lags for ~35–45 % of the quasars. AGN with shorter lags and greater variability are more likely to yield a lag measurement, and objects with lags ≲6 months or ~1 yr are expected to be recovered the most accurately. The baseline OzDES reverberation mapping campaign is predicted to produce an unbiased measurement of the R–L relationship parameters for Hβ, MgIIλ2798, and C IVλ1549. As a result, extending the baseline survey by either increasing the spectroscopic cadence, extending the survey season, or improving the emission-line flux measurement accuracy will significantly improve the R–L parameter constraints for all broad emission lines.

  2. Study of the mid-infrared properties of obscured AGN

    NASA Astrophysics Data System (ADS)

    Severgnini, P.; Caccianiga, A.; della Ceca, R.

    2008-10-01

    The comprehension of the physical properties of obscured AGNs is one of the main goals of the high energy astronomy given their key role in tracing the accretion history of the Universe. Although X-ray and infrared data of AGN with a different level of absorption could provide a direct tool to test the predictions of the AGN models, only few sparse SED of obscured AGN are available so far. We present here the results obtained from Spitzer observations of a statistically complete sample of obscured AGN drawn from the XMM-Newton Hard Bright Sample. This is the largest hard X-ray sample with a complete spectroscopic identification. The Spitzer data, combined with good X-ray and optical spectroscopic data, has allowed us to define powerful diagnostic plots to select heavily obscured AGNs and to build up their spectral energy distributions.

  3. AGES: THE AGN AND GALAXY EVOLUTION SURVEY

    SciTech Connect

    Kochanek, C. S.; Eisenstein, D. J.; Caldwell, N.; Jones, C.; Murray, S. S.; Forman, W. R.; Green, P.; Cool, R. J.; Assef, R. J.; Eisenhardt, P.; Stern, D.; Jannuzi, B. T.; Dey, A.; Brown, M. J. I.; Gonzalez, A. H.

    2012-05-01

    The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7 deg{sup 2} of the Booetes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23,745 redshifts. There are well-defined galaxy samples in 10 bands (the B{sub W} , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 {mu}m, and MIPS 24 {mu}m bands) to a limiting magnitude of I < 20 mag for spectroscopy. For these galaxies, we obtained 18,163 redshifts from a sample of 35,200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085 < z < 0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24 {mu}m sources to fainter limiting magnitudes (I < 22.5 mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshift estimates are provided for all sources in the AGES samples.

  4. Unification of Low Luminosity AGN and Hard State X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Connolly, S.

    2015-09-01

    We present X-ray spectral variability of four low accretion rate and low luminosity AGN (LLAGN)- M81, NGC 1097, NGC 1052 and NGC 3998 - as observed by Swift and RXTE. All four objects were selected due to having spectra which hardened with increasing count rate, converse to the 'softer when brighter' behaviour normally observed in AGN with higher accretion rates. The spectra were summed in flux bins and fitted with a variety of models. A simple absorbed power law model was found to fit the spectra of M81, NGC 1097 and NGC 3998 well, whilst NGC 1052 required a partially covered power law model. In all four cases, the most likely cause of spectral variability is found to be hardening of the photon index of the power law component with increasing luminosity. Such a correlation has been seen previously within samples of low accretion rate AGN but in only one case has it been seen within observations of a single AGN. Here we show that such behaviour may be very common in LLAGN. A similar anticorrelation is found in X-ray binary systems in the 'hard state', at low accretion rates similar to those of the LLAGN discussed here. Our observations thus imply that LLAGN are the active galaxy equivalent of hard state X-ray binaries.

  5. Shaping the X-ray spectrum of galaxy clusters with AGN feedback and turbulence

    NASA Astrophysics Data System (ADS)

    Gaspari, M.

    2015-07-01

    The hot plasma filling galaxy clusters emits copious X-ray radiation. The classic unheated and unperturbed cooling flow model predicts dramatic cooling rates and an isobaric X-ray spectrum with constant differential luminosity distribution. The observed cores of clusters (and groups) show instead a strong deficit of soft X-ray emission: dLx/dT ∝ (T/Thot)α = 2 ± 1. Using 3D hydrodynamic simulations, we show that such deficit arises from the tight self-regulation between thermal instability condensation and AGN outflow injection: condensing clouds boost the AGN outflows, which quench cooling as they thermalize through the core. The resultant average distribution slope is α ≃ 2, oscillating within the observed 1 < α < 3. In the absence of thermal instability, the X-ray spectrum remains isothermal (α ≳ 8), while unopposed cooling drives a too shallow slope, α < 1. AGN outflows deposit their energy inside-out, releasing more heat in the inner cooler phase; radially distributed heating alone induces a declining spectrum, 1 < α < 2. Turbulence further steepens the spectrum and increases the scatter: the turbulent Mach number in the hot phase is subsonic, while it becomes transonic in the cooler phase, making perturbations to depart from the isobaric mode. Such increase in dln P/dln T leads to α ≈ 3. Self-regulated AGN outflow feedback can address the soft X-ray problem through the interplay of heating and turbulence.

  6. Intermediate inclinations of type 2 Coronal-Line Forest AGN

    NASA Astrophysics Data System (ADS)

    Rose, Marvin; Elvis, Martin; Crenshaw, Michael; Glidden, Ana

    2015-07-01

    Coronal-Line Forest Active Galactic Nuclei (CLiF AGN) are remarkable in the sense that they have a rich spectrum of dozens of coronal emission lines (e.g. [Fe VII], [Fe X] and [Ne V]) in their spectra. Rose, Elvis & Tadhunter suggest that the inner obscuring torus wall is the most likely location of the coronal line region in CLiF AGN, and the unusual strength of the forbidden high-ionization lines is due to a specific AGN-torus inclination angle. Here, we test this suggestion using mid-IR colours (4.6-22 μm) from the Wide-Field Infrared Survey Explorer for the CLiF AGN. We use the Fischer et al. result that showed that as the AGN-torus inclination becomes more face on, the Spitzer 5.5-30 μm colours become bluer. We show that the [W2-W4] colours for the CLiF AGN (<[W2-W4]> = 5.92 ± 0.12) are intermediate between Sloan Digital Sky Survey (SDSS) type 1 (<[W2-W4]> = 5.22 ± 0.01) and type 2 AGN (<[W2-W4]> = 6.35 ± 0.03). This implies that the AGN-torus inclinations for the CLiF AGN are indeed intermediate, supporting the work of Rose, Elvis & Tadhunter. The confirmed relation between CLiF AGN and their viewing angle shows that CLiF AGN may be useful for our understanding of AGN unification.

  7. Ultra-fast outflows (aka UFOs) from AGNs and QSOs

    NASA Astrophysics Data System (ADS)

    Cappi, M.; Tombesi, F.; Giustini, M.

    During the last decade, strong observational evidence has been accumulated for the existence of massive, high velocity winds/outflows (aka Ultra Fast Outflows, UFOs) in nearby AGNs and in more distant quasars. Here we briefly review some of the most recent developments in this field and discuss the relevance of UFOs for both understanding the physics of accretion disk winds in AGNs, and for quantifying the global amount of AGN feedback on the surrounding medium.

  8. The Prevalence of Gas Outflows in Type 2 AGNs. II. 3D Biconical Outflow Models

    NASA Astrophysics Data System (ADS)

    Bae, Hyun-Jin; Woo, Jong-Hak

    2016-09-01

    We present 3D models of biconical outflows combined with a thin dust plane for investigating the physical properties of the ionized gas outflows and their effect on the observed gas kinematics in type 2 active galactic nuclei (AGNs). Using a set of input parameters, we construct a number of models in 3D and calculate the spatially integrated velocity and velocity dispersion for each model. We find that three primary parameters, i.e., intrinsic velocity, bicone inclination, and the amount of dust extinction, mainly determine the simulated velocity and velocity dispersion. Velocity dispersion increases as the intrinsic velocity or the bicone inclination increases, while velocity (i.e., velocity shifts with respect to systemic velocity) increases as the amount of dust extinction increases. Simulated emission-line profiles well reproduce the observed [O iii] line profiles, e.g., narrow core and broad wing components. By comparing model grids and Monte Carlo simulations with the observed [O iii] velocity-velocity dispersion distribution of ˜39,000 type 2 AGNs, we constrain the intrinsic velocity of gas outflows ranging from ˜500 to ˜1000 km s-1 for the majority of AGNs, and up to ˜1500-2000 km s-1 for extreme cases. The Monte Carlo simulations show that the number ratio of AGNs with negative [O iii] velocity to AGNs with positive [O iii] velocity correlates with the outflow opening angle, suggesting that outflows with higher intrinsic velocity tend to have wider opening angles. These results demonstrate the potential of our 3D models for studying the physical properties of gas outflows, applicable to various observations, including spatially integrated and resolved gas kinematics.

  9. The Keck OSIRIS Nearby AGN (KONA) Survey: AGN Fueling and Feedback

    NASA Astrophysics Data System (ADS)

    Hicks, Erin K. S.; Müller-Sánchez, Francisco; Malkan, Matthew A.; Yu, Po-Chieh

    In an effort to better constrain the relevant physical processes dictating the co-evolution of supermassive black holes and the galaxies in which they reside we turn to local Seyfert AGN. It is only with these local AGN that we can reach the spatial resolution needed to adequately characterize the inflow and outflow mechanisms thought to be the driving forces in establishing the relationship between black holes and their host galaxies at higher redshift. We present the first results from the KONA (Keck OSIRIS Nearby AGN) survey, which takes advantage of the integral field unit OSIRIS plus laser and natural guide star adaptive optics to probe down to scales of 5-30 parsecs in a sample of 40 local Seyfert galaxies. With these K-band data we measure the two-dimensional distribution and kinematics of the nuclear stars, molecular gas, and ionized gas within the central few hundred parsecs.

  10. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    NASA Astrophysics Data System (ADS)

    Assef, R. J.; Walton, D. J.; Brightman, M.; Stern, D.; Alexander, D.; Bauer, F.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Finkelstein, S. L.; Hickox, R. C.; Tsai, C.-W.; Wu, J. W.

    2016-03-01

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13-050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M⊙ yr-1. Deep polarimetry observations could confirm the reflection hypothesis.

  11. HOT DUST OBSCURED GALAXIES WITH EXCESS BLUE LIGHT: DUAL AGN OR SINGLE AGN UNDER EXTREME CONDITIONS?

    SciTech Connect

    Assef, R. J.; Diaz-Santos, T.; Walton, D. J.; Brightman, M.; Stern, D.; Eisenhardt, P. R. M.; Tsai, C.-W.; Alexander, D.; Bauer, F.; Blain, A. W.; Finkelstein, S. L.; Hickox, R. C.; Wu, J. W.

    2016-03-10

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13–050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M{sub ⊙} yr{sup −1}. Deep polarimetry observations could confirm the reflection hypothesis.

  12. AGN Triggering in Kpc-scale Separation Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Comerford, Julia M.

    2017-01-01

    As supermassive black holes in galaxy mergers evolve from Mpc to mpc separations, the kpc-scale separations are pivotal for igniting AGN activity. At these separations the galaxy mergers drive central inflows of gas, which can trigger AGN activity in one or both supermassive black holes, in systems known as offset AGN and dual AGN, respectively. Offset and dual AGN are direct tracers of the connection between galaxy mass growth (via galaxy mergers) and supermassive black hole mass growth (via gas accretion). These systems are also the smallest separation supermassive black hole pairs that have been observationally confirmed, offering the last glimpse of supermassive black hole pair dynamics before gravitational wave emission dominates and drives the coalescence of the supermassive black holes. I will present multiwavelength approaches to building catalogs of offset AGN and dual AGN, and show the results of our observing campaigns with HST, Chandra, VLA, and Keck. Finally, I will discuss what our results show about whether galaxy mergers preferentially fuel the most luminous AGN, which supermassive black hole in a merger is more efficient at accreting gas, and where in a merger the AGN fueling occurs.

  13. AGN physics - A Chandra-Swift Census of AGN activity in Compact Groups

    NASA Astrophysics Data System (ADS)

    Tzanavaris, Panayiotis

    2012-09-01

    We present a missing link in the study of AGN activity in compact groups of galaxies. The level of this activity in compact groups remains controversial, but has only been studied with optical and infrared diagnostics. We present the first systematic study of 40 compact group galaxies in 9 groups, combining Chandra and Swift data, and providing the first X-ray/UV view of galactic nuclei in compact groups. Our results provide independent evidence that the level of AGN activity in compact groups is representative of their unique environment, which is distinct to that of rich clusters and the field.

  14. AGN Luminosity and Stellar Age: Two Missing Ingredients for AGN Unification as Seen with iPTF Supernovae

    NASA Astrophysics Data System (ADS)

    Villarroel, Beatriz; Nyholm, Anders; Karlsson, Torgny; Comerón, Sébastien; Korn, Andreas J.; Sollerman, Jesper; Zackrisson, Erik

    2017-03-01

    Active galactic nuclei (AGNs) are extremely powerful cosmic objects, driven by accretion of hot gas upon super-massive black holes. The zoo of AGN classes is divided into two major groups, with Type-1 AGNs displaying broad Balmer emission lines and Type-2 narrow ones. For a long time it was believed that a Type-2 AGN is a Type-1 AGN viewed through a dusty kiloparsec-sized torus, but an emerging body of observations suggests more than just the viewing angle matters. Here we report significant differences in supernova (SN) counts and classes in the first study to date of SNe near Type-1 and Type-2 AGN host galaxies, using data from the intermediate Palomar Transient Factory, the Sloan Digital Sky Survey Data Release 7, and Galaxy Zoo. We detect many more SNe in Type-2 AGN hosts (size of effect ∼5.1σ) compared to Type-1 hosts, which shows that the two classes of AGN are located inside host galaxies with different properties. In addition, Type-1 and Type-2 AGNs that are dominated by star formation according to Wide-field Infrared Survey Explorer colors {m}W1-{m}W2< 0.5 and are matched in 22 μm absolute magnitude differ by a factor of ten in L[O iii] λ5007 luminosity, suggesting that when residing in similar types of host galaxies Type-1 AGNs are much more luminous. Our results demonstrate two more factors that play an important role in completing the current picture: the age of stellar populations and the AGN luminosity. This has immediate consequences for understanding the many AGN classes and galaxy evolution.

  15. A simple way to improve AGN feedback prescription in SPH simulations

    NASA Astrophysics Data System (ADS)

    Zubovas, Kastytis; Bourne, Martin A.; Nayakshin, Sergei

    2016-03-01

    Active galactic nuclei (AGN) feedback is an important ingredient in galaxy evolution, however its treatment in numerical simulations is necessarily approximate, requiring subgrid prescriptions due to the dynamical range involved in the calculations. We present a suite of smoothed particle hydrodynamics simulations designed to showcase the importance of the choice of a particular subgrid prescription for AGN feedback. We concentrate on two approaches to treating wide-angle AGN outflows: thermal feedback, where thermal and kinetic energy is injected into the gas surrounding the supermassive black hole (SMBH) particle, and virtual particle feedback, where energy is carried by tracer particles radially away from the AGN. We show that the latter model produces a far more complex structure around the SMBH, which we argue is a more physically correct outcome. We suggest a simple improvement to the thermal feedback model - injecting the energy into a cone, rather than spherically symmetrically - and show that this markedly improves the agreement between the two prescriptions, without requiring any noticeable increase in the computational cost of the simulation.

  16. Increasing cellulose accessibility is more important than removing lignin: a comparison of cellulose solvent-based lignocellulose fractionation and soaking in aqueous ammonia.

    PubMed

    Rollin, Joseph A; Zhu, Zhiguang; Sathitsuksanoh, Noppadon; Zhang, Y-H Percival

    2011-01-01

    While many pretreatments attempt to improve the enzymatic digestibility of biomass by removing lignin, this study shows that improving the surface area accessible to cellulase is a more important factor for achieving a high sugar yield. Here we compared the pretreatment of switchgrass by two methods, cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF) and soaking in aqueous ammonia (SAA). Following pretreatment, enzymatic hydrolysis was conducted at two cellulase loadings, 15 filter paper units (FPU)/g glucan and 3 FPU/g glucan, with and without BSA blocking of lignin absorption sites. The hydrolysis results showed that the lignin remaining after SAA had a significant negative effect on cellulase performance, despite the high level of delignification achieved with this pretreatment. No negative effect due to lignin was detected for COSLIF-treated substrate. SEM micrographs, XRD crystallinity measurements, and cellulose accessibility to cellulase (CAC) determinations confirmed that COSLIF fully disrupted the cell wall structure, resulting in a 16-fold increase in CAC, while SAA caused a 1.4-fold CAC increase. A surface plot relating the lignin removal, CAC, and digestibility of numerous samples (both pure cellulosic substrates and lignocellulosic materials pretreated by several methods) was also developed to better understand the relative impacts of delignification and CAC on glucan digestibility.

  17. HEAVILY OBSCURED AGN IN STAR-FORMING GALAXIES AT z approx = 2

    SciTech Connect

    Treister, E.; Kartaltepe, Jeyhan; Le Floc'h, Emeric; Cardamone, Carolin N.; Schawinski, Kevin; Urry, C. Megan; Virani, Shanil; Gawiser, Eric; Lira, Paulina; Damen, Maaike; Taylor, Edward N.; Justham, Stephen; Koekemoer, Anton M.

    2009-11-20

    We study the properties of a sample of 211 heavily obscured active galactic nucleus (AGN) candidates in the extended Chandra Deep Field-South selecting objects with f {sub 24m}u{sub m}/f{sub R} > 1000 and R - K>4.5. Of these, 18 were detected in X-rays and found to be obscured AGNs with neutral hydrogen column densities of approx10{sup 23} cm{sup -2}. In the X-ray-undetected sample, the following evidence suggests a large fraction of heavily obscured (Compton-thick) AGN: (1) The stacked X-ray signal of the sample is strong, with an observed ratio of soft to hard X-ray counts consistent with a population of approx90% heavily obscured AGNs combined with 10% star-forming galaxies. (2) The X-ray-to-mid-IR ratios for these sources are significantly larger than that of star-forming galaxies and approx2 orders of magnitude smaller than for the general AGN population, suggesting column densities of N {sub H} approx> 5 x 10{sup 24} cm{sup -2}. (3) The Spitzer near- and mid-IR colors of these sources are consistent with those of the X-ray-detected samples if the effects of dust self-absorption are considered. Spectral fitting to the rest-frame UV/optical light (dominated by the host galaxy) returns stellar masses of approx10{sup 11} M{sub sun} and (E(B - V)) = 0.5, and reveals evidence for a significant young stellar population, indicating that these sources are experiencing considerable star formation. This sample of heavily obscured AGN candidates implies a space density at z approx 2 of approx10{sup -5} Mpc{sup -3}, finding a strong evolution in the number of L{sub X} >10{sup 44} erg s{sup -1} sources from z = 1.5 to 2.5, possibly consistent with a short-lived heavily obscured phase before an unobscured quasar is visible.

  18. Feedback in the local Universe: Relation between star formation and AGN activity in early type galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher; Baum, Stefi; Jones, Christine; Forman, William; Whitmore, Samantha; Ahmed, Rabeea; Pierce, Katherine; Leary, Sara

    2015-08-01

    Aim: We address the relation between star formation and AGN activity in a large sample of nearby early type (E and S0) galaxies. The redshift range of the galaxies is 0.0002AGN is believed to play an important role in regulating star formation and thus the process of galaxy evolution and formation. Evidence of AGN feedback is found in massive galaxies in galaxy clusters. However, how common AGN feedback is in the local universe and in small scale systems is still not evident.Methods: To answer this question, we carried out a multiple wavelength study of a sample of 231 early type galaxies which were selected to have an apparent K-band magnitude brighter than 13.5 and whose positions correlate with Chandra ACIS-I and ACIS-S sources. The galaxies in the sample are unbiased regarding their star formation and radio source properties. Using the archival observations at radio, IR and UV from VLA, WISE and GALEX respectively, we obtained the radio power, estimate FUV star formation rate (SFR) and other galaxy properties to study AGN activity and ongoing star formation.Results: The relationship between radio power and stellar mass shows that there is an upper envelope of radio power that is a steep function of stellar luminosity. This suggests that less massive galaxies have low radio power while massive galaxies are capable of hosting powerful radio sources. The Radio-MIR relation shows that galaxies with P>=1022 WHz-1 are potential candidates for being AGN. About ~ 7% of the sample show evidence of ongoing star formation with SFR ranging from 10-3 to 1 M⊙yr-1. These are also less massive and radio faint suggesting the absence of active accretion. There is nearly equal fraction of star forming galaxies in radio faint (P<1022 WHz-1) and radio bright galaxies (P>=1022 WHz-1) . Only ~ 5% of the galaxies in our sample have P>=1022 WHz-1 and most of them do not show evidence of bright accretion disks. We see a weak correlation and a dispersion of

  19. Star formation and AGN activity in the most luminous LINERs in the local universe

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Povic, M.; Netzer, H.; Masegosa, J.; Nordon, R.; Pérez, E.; Schoenell, W.

    2017-03-01

    This work presents the properties of 42 objects in the group of the most luminous, highest star formation rate (SFR) low-ionization nuclear emission-line regions (LINERs) at z = 0.04 - 0.11. We obtained long-slit spectroscopy of the nuclear regions for all sources, and FIR data (Herschel and IRAS) for 13 of them.We measured emission-line intensities, extinction, stellar populations, stellar masses, ages, active galactic nuclei (AGN) luminosities, and SFRs. We find considerable differences from other low-redshift LINERs, and general similarity to star-forming galaxies. We confirm the existence of such luminous LINERs in the local universe, after being previously detected at z˜0.3 by Tommasin et al. The median stellar mass of these LINERs corresponds to 6 - 7× 10^{10} M_⊙ which was found in previous works to correspond to the peak of relative growth rate of stellar populations and therefore for the highest SFRs. Other LINERs although showing similar AGN luminosities have lower SFR. We find that most of these sources have LAGN ˜ LSF suggesting co-evolution of black hole and stellarmass. In general, the fraction of local LINERs on the main sequence of star-forming galaxies is related to their AGN luminosity.

  20. Star formation and AGN activity in the most luminous LINERs in the local universe

    NASA Astrophysics Data System (ADS)

    Pović, Mirjana; Márquez, Isabel; Netzer, Hagai; Masegosa, Josefa; Nordon, Raanan; Pérez, Enrique; Schoenell, William

    2016-11-01

    This work presents the properties of 42 objects in the group of the most luminous, highest star formation rate (SFR) low-ionization nuclear emission-line regions (LINERs) at z = 0.04-0.11. We obtained long-slit spectroscopy of the nuclear regions for all sources, and FIR data (Herschel and IRAS) for 13 of them. We measured emission-line intensities, extinction, stellar populations, stellar masses, ages, active galactic nuclei (AGN) luminosities, and SFRs. We find considerable differences from other low-redshift LINERs, in terms of extinction, and general similarity to star-forming galaxies. We confirm the existence of such luminous LINERs in the local universe, after being previously detected at z ˜ 0.3 by Tommasin et al. The median stellar mass of these LINERs corresponds to 6-7 × 1010 M⊙ which was found in previous work to correspond to the peak of relative growth rate of stellar populations and therefore for the highest SFRs. Other LINERs although showing similar AGN luminosities have lower SFR. We find that most of these sources have LAGN ˜ LSF suggesting co-evolution of black hole and stellar mass. In general, the fraction of local LINERs on the main sequence of star-forming galaxies is related to their AGN luminosity.

  1. The Global Implications of the Hard X-ray Excess in Type 1 AGN

    NASA Astrophysics Data System (ADS)

    Tatum, Malachi; Turner, T.; Miller, L.; Reeves, J.

    2013-04-01

    Suzaku observations of 1H 0419-577 and PDS 456, both type 1 AGN, revealed a marked 'hard excess' of flux above 10 keV, likely due to the presence of a Compton-thick absorber covering a large fraction of the continuum source. The discovery is intriguing, given the clear view to the optical BLR in type 1 objects. These results motivated an exploratory study of the hard excess phenomenon in the local type 1 AGN population, using the Swift Burst Alert Telescope (BAT). We selected radio quiet type 1 - 1.9 AGN from the 58-month BAT catalog and cross-correlated them with the holdings in the Suzaku public archive. The hardness of the X-ray spectrum, combined with measurements of the equivalent width of Fe Ka emission suggest that type 1 X-ray spectra are shaped by an ensemble of Compton-thick clouds, partially covering the continuum. I discuss our methodology, the observational findings and the possible location of the Compton-thick gas.

  2. Pitch fractionation. Technical report

    SciTech Connect

    Weinberg, V.L.; White, J.L.

    1981-12-15

    Petroleum pitch (Ashland A240) has been subjected to thermal treatment and solvent fractionation to produce refined pitches to be evaluated as impregnants for carbon-carbon composites. The solvent fractions were obtained by sequential Soxhlet extraction with solvents such as hexane, cyclohexane, toluene, and pyridine. The most severe thermal treatment produced a mesophase pitch (approximately 50% mesophase); an appreciable portion of the mesophase was soluble in strong solvents. There were substantial differences in chemical composition and in pyrolysis behavior of the fractions. As the depth of fraction increased, the pyrolysis yield and bloating increased, and the microstructure of the coke became finer until glassy microconstituents were formed in the deepest fractions.

  3. THE ROLE OF STAR FORMATION AND AN AGN IN DUST HEATING OF z = 0.3–2.8 GALAXIES. I. EVOLUTION WITH REDSHIFT AND LUMINOSITY

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Sajina, Anna; Roebuck, Eric; Yan, Lin; Armus, Lee; Díaz-Santos, Tanio; Stierwalt, Sabrina

    2015-11-20

    We characterize infrared spectral energy distributions of 343 (ultra)luminous infrared galaxies from z = 0.3–2.8. We diagnose the presence of an active galactic nucleus (AGN) by decomposing individual Spitzer mid-IR spectroscopy into emission from star formation and an AGN-powered continuum; we classify sources as star-forming galaxies (SFGs), AGNs, or composites. Composites comprise 30% of our sample and are prevalent at faint and bright S{sub 24}, making them an important source of IR AGN emission. We combine spectroscopy with multiwavelength photometry, including Herschel imaging, to create three libraries of publicly available templates (2–1000 μm). We fit the far-IR emission using a two-temperature modified blackbody to measure cold and warm dust temperatures (T{sub c} and T{sub w}). We find that T{sub c} does not depend on mid-IR classification, while T{sub w} shows a notable increase as the AGN grows more luminous. We measure a quadratic relationship between mid-IR AGN emission and total AGN contribution to L{sub IR}. AGNs, composites, and SFGs separate in S{sub 8}/S{sub 3.6} and S{sub 250}/S{sub 24}, providing a useful diagnostic for estimating relative amounts of these sources. We estimate that >40% of IR-selected samples host an AGN, even at faint selection thresholds (S{sub 24} > 100 μJy). Our decomposition technique and color diagnostics are relevant given upcoming observations with the James Webb Space Telescope.

  4. The Keck OSIRIS Nearby AGN Survey: Tracing Inflow within the Central 200 pc of Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Hicks, Erin K. S.; Müller-Sánchez, Francisco; Malkan, Matthew A.; Yu, Po-Chieh

    2016-08-01

    In an effort to identify the fundamental processes driving feeding and feedback in AGN we turn to local Seyfert galaxies and rely on a multi-wavelength approach. With the integral field unit OSIRIS and adaptive optics we characterize the nuclear stars and gas down to scales of 5-30 parsecs in a sample of 40 Seyfert galaxies with the Keck OSIRIS Nearby AGN (KONA) survey. The complex gas kinematics in these near-IR data are interpreted using an integrative approach through comparison with data available at a range of wavelengths. We present first results from the survey with a focus on work aimed at constraining the mechanism(s) driving inflow of material within the central 200 pc. Particularly useful in the identification of inflow mechanisms (e.g. nuclear spiral, external accretion) is spatial correlation of the molecular gas distribution and kinematics with dust features revealed in HST imaging (optical and near-IR). Also informative is comparison with X-ray emission to identify locations likely influenced by interactions with outflows. The stellar kinematics in the sample galaxies (traced by CO bandheads at 2.3 microns) indicate a stellar population within the central few 100 parsecs in circular rotation, and in the majority of the galaxies the molecular gas (traced by H2 emission at 2.1218 microns) is found to have a rotating component co-spatial with the stellar disk. A significant fraction of the galaxies also exhibit kinematic signatures of inflow superimposed on this disk rotation, with inflow driven by secular and non-secular processes identified. We explore statistical trends of the nuclear stellar and molecular gas properties, including primary fueling mechanism, with Seyfert type, AGN luminosity, and host environment with the goal of disentangling which properties are fundamental to the nature of the AGN.

  5. Cause and Effect of Feedback: Multiphase Gas in Cluster Cores Heated by AGN Jets

    NASA Astrophysics Data System (ADS)

    Gaspari, M.; Ruszkowski, M.; Sharma, P.

    2012-02-01

    Multiwavelength data indicate that the X-ray-emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To a large extent, cooling is offset by heating due to active galactic nuclei (AGNs) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (t TI/t ff) falls below a critical threshold of ≈10. When this happens, dense cold gas decouples from the hot intracluster medium (ICM) phase and generates inhomogeneous and spatially extended Hα filaments. These cold gas clumps and filaments "rain" down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with t TI/t ff > 10. Eventually, the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever t TI/t ff <~ 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.

  6. Warm Absorber Diagnostics of AGN Dynamics

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy

    Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are

  7. AGN Feedback in Clusters of Galaxies

    DTIC Science & Technology

    2010-01-01

    bubbles created by the radio lobes evacuating regions of the ICM vary widely from a few kpc (e.g. Abell 262 [21, 22]) to hundreds of kpc (e.g. MS0735.6...diameters of approximately 200 kpc . The total energy injection required to inflate the cavities and produce the ob- served shocks is 6 × 1061 erg...cluster center, and these are modeled as shocks in [32] based on the earlier 163 ksec dataset. These features are at 31 and 46 kpc from the AGN and the

  8. Obscured AGN With NuSTAR

    NASA Astrophysics Data System (ADS)

    Marinucci, Andrea; Bianchi, S.; Matt, G.; Balokovic, M.; Bauer, F. E.; Brandt W. N.; Gandhi, P.; Guainazzi, M.; Harrison, F.; Iwasawa, K.; Nicastro, F.; Puccetti, S.; Ricci, C.; Walton, D. J.; Stern, D.

    2016-10-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first orbiting telescope to focus high energy X-ray light above 10 keV. Compared to the previous generation of coded mask observatories, this change in technology provides NuSTAR with 10x sharper images and 100x improved sensitivityThe unprecedented spectral quality in the 3-80 keV band has provided unique information about the circumnuclear reflecting environment of AGNI will present and discuss results from the NuSTAR observations of nearby Obscured AGN in its first four years of science.

  9. The detection and X-ray view of the changing look AGN HE 1136-2304

    NASA Astrophysics Data System (ADS)

    Parker, M. L.; Komossa, S.; Kollatschny, W.; Walton, D. J.; Schartel, N.; Santos-Lleó, M.; Harrison, F. A.; Fabian, A. C.; Zetzl, M.; Grupe, D.; Rodríguez-Pascual, P. M.; Vasudevan, R. V.

    2016-09-01

    We report the detection of high-amplitude X-ray flaring of the AGN HE 1136-2304, which is accompanied by a strong increase in the flux of the broad Balmer lines, changing its Seyfert type from almost type 2 in 1993 down to 1.5 in 2014. HE 1136-2304 was detected by the XMM-Newton slew survey at >10 times the flux it had in the ROSAT all-sky survey, and confirmed with Swift follow-up after increasing in X-ray flux by a factor of ˜30. Optical spectroscopy with SALT shows that the AGN has changed from a Seyfert 1.95 to a Seyfert 1.5 galaxy, with greatly increased broad line emission and an increase in blue continuum AGN flux by a factor of >4. The X-ray spectra from XMM-Newton and NuSTAR reveal moderate intrinsic absorption and a high energy cutoff at ˜100 keV. We consider several different physical scenarios for a flare, such as changes in obscuring material, tidal disruption events, and an increase in the accretion rate. We find that the most likely cause of the increased flux is an increase in the accretion rate, although it could also be due to a change in obscuration.

  10. Clues to the Structure of AGN Through Massive Variability Surveys

    NASA Astrophysics Data System (ADS)

    Lawrence, A.

    2016-06-01

    Variability studies hold information on otherwise unresolvable regions in Active Galactic Nuclei (AGN). Population studies of large samples likewise have been very productive for our understanding of AGN. These two themes are coming together in the idea of systematic variability studies of large samples - with SDSS, PanSTARRS, and soon, LSST. I summarise what we have learned about the optical and UV variability of AGN, and what it tells us about accretion discs and the BLR. The most exciting recent results have focused on rare large-scale outbursts and collapses - Tidal Disruption Events, changing-look AGN, and large amplitude microlensing. All of these promise to give us new insight into AGN physics.

  11. Searching for Compton-thick AGN with INTEGRAL

    NASA Astrophysics Data System (ADS)

    Virani, S. N.; Treister, E.; Urry, C. M.; Maccarone, T.; Bird, T.; Beckmann, V.; Lira, P.; Coppi, P.; Uchiyama, Y.

    2005-12-01

    The 30 keV peak in the X-ray background strongly suggests there should be a large number of highly obscured AGN in the local universe. However, the exact number of these objects remains unknown, even though they could nearly double the space density of supermassive black holes. These Compton-thick AGN can be detected in the hard X-rays with INTEGRAL. As part of the current observing cycle, we were awarded 2 Msec to perform INTEGRAL imaging of the XMM-LSS field in order to find highly obscured AGN in the local Universe. In this paper, we present preliminary results for the ˜1 Ms of IBIS data obtained so far, including new hard X-ray detections of AGN. We also present the 20---200 keV spectra of the brightest AGN including the z<0.1 Seyfert galaxies NGC 788, NGC 1068, and NGC 1142.

  12. A UV to mid-IR study of AGN selection

    SciTech Connect

    Chung, Sun Mi; Kochanek, Christopher S.; Assef, Roberto; Brown, Michael J. I.; Stern, Daniel; Jannuzi, Buell T.; Gonzalez, Anthony H.; Hickox, Ryan C.; Moustakas, John

    2014-07-20

    We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 deg{sup 2} Boötes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC and MIPS) data, as well as spectroscopic redshifts for ∼20,000 objects, primarily from the AGN and Galaxy Evolution Survey. We fit galaxy, active galactic nucleus (AGN), stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. The photometric redshift precision of the galaxy and AGN samples are σ/(1 + z) = 0.040 and σ/(1 + z) = 0.169, respectively, with the worst 5% outliers excluded. On the basis of the χ{sub ν}{sup 2} of the SED fit for each SED model, we are able to distinguish between Galactic and extragalactic sources for sources brighter than I = 23.5 mag. We compare the SED fits for a galaxy-only model and a galaxy-AGN model. Using known X-ray and spectroscopic AGN samples, we confirm that SED fitting can be successfully used as a method to identify large populations of AGNs, including spatially resolved AGNs with significant contributions from the host galaxy and objects with the emission line ratios of 'composite' spectra. We also use our results to compare with the X-ray, mid-IR, optical color, and emission line ratio selection techniques. For an F-ratio threshold of F > 10, we find 16,266 AGN candidates brighter than I = 23.5 mag and a surface density of ∼1900 AGN deg{sup –2}.

  13. Dietary fat elevates hepatic apoA-I production by increasing the fraction of apolipoprotein A-I mRNA in the translating pool.

    PubMed

    Azrolan, N; Odaka, H; Breslow, J L; Fisher, E A

    1995-08-25

    Elevated plasma high density lipoprotein cholesterol (HDL-C) levels are associated with a decreased risk for coronary heart disease. Ironically, diets enriched in saturated fat and cholesterol (HF/HC diets), which tend to accelerate atherosclerotic processes by increasing LDL cholesterol levels, also raise HDL-C. We have recently reported, using a human apoA-I (hapoA-1) transgenic mouse model, that the elevation of HDL-C by a HF/HC diet is attributable, in part, to an increase in the hepatic production of hapoA-1. To further define the hepatocellular processes associated with this induction, we have prepared primary hepatocytes from hapoA-1 transgenic mice. Rates of hapoA-1 secretion were 40% greater from cells prepared from animals fed the HF/HC relative to a low fat-low cholesterol (LF/LC) control diet. The abundance of hapoA-1 mRNA in these cells was similar between hepatocytes prepared from the HF/HC and LF/LC diet fed animals, suggesting a post-transcriptional mechanism that does not involve mRNA stability. Inhibition of secretion using brefeldin A revealed an increase in cellular hapoA-1 accumulation. Thus, the HF/HC diet apparently affects hepatic hapoA-1 production via a mechanism that is manifest prior to the exit of newly synthesized hapoA-1 from the Golgi. Pulse-chase experiments revealed a 39% greater peak hapoA-1 synthesis, with no difference in the degradation of total labeled hapoA-1 protein, as a result of the HF/HC diet feeding. Finally, resolution of liver S10 extracts via sucrose density sedimentation and metrizamide density equilibrium gradient centrifugation analyses both revealed similar increases (31 and 24%, respectively) in the relative percentage of hapoA-1 mRNA associated with the translating polysomal fractions as a result of the HF/HC feeding. Together, these data suggest that the HF/HC diet affects hepatic hapoA-1 production via a specific modulation in the relative amount of hapoA-1 mRNA in the polysomal pool. These observations

  14. The jet-disc connection in AGN

    NASA Astrophysics Data System (ADS)

    Sbarrato, T.; Padovani, P.; Ghisellini, G.

    2014-11-01

    We present our latest results on the connection between accretion rate and relativistic jet power in active galactic nuclei (AGN), by using a large sample which includes mostly blazars, but contains also some radio galaxies. The jet power can be traced by γ-ray luminosity in the case of blazars, and radio luminosity for both classes. The accretion-disc luminosity is instead traced by the broad emission lines. Among blazars, we find a correlation between broad line emission and the γ-ray or radio luminosities, suggesting a direct tight connection between jet power and accretion rate. We confirm that the observational differences between blazar subclasses reflect differences in the accretion regime, but with blazars only we cannot properly access the low-accretion regime. By introducing radio galaxies, we succeed in observing the fingerprint of the transition between radiatively efficient and inefficient accretion discs in the jetted AGN family. The transition occurs at the standard critical value Ld/LEdd ˜ 10-2 and it appears smooth. Below this value, the ionizing luminosity emitted by the accretion structure drops significantly.

  15. Extremely efficient Zevatron in rotating AGN magnetospheres

    NASA Astrophysics Data System (ADS)

    Osmanov, Z.; Mahajan, S.; Machabeli, G.; Chkheidze, N.

    2014-12-01

    A novel model of particle acceleration in the magnetospheres of rotating active galactic nuclei (AGN) is constructed. The particle energies may be boosted up to 1021 eV in a two-step mechanism: in the first stage, the Langmuir waves are centrifugally excited and amplified by means of a parametric process that efficiently pumps rotational energy to excite electrostatic fields. In the second stage, the electrostatic energy is transferred to particle kinetic energy via Landau damping made possible by rapid `Langmuir collapse'. The time-scale for parametric pumping of Langmuir waves turns out to be small compared to the kinematic time-scale, indicating high efficiency of the first process. The second process of `Langmuir collapse' - the creation of caverns or low-density regions - also happens rapidly for the characteristic parameters of the AGN magnetosphere. The Langmuir collapse creates appropriate conditions for transferring electric energy to boost up already high particle energies to much higher values. It is further shown that various energy loss mechanism are relatively weak, and do not impose any significant constraints on maximum achievable energies.

  16. Using a 3% Proton Density Fat Fraction as a Cut-off Value Increases Sensitivity of Detection of Hepatic Steatosis, Based on Results from Histopathology Analysis.

    PubMed

    Nasr, Patrik; Forsgren, Mikael F; Ignatova, Simone; Dahlström, Nils; Cedersund, Gunnar; Leinhard, Olof Dahlqvist; Norén, Bengt; Ekstedt, Mattias; Lundberg, Peter; Kechagias, Stergios

    2017-03-09

    It is possible to estimate hepatic triglyceride content by calculating the proton density fat fraction (PDFF), using proton magnetic resonance spectroscopy ((1)H-MRS), instead of collecting and analyzing liver biopsies to detect steatosis. However, the current PDFF cut-off value (5%) used to define steatosis by magnetic resonance was derived from studies that did not use histopathology as the reference standard. We performed a prospective study to determine the accuracy of (1)H-MRS PDFF in measurement of steatosis using histopathology analysis as the standard. We collected clinical, serologic, (1)H-MRS PDFF, and liver biopsy data from 94 adult patients with increased levels of liver enzymes (6 months or more) referred to the Department of Gastroenterology and Hepatology at Linköping University Hospital in Sweden from 2007 through 2014. Steatosis was graded using the conventional histopathology method and fat content was quantified in biopsy samples using stereological point counts (SPCs). We correlated (1)H-MRS PDFF findings with SPCs (r = 0.92; P <.001). (1)H-MRS PDFF results correlated with histopathology results (ρ = 0.87; P <.001), and SPCs correlated with histopathology results (ρ = 0.88; P <.001). All 25 subjects with PDFF values of 5.0% or more had steatosis based on histopathology findings (100% specificity for PDFF). However, of 69 subjects with PDFF values below 5.0% (negative result), 22 were determined to have steatosis based on histopathology findings (53% sensitivity for PDFF). Reducing the PDFF cut-off value to 3.0% identified patients with steatosis with 100% specificity and 79% sensitivity; a PDFF cut-off value of 2.0% identified patients with steatosis with 94% specificity and 87% sensitivity. These findings might be used to improve non-invasive detection of steatosis.

  17. Simulations of the OzDES AGN reverberation mapping project

    DOE PAGES

    King, Anthea L.; Martini, Paul; Davis, Tamara M.; ...

    2015-08-26

    As part of the Australian spectroscopic dark energy survey (OzDES) we are carrying out a large-scale reverberation mapping study of ~500 quasars over five years in the 30 deg2 area of the Dark Energy Survey (DES) supernova fields. These quasars have redshifts ranging up to 4 and have apparent AB magnitudes between 16.8 mag < r < 22.5 mag. The aim of the survey is to measure time lags between fluctuations in the quasar continuum and broad emission-line fluxes of individual objects in order to measure black hole masses for a broad range of active galactic nuclei (AGN) and constrainmore » the radius–luminosity (R–L) relationship. Here we investigate the expected efficiency of the OzDES reverberation mapping campaign and its possible extensions. We expect to recover lags for ~35–45 % of the quasars. AGN with shorter lags and greater variability are more likely to yield a lag measurement, and objects with lags ≲6 months or ~1 yr are expected to be recovered the most accurately. The baseline OzDES reverberation mapping campaign is predicted to produce an unbiased measurement of the R–L relationship parameters for Hβ, MgIIλ2798, and C IVλ1549. As a result, extending the baseline survey by either increasing the spectroscopic cadence, extending the survey season, or improving the emission-line flux measurement accuracy will significantly improve the R–L parameter constraints for all broad emission lines.« less

  18. VizieR Online Data Catalog: X-ray variability of AGNs in Lockman Hole (Papadakis+, 2008)

    NASA Astrophysics Data System (ADS)

    Papadakis, I. E.; Chatzopoulos, E.; Athanasiadis, D.; Markowitz, A.; Georgantopoulos, I.

    2008-05-01

    We present the results from a detailed X-ray variability analysis of 66 AGN in the Lockman Hole, which have optical spectroscopic identifications. We compare, quantitatively, their variability properties with the properties of local AGN, and we study the "variability - luminosity" relation as a function of redshift, and the "variability - redshift" relation in two luminosity bins. We use archival data from the last 10 XMM-Newton observations of the Lockman Hole field to extract light curves in the rest frame, 2-10keV band. We use the "normalized excess variance" to quantify the variability amplitude. Using the latest results regarding the AGN power spectral shape and its dependence on black hole mass and accretion rate, we are able to compute model "variability - luminosity" curves, which we compare with the relations we observe. When we consider all the sources in our sample, we find that their variability amplitude decreases with increasing redshift and luminosity. (1 data file).

  19. Subaru adaptive-optics high-spatial-resolution infrared K- and L'-band imaging search for deeply buried dual AGNs in merging galaxies

    SciTech Connect

    Imanishi, Masatoshi; Saito, Yuriko

    2014-01-01

    We present the results of infrared K- (2.2 μm) and L'-band (3.8 μm) high-spatial-resolution (<0.''2) imaging observations of nearby gas- and dust-rich infrared luminous merging galaxies, assisted by the adaptive optics system on the Subaru 8.2 m telescope. We investigate the presence and frequency of red K – L' compact sources, which are sensitive indicators of active galactic nuclei (AGNs), including AGNs that are deeply buried in gas and dust. We observed 29 merging systems and confirmed at least one AGN in all but one system. However, luminous dual AGNs were detected in only four of the 29 systems (∼14%), despite our method's being sensitive to buried AGNs. For multiple nuclei sources, we compared the estimated AGN luminosities with supermassive black hole (SMBH) masses inferred from large-aperture K-band stellar emission photometry in individual nuclei. We found that mass accretion rates onto SMBHs are significantly different among multiple SMBHs, such that larger-mass SMBHs generally show higher mass accretion rates when normalized to SMBH mass. Our results suggest that non-synchronous mass accretion onto SMBHs in gas- and dust-rich infrared luminous merging galaxies hampers the observational detection of kiloparsec-scale multiple active SMBHs. This could explain the significantly smaller detection fraction of kiloparsec-scale dual AGNs when compared with the number expected from simple theoretical predictions. Our results also indicate that mass accretion onto SMBHs is dominated by local conditions, rather than by global galaxy properties, reinforcing the importance of observations to our understanding of how multiple SMBHs are activated and acquire mass in gas- and dust-rich merging galaxies.

  20. X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

    NASA Technical Reports Server (NTRS)

    Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

    2013-01-01

    Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density

  1. Mechanically fractionated flour isolated from green bananas (M. cavendishii var. nanica) as a tool to increase the dietary fiber and phytochemical bioactivity of layer and sponge cakes.

    PubMed

    Segundo, Cristina; Román, Laura; Gómez, Manuel; Martínez, Mario M

    2017-03-15

    This article describes the effect of mechanically fractionated flours from green bananas on the nutritional, physical and sensory attributes of two types of cakes (sponge and layer). A plausible 30% replacement of banana flour in the formulation of layer cakes is demonstrated, finding only a small decline in the sensory perception. On the contrary, sponge cakes were noticeable worsened with the use of banana flours (lower specific volume, worse sensory attributes and higher hardness), which was minimized when using fine flour. Both layer and sponge cakes exhibited an enhancement of the resistant starch and dietary fiber content with the replacement of green banana flour (up to a fivefold improvement in RS performance). Moreover, sponge cakes yielded more polyphenols and antioxidant capacity with banana flours, especially with the coarse fraction. Therefore, results showed that a mechanical fractionation allowed a feasible nutritional enhancement of cakes with the use of banana flours.

  2. Mini-Survey on SDSS OIII AGN with Swift

    NASA Technical Reports Server (NTRS)

    Angelini, Lorella

    2008-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. There is a common wisdom that every massive galaxy has a massive black hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low $L_X$ (at all $z$). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of {it optically-selected samples} shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [O{\\sc iii}] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a min-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([O{\\sc iii}]) to check the relation with the $L_X$ observed with Swift.

  3. Decursin in Angelica gigas Nakai (AGN) Enhances Doxorubicin Chemosensitivity in NCI/ADR-RES Ovarian Cancer Cells via Inhibition of P-glycoprotein Expression.

    PubMed

    Choi, Hyeong Sim; Cho, Sung-Gook; Kim, Min Kyoung; Kim, Min Soo; Moon, Seung Hee; Kim, Il Hwan; Ko, Seong-Gyu

    2016-12-01

    Angelica gigas Nakai (AGN, Korean Dang-gui) is traditionally used for the treatment of various diseases including cancer. Here, we investigated multidrug-resistant phenotype-reversal activities of AGN and its compounds (decursin, ferulic acid, and nodakenin) in doxorubicin-resistant NCI/ADR-RES ovarian cancer cells. Our results showed that a combination of doxorubicin with either AGN or decursin inhibited a proliferation of NCI/ADR-RES cells. These combinations increased the number of cells at sub-G1 phase when cells were stained with Annexin V-fluorescein isothiocyanate. We also found that these combinations activated caspase-9, caspase-8, and caspase-3 and increased cleaved PARP level. Moreover, an inhibition of P-glycoprotein expression by either AGN or decursin resulted in a reduction of its activity in NCI/ADR-RES cells. Therefore, our data demonstrate that decursin in AGN inhibits doxorubicin-resistant ovarian cancer cell proliferation and induces apoptosis in the presence of doxorubicin via blocking P-glycoprotein expression. Therefore, AGN would be a potentially novel treatment option for multidrug-resistant tumors by sensitizing to anticancer agents. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Disentangling AGN and Star Formation in Soft X-Rays

    NASA Technical Reports Server (NTRS)

    LaMassa, Stephanie M.; Heckman, T. M.; Ptak, A.

    2012-01-01

    We have explored the interplay of star formation and active galactic nucleus (AGN) activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low-resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft emission of 34 Sy2s using power-law and thermal models. For the 11 sources with high signal-to-noise Chandra imaging of the diffuse host galaxy emission, we estimate the luminosity due to star formation by removing the AGN, fitting the residual emission. The AGN and star formation contributions to the soft X-ray luminosity (i.e., L(sub x,AGN) and L(sub x,SF)) for the remaining 24 Sy2s were estimated from the power-law and thermal luminosities derived from spectral fitting. These luminosities were scaled based on a template derived from XSINGS analysis of normal star-forming galaxies. To account for errors in the luminosities derived from spectral fitting and the spread in the scaling factor, we estimated L(sub x,AGN) and L(sub x,SF))from Monte Carlo simulations. These simulated luminosities agree with L(sub x,AGN) and L(sub x,SF) derived from Chandra imaging analysis within a 3sigma confidence level. Using the infrared [Ne ii]12.8 micron and [O iv]26 micron lines as a proxy of star formation and AGN activity, respectively, we independently disentangle the contributions of these two processes to the total soft X-ray emission. This decomposition generally agrees with L(sub x,SF) and L(sub x,AGN) at the 3 sigma level. In the absence of resolvable nuclear emission, our decomposition method provides a reasonable estimate of emission due to star formation in galaxies hosting type 2 AGNs.

  5. Physical properties of simulated galaxy populations at z = 2 - I. Effect of metal-line cooling and feedback from star formation and AGN

    NASA Astrophysics Data System (ADS)

    Haas, Marcel R.; Schaye, Joop; Booth, C. M.; Dalla Vecchia, Claudio; Springel, Volker; Theuns, Tom; Wiersma, Robert P. C.

    2013-11-01

    We use hydrodynamical simulations from the OverWhelmingly Large Simulations (OWLS) project to investigate the dependence of the physical properties of galaxy populations at redshift 2 on metal-line cooling and feedback from star formation and active galactic nuclei (AGN). We find that if the sub-grid feedback from star formation is implemented kinetically, the feedback is only efficient if the initial wind velocity exceeds a critical value. This critical velocity increases with galaxy mass and also if metal-line cooling is included. This suggests that radiative losses quench the winds if their initial velocity is too low. If the feedback is efficient, then the star formation rate is inversely proportional to the amount of energy injected per unit stellar mass formed (which is proportional to the initial mass loading for a fixed wind velocity). This can be understood if the star formation is self-regulating, i.e. if the star formation rate (and thus the gas fraction) increases until the outflow rate balances the inflow rate. Feedback from AGN is efficient at high masses, while increasing the initial wind velocity with gas pressure or halo mass allows one to generate galaxy-wide outflows at all masses. Matching the observed galaxy mass function requires efficient feedback. In particular, the predicted faint-end slope is too steep unless we resort to highly mass loaded winds for low-mass objects. Such efficient feedback from low-mass galaxies (M* ≪ 1010 M⊙) also reduces the discrepancy with the observed specific star formation rates, which are higher than predicted unless the feedback transitions from highly efficient to inefficient just below M* ˜ 5 × 109 M⊙.

  6. The Swift AGN and Cluster Survey

    NASA Astrophysics Data System (ADS)

    Danae Griffin, Rhiannon; Dai, Xinyu; Kochanek, Christopher S.; Bregman, Joel N.; Nugent, Jenna

    2016-01-01

    The Swift active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg^2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding X-ray bursts to provide a medium depth (4 × 10^-15 erg cm^-2 s^-1) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here, we present the first two papers in a series of publications for SACS. In the first paper, we introduce our method and catalog of 22,563 point sources and 442 extended sources. We examine the number counts of the AGN and galaxy cluster populations. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The depth and areal coverage of SACS is well suited for galaxy cluster surveys outside the local universe, reaching z ˜ 1 for massive clusters. In the second paper, we use Sloan Digital Sky Survey (SDSS) DR8 data to study the 203 extended SACS sources that are located within the SDSS footprint. We search for galaxy over-densities in 3-D space using SDSS galaxies and their photometric redshifts near the Swift galaxy cluster candidates. We find 103 Swift clusters with a > 3σ over-density. The remaining targets are potentially located at higher redshifts and require deeper optical follow-up observations for confirmations as galaxy clusters. We present a series of cluster properties including the redshift, BCG magnitude, BCG-to-X-ray center offset, optical richness, X-ray luminosity and red sequences. We compare the observed redshift distribution of the sample with a theoretical model, and find that our sample is complete for z ≤ 0.3 and 80% complete for z ≤ 0.4, consistent with the survey depth of SDSS. We also match our SDSS confirmed Swift clusters to existing cluster catalogs, and find 42, 2 and 1 matches in optical, X-ray and SZ catalogs, respectively, so the majority of these

  7. X-ray-selected AGNs near bright galaxies

    NASA Technical Reports Server (NTRS)

    Stocke, John T.; Schneider, Peter; Morris, Simon L.; Gioia, Isabella M.; Maccacaro, Tommaso

    1987-01-01

    Among the numerous low-redshift low-luminosity X-ray sources discovered with the Einstein Observatory, ten AGNs were identified that are projected within three optical diameters of bright (V less than 18) foreground galaxies. These AGNs near galaxies have significantly higher redshifts than the sample as a whole. This discovery is interpreted in terms of gravitational 'microlensing' in which stars in the foreground galaxy have significantly brightened the X-ray emission from these higher redshift AGNs, allowing their detection. It is suggested that microlensing may be responsible for a significant alteration of the inherent QSO luminosity function.

  8. Proteomic analysis of post-nuclear supernatant fraction and percoll-purified membranes prepared from brain cortex of rats exposed to increasing doses of morphine

    PubMed Central

    2014-01-01

    ; Aspartate aminotransferase, ↓2.2×] origin. Surprisingly, the immunoblot analysis of the same PM resolved by 2D-ELFO indicated that the “active”, morphine-induced pool of Gβ subunits represented just a minor fraction of the total signal of Gβ which was decreased 1.2x only. The dominant signal of Gβ was unchanged. Conclusion Brain cortex of rats exposed to increasing doses of morphine is far from being adapted. Significant up-regulation of proteins functionally related to oxidative stress and apoptosis suggests a major change of energy metabolism resulting in the state of severe brain cell “discomfort” or even death. PMID:24528483

  9. AGN warm absorption with the ATHENA

    NASA Astrophysics Data System (ADS)

    Różańska, Agata; Gronkiewicz, Dominik; Hryniewicz, Krzysztof; Adhikari, Tek Prasad; Rataj, Mirosław; Skup, Konrad

    2016-06-01

    X-ray astronomy requires satellites to make progress in searching the distribution of hot matter in the Universe. Approximately 15 years period of time is needed for full construction of the flight instrument from the mission concept up to the launch. A new generation X-ray telescope ATHENA (the Advanced Telescope for High Energy Astrophysics) was approved by European Space Agency as a large mission with a launch foreseen in 2028. In this paper we show how microcalorimeter on the board of ATHENA will help us to study warm absorption observed in active galactic nuclei (AGN). We show that future observations will allow us to identify hundreds of lines from highly ionized elements and to measure Galactic warm absorption with very high precision.

  10. Neutrino radiation of the AGN black holes

    NASA Astrophysics Data System (ADS)

    Ter-Kazarian, G.; Shidhani, S.; Sargsyan, L.

    2007-07-01

    In the framework of ‘microscopic’ theory of black holes (J. Phys. Soc. Jpn. Suppl. B 70, 84, 2001; Astrophys. USSR 4, 659, 1996; 35, 335, 1991, 33, 143, 1990, 31, 345, 1989a; Astrophys. Space Sci. 1, 1992; Dokl. Akad. Nauk USSR 309, 97, 1989b), and references therein, we address the ‘pre-radiation time’ (PRT) of neutrinos from black holes, which implies the lapse of time from black hole’s birth till radiation of an extremely high energy neutrinos. For post-PRT lifetime, the black hole no longer holds as a region of spacetime that cannot communicate with the external universe. We study main features of spherical accretion onto central BH and infer a mass accretion rate onto it, and, further, calculate the resulting PRT versus bolometric luminosity due to accretion onto black hole. We estimate the PRTs of AGN black holes, with the well-determined masses and bolometric luminosities, collected from the literature by Woo Jong-Hak and Urry (Astrophys. J. 579, 530, 2002) on which this paper is partially based. The simulations for the black holes of masses M BH ≃(1.1ṡ106 ÷4.2ṡ109) M ⊙ give the values of PRTs varying in the range of about T BH ≃(4.3ṡ105 ÷5.6ṡ1011) yr. The derived PRTs for the 60 AGN black holes are longer than the age of the universe (˜13.7 Gyr) favored today. At present, some of remaining 174 BHs may radiate neutrinos. However, these results would be underestimated if the reservoir of gas for accretion in the galaxy center is quite modest, and no obvious way to feed the BHs with substantial accretion.

  11. Herschel Observed Stripe 82 Quasars and Their Host Galaxies: Connections between AGN Activity and host Galaxy Star Formation

    NASA Astrophysics Data System (ADS)

    Dong, X. Y.; Wu, Xue-Bing

    2016-06-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 1046.4 erg s-1. The redshift range of this sample is within z < 4, with a mean value of 1.5 ± 0.78. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 M ⊙ yr-1 and the mean gas mass is ˜1011.3 M ⊙. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z = 2. It is correlated with the AGN bolometric luminosity, where {L}{{FIR}}\\propto {L}{{Bol}}0.46+/- 0.03. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L FIR and L Bol has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M BH/M * ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M BH-M * scaling relation.

  12. AGN STORM: A Leap Forward In Reverberation Mapping

    NASA Astrophysics Data System (ADS)

    Dalla Bontà, Elena; AGN STORM Team

    2016-10-01

    Reverberation mapping is a tomographic technique that can be used to determine the structure and kinematics of the broad- line emitting region at the center of active galactic nuclei. By-products of these investigations are the masses of the central black holes and information about the structure of the accretion disk. I will show some of the most recent results from the AGN Space Telescope and Optical Reverberation Mapping (AGN STORM) project, which was built around 180 daily observations of the bright Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope. AGN STORM included observations made with Swift, XMM, and several ground-based telescopes, including the 1.22-m telescope at Asiago Observatory. Elena Dalla Bonta` on behalf of the AGN STORM Team.

  13. AGN-selected clusters as revealed by weak lensing

    NASA Technical Reports Server (NTRS)

    Wold, M.; Lacy, M.; Dahle, H.; Lilje, P. B.; Ridgway, S. E.

    2002-01-01

    We discuss the results in light of the cooling flow and the merger/interaction scenarios for triggering and fuelling AGN in clusters, but find that the data do not point unambiguously to neither of the two.

  14. K-Ras mutant fraction in A/J mouse lung increases as a function of benzo[a]pyrene dose

    EPA Science Inventory

    K-Ras mutant fraction (MF) was measured to examine the default assumption of low dose linearity in the benzo[a]pyrene (B[a]P) mutational response. Groups of ten male A/J mice (7-9 weeks-old) received a single i.p. injection of 0, 0.05, 0.5, 5, or 50 mg/kg B[a]P, and were sacrifi...

  15. Multiwavelength Number Counts of AGN in the GOODS Fields

    NASA Astrophysics Data System (ADS)

    Urry, C. M.; Treister, E.; Chatzichristou, E. T.; Van Duyne, J.; Bauer, F. E.; Alexander, D. M.; Koekemoer, A. M.; Moustakas, L. A.; Brandt, W. N.; Grogin, N. A.; Bergeron, J.; Stern, D.; Chary, R.-R.; Conselice, C. J.; Cristiani, S.

    2004-05-01

    We model the X-ray, optical, and far-infrared flux distributions of AGN in the GOODS fields, starting from hard X-ray luminosity functions and spectral energy distributions appropriate to the unified scheme for AGN. The deep optical counts measured from HST ACS images can be well explained by a unified scheme that postulates roughly 3 times as many obscured as unobscured AGN. This scenario is consistent with the observed spectroscopic and photometric redshift distributions of the GOODS AGN once selection effects are considered. The previously reported discrepancy between observed spectroscopic redshift distributions and the predictions of population synthesis models for the X-ray background (which include a similarly large number of obscured AGN) is explained by bias against the most heavily obscured AGN in both X-ray surveys and optical spectroscopic samples. We present the model predictions for the number counts of AGN in the Spitzer MIPS 24 micron and IRAC 3.6-8 micron bands. The GOODS Spitzer observations will verify whether large numbers of obscured AGN are indeed present in the early Universe; these will be very bright far-infrared sources, including some, missed by X-ray observations, that look like ultraluminous infrared galaxies. Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc, under NASA contract NAS5-26555. This work was supported by NASA grants HST-GO-09425(.01-A,.13-A,.26-A); NSF CAREER award AST 99-83783; NASA contract number 1224666 issued by JPL/Caltech under NASA contract 1407; ASI grant I/R/088/02; and a Royal Society University Research Fellowship.

  16. Broad Band Properties of the BAT Selected AGN

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard; Winter, Lisa; Tueller, jack

    2008-01-01

    We will present the x-ray spectral properties of approximately 150 Burst Alert Telescope (BAT) selected active galactic nuclei (AGN) focusing on the issues of spectral complexity, x-ray absorption and its distribution and that contribution of sources to the x-ray background. If time permits we will also present the nature of the host galaxies of the AGN and their relationship to merger candidates.

  17. OT1_dweedman_1: Comparing [CII] 158 micron Luminosities to Spectral Properties of Luminous Starburst Galaxies and AGN

    NASA Astrophysics Data System (ADS)

    Weedman, D.

    2010-07-01

    Herschel PACS spectroscopy of the [CII] emission line at 158 microns is proposed for a carefully selected sample of 123 sources that already have complete low and high resolution mid-infrared spectra between 5 microns and 35 microns from the Spitzer Infrared Spectrograph, and which also have spectral energy distributions (SEDs) from IRAS and Akari photometry. [CII] 158 um is the strongest far-infrared emission line and therefore crucial to compare with other features in luminous, dusty galaxies. Sources have 0.004 < z < 0.34 and 43.0 < log L(IR) < 46.8 (erg per sec) and cover the full range of starburst galaxy and AGN classifications. Obtaining these [CII] line fluxes with PACS will allow: 1. determining how precisely [CII] luminosity measures star formation rate by comparing to PAH features and emission lines that arise in starburst galaxies; 2. determining how [CII] luminosity and equivalent width changes with starburst/AGN fraction, by comparing with strength and equivalent width of PAH and [NeII] emission arising from starbursts, and with strength of high ionization lines [NeV] and [OIV] and silicate absorption or emission arising from AGN; 3. determining how [CII] luminosity and equivalent width changes with dust temperature and bolometric luminosity, as derived from spectral energy distributions, and whether this depends on the starburst/AGN fraction. These determinations will allow interpretation of high redshift sources for which the only available diagnostics are the luminosity and equivalent width of the [CII] line and the far-infrared rest-frame SED. The total observing program requires 20.2 hours of Herschel observing time.

  18. Improved characterization of intranight optical variability of prominent AGN classes

    NASA Astrophysics Data System (ADS)

    Goyal, Arti; Gopal-Krishna, Wiita, Paul J.; Stalin, C. S.; Sagar, Ram

    2013-10-01

    The incidence of intranight optical variability (INOV) is known to differ significantly among different classes of powerful active galactic nuclei (AGN). A number of statistical methods have been employed in the literature for testing the presence of INOV in the light curves, sometimes leading to discordant results. In this paper, we compare the INOV characteristics of six prominent classes of AGN, as evaluated using three commonly used statistical tests, namely the χ2-test, the modified C-test and the F-test, which has recently begun to gain popularity. The AGN classes considered are: radio-quiet quasars, radio-intermediate quasars, lobe-dominated quasars, low optical polarization core-dominated quasars, high optical polarization core-dominated quasars and TeV blazars. Our analysis is based on a large body of AGN monitoring data, involving 262 sessions of intranight monitoring of a total 77 AGN, using 1-2 m class optical telescopes located in India. In order to compare the usefulness of the statistical tests, we have also subjected them to a `sanity check' by comparing the number of false positives yielded by each test with the corresponding statistical prediction. The present analysis is intended to serve as a benchmark for future INOV studies of AGN of different classes.

  19. Mini-Survey Of SDSS of [OIII] AGN With Swift

    NASA Technical Reports Server (NTRS)

    Angelini, L.; George, I. M.; Hill, J.; Padgett, C. A.; Mushotzky, R. F.

    2008-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

  20. YOUNG AGN OUTBURST RUNNING OVER OLDER X-RAY CAVITIES

    SciTech Connect

    Bogdán, Ákos; Van Weeren, Reinout J.; Kraft, Ralph P.; Forman, William R.; Randall, Scott; Jones, Christine; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher P.; Baum, Stefi A.; Noell-Storr, Jacob

    2014-02-20

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193—a nearby lenticular galaxy—based on X-ray (Chandra) and radio (Very Large Array and Giant Meter-wave Radio Telescope) observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced ∼78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  1. Young AGN Outburst Running over Older X-Ray Cavities

    NASA Astrophysics Data System (ADS)

    Bogdan, Akos; van Weeren, Reinout Johannes; Kraft, Ralph; Forman, William; Scott, Randall; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher; Baum, Stefi; Noell-Storr, Jacob; Jones, Christine

    2015-08-01

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193 -- a nearby lenticular galaxy in a group -- based on X-ray and radio observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced about 78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  2. Unwrapping the X-ray Spectra of AGN

    NASA Astrophysics Data System (ADS)

    Reynolds, C.

    2015-07-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around the spinning supermassive black hole with a compact, probably pair-regulated, X-ray corona. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds (and sometimes jets) are seen and can dominate the source energetics. As I shall review in this talk, each of these components imprints its own characteristic signature into the (time-variable) X-ray spectrum of the AGN. I shall then touch upon a few contemporary topics : (i) the use of new spectral timing techniques for aiding in the decomposition of the spectrum and for probing the geometry of the AGN central engine, (ii) the determination of supermassive black hole spin, (iii) direct confirmation of quasar-mode feedback in some luminous systems. The prospect of AGN observations with Astro-H will be discussed.

  3. Obscured AGNs in Bulgeless Hosts discovered by WISE: The Case Study of SDSS J1224+5555

    NASA Astrophysics Data System (ADS)

    Satyapal, S.; Secrest, N. J.; Rothberg, B.; O'Connor, J. A.; Ellison, S. L.; Hickox, R. C.; Constantin, A.; Gliozzi, M.; Rosenberg, J. L.

    2016-08-01

    There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of {L}2-10{keV}=(1.1+/- 0.4)× {10}40 erg s-1. Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of {N}{{H}}\\gt {10}24 cm-2. The hard X-ray luminosity of the putative AGN corrected for absorption is {L}2-10{keV}˜ 3× {10}42 erg s-1, which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of {L}{bol}.˜ 6× {10}43-3 × 1044 {erg} {{{s}}}-1 and a lower mass limit for the black hole of {M}{BH}≃ 2× {10}6 {M}⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ˜ 2.0× {10}10 {M}⊙ and an above solar metallicity (12 + {logO}/{{H}} = 9.11), typical of our WISE-selected bulgeless galaxy sample. While collectively these

  4. Properties and evolution of radio-AGN hosts since z~4

    NASA Astrophysics Data System (ADS)

    Delvecchio, Ivan

    2016-08-01

    We analyse the multi-wavelength properties of about 6200 radio (3-GHz) selected sources in the COSMOS field to investigate the impact of AGN activity on the integrated properties of their hosts. Two main classes of AGN are identified: radiatively-efficient AGN, by combining X-ray, mid-IR diagnostics and SED decomposition, and radiatively-inefficient AGN, that show up only in radio. Interestingly, we find significantly distinct galaxy properties for the two AGN classes, as a function of redshift. At z<2, radiatively-inefficient AGN are typically found in more massive and less star-forming galaxies than radiatively-efficient AGN, while at higher redshift we observe a possible reversal of their stellar mass distributions. We interpret these trends in the context of the anti-hierarchical growth of AGN host galaxies, with a particular focus on the role of AGN feedback over cosmic time in radio-selected samples.

  5. Properties And Evolution Of Radio-AGN Hosts Since z ~ 4

    NASA Astrophysics Data System (ADS)

    Delvecchio, Ivan; Smolčić, V.; Zamorani, G.; Del P. Lagos, C.; Berta, S.; Delhaize, J.; Baran, N.; Alexander, D.; Rosario, D.; et al.

    2016-10-01

    We analyse the multi-wavelength properties of about 7500 radio (3-GHz) selected sources in the COSMOS field to investigate the impact of AGN activity on the integrated properties of their hosts. Two main classes of AGN are identified: radiatively- efficient AGN, by combining X-ray, mid-IR diagnostics and SED decomposition, and radiatively-inefficient AGN, that show up only in radio. Interestingly, we find significantly distinct galaxy properties for the two AGN classes, as a function of redshift. At z<1.5, radiatively-inefficient AGN are typically found in more massive and less star-forming galaxies than radiatively-efficient AGN, while at higher redshift we observe a possible reversal of their stellar mass distributions. We interpret these trends in the context of the anti-hierarchical growth of AGN host galaxies, with a particular focus on the role of AGN feedback over cosmic time in radio-selected samples.

  6. Hiding in plain sight - recovering clusters of galaxies with the strongest AGN in their cores

    NASA Astrophysics Data System (ADS)

    Green, T. S.; Edge, A. C.; Ebeling, H.; Burgett, W. S.; Draper, P. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Wainscoat, R. J.; Waters, C.

    2017-03-01

    A key challenge in understanding the feedback mechanism of active galactic nucleus (AGN) in Brightest Cluster Galaxies (BCGs) is the inherent rarity of catching an AGN during its strong outburst phase. This is exacerbated by the ambiguity of differentiating between AGN and clusters in X-ray observations. If there is evidence for an AGN then the X-ray emission is commonly assumed to be dominated by the AGN emission, introducing a selection effect against the detection of AGN in BCGs. In order to recover these 'missing' clusters, we systematically investigate the colour-magnitude relation around some ∼3500 ROSAT All-Sky Survey selected AGN, looking for signs of a cluster red sequence. Amongst our 22 candidate systems, we independently rediscover several confirmed systems, where a strong AGN resides in a central galaxy. We compare the X-ray luminosity to red sequence richness distribution of our AGN candidate systems with that of a similarly selected comparison sample of ∼1000 confirmed clusters and identify seven 'best' candidates (all of which are BL Lac objects), where the X-ray flux is likely to be a comparable mix between cluster and AGN emission. We confirm that the colours of the red sequence are consistent with the redshift of the AGN, that the colours of the AGN host galaxy are consistent with AGN, and, by comparing their luminosities with those from our comparison clusters, confirm that the AGN hosts are consistent with BCGs.

  7. Particle acceleration in rotating and shearing jets from AGN

    NASA Astrophysics Data System (ADS)

    Rieger, F. M.; Mannheim, K.

    2002-12-01

    We model the acceleration of energetic particles due to shear and centrifugal effects in rotating astrophysical jets. The appropriate equation describing the diffusive transport of energetic particles in a collisionless, rotating background flow is derived and analytical steady state solutions are discussed. In particular, by considering velocity profiles from rigid, over flat to Keplerian rotation, the effects of centrifugal and shear acceleration of particles scattered by magnetic inhomogeneities are distinguished. In the case where shear acceleration dominates, it is confirmed that power law particle momentum solutions f(p) ~ p-(3+alpha ) exist, if the mean scattering time tauc ~ palpha is an increasing function of momentum. We show that for a more complex interplay between shear and centrifugal acceleration, the recovered power law momentum spectra might be significantly steeper but flatten with increasing azimuthal velocity due to the increasing centrifugal effects. The possible relevance of shear and centrifugal acceleration for the observed extended emission in AGN is demonstrated for the case of the jet in the quasar 3C273.

  8. Extending ROSAT Light Curves of Ecliptic Pole AGN Formation and Galaxy Evolution

    NASA Technical Reports Server (NTRS)

    Malkan, Matthew A.

    1997-01-01

    In collaboration with UCLA graduate student Fred Baganoff, Professor Malkan has obtained the longest continuous light curves ever available for a large sample (# = 60) of active galactic nuclei. This was accomplished by using the ROSATAII-Sky Survey, which covered the ecliptic pole regions once every 9O-minute orbit. Using this Astrophysics Data Processing grant from NASA, we extended these light curves by combining the RASS data with pointed observations over the next several years of operation of the ROSAT PSPC. This lengthens the baselines of about half of the light curves from a few months up to a few years. The proportion of AGN showing variability increases substantially with this improvement. In fact most AGN in this representative sample are now shown to be significantly variable in the X-rays. We are also able to say something about the amplitudes of variability on timescales from days to years, with more detail than previously has been possible. We have also identified some dependence of the X-ray variability properties on a) the luminosity of the AGN; and b) The presence of a "Blazar" nucleus. By extending the ROSAT light curves, we are also able to learn more about the correlation of X-ray and optical emission on longer time-scales. It appears to be very weak, at best.

  9. SUPERNOVAE AND AGN DRIVEN GALACTIC OUTFLOWS

    SciTech Connect

    Sharma, Mahavir; Nath, Biman B. E-mail: biman@rri.res.in

    2013-01-20

    We present analytical solutions for winds from galaxies with a Navarro-Frank-White (NFW) dark matter halo. We consider winds driven by energy and mass injection from multiple supernovae (SNe), as well as momentum injection due to radiation from a central black hole. We find that the wind dynamics depends on three velocity scales: (1) v{sub *}{approx}( E-dot / 2 M-dot ){sup 1/2} describes the effect of starburst activity, with E-dot and M-dot as energy and mass injection rate in a central region of radius R; (2) v {sub .} {approx} (GM {sub .}/2R){sup 1/2} for the effect of a central black hole of mass M {sub .} on gas at distance R; and (3) v{sub s}=(GM{sub h} / 2Cr{sub s}){sup 1/2}, which is closely related to the circular speed (v{sub c} ) for an NFW halo, where r{sub s} is the halo scale radius and C is a function of the halo concentration parameter. Our generalized formalism, in which we treat both energy and momentum injection from starbursts and radiation from the central active galactic nucleus (AGN), allows us to estimate the wind terminal speed to be (4v {sup 2} {sub *} + 6({Gamma} - 1)v {sub .} {sup 2} - 4v {sup 2} {sub s}){sup 1/2}, where {Gamma} is the ratio of force due to radiation pressure to gravity of the central black hole. Our dynamical model also predicts the following: (1) winds from quiescent star-forming galaxies cannot escape from 10{sup 11.5} M {sub Sun} {<=} M{sub h} {<=} 10{sup 12.5} M {sub Sun} galaxies; (2) circumgalactic gas at large distances from galaxies should be present for galaxies in this mass range; (3) for an escaping wind, the wind speed in low- to intermediate-mass galaxies is {approx}400-1000 km s{sup -1}, consistent with observed X-ray temperatures; and (4) winds from massive galaxies with AGNs at Eddington limit have speeds {approx}> 1000 km s{sup -1}. We also find that the ratio [2v {sup 2} {sub *} - (1 - {Gamma})v {sub .} {sup 2}]/v {sup 2} {sub c} dictates the amount of gas lost through winds. Used in conjunction with

  10. Mini Survey of SDSS [OIII] AGN with Swift: Testing the Hypothesis that L(sub [OIII]) Traces AGN Luminosity

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work strongly suggests every massive galaxy has a central black hole. However most of these objects either are not radiating or have been very difficult to detect We are now in the era of large surveys, and the luminosity function (LF] of AGN has been estimated in various ways. In the X-ray band. Chandra and XMM surveys have revealed that the LF of hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(sub x) (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects. If as been suggested, hard X ray and optical emission line can both can be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

  11. VizieR Online Data Catalog: Suzaku view of highly ionized outflows in AGN (Gofford+, 2013)

    NASA Astrophysics Data System (ADS)

    Gofford, J.; Reeves, J. N.; Tombesi, F.; Braito, V.; Turner, T. J.; Miller, L.; Cappi, M.

    2014-03-01

    We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for FeXXV Heα and/or FeXXVI Lyα absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E>~6.7keV in 20/51 sources at the PMC>=95% level, which corresponds to ~40% of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to FeXXV Heα and FeXXVI Lyα at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the FeK absorption components are log(NH/cm2)~23 and log({xi}/erg/cm/s)~4.5, respectively. Measured outflow velocities span a continuous range from <1500km/s up to ~100000km/s, with mean and median values of ~0.1c and ~0.056c, respectively. The results of this work are consistent with those recently obtained using XMM-Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe. (2 data files).

  12. The Suzaku View of Highly Ionized Outflows in AGN. 1; Statistical Detection and Global Absorber Properties

    NASA Technical Reports Server (NTRS)

    Gofford, Jason; Reeves, James N.; Tombesi, Francesco; Braito, Valentina; Turner, T. Jane; Miller, Lance; Cappi, Massimo

    2013-01-01

    We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for Fe XXV Healpha and/or Fe XXVI Lyalpha absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E greater than or approximately equal to 6.7 keV in 20/51 sources at the P(sub MC) greater than or equal tov 95 per cent level, which corresponds to approximately 40 per cent of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to Fe XXV Healpha and Fe XXVI Lyalpha at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the Fe K absorption components are log (N(sub H) per square centimeter)) is approximately equal to 23 and log (Xi/erg centimeter per second) is approximately equal to 4.5, respectively. Measured outflow velocities span a continuous range from less than1500 kilometers per second up to approximately100 000 kilometers per second, with mean and median values of approximately 0.1 c and approximately 0.056 c, respectively. The results of this work are consistent with those recently obtained using XMM-Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe.

  13. BLACK HOLE MASS AND EDDINGTON RATIO DISTRIBUTION FUNCTIONS OF X-RAY-SELECTED BROAD-LINE AGNs AT z {approx} 1.4 IN THE SUBARU XMM-NEWTON DEEP FIELD

    SciTech Connect

    Nobuta, K.; Akiyama, M.; Ueda, Y.; Hiroi, K.; Ohta, K.; Iwamuro, F.; Yabe, K.; Moritani, Y.; Sumiyoshi, M.; Maihara, T.; Watson, M. G.; Silverman, J.; Tamura, N.; Kimura, M.; Takato, N.; Dalton, G.; Lewis, I.; Bonfield, D.; Lee, H.; Curtis-Lake, E.; and others

    2012-12-20

    In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z {approx} 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 A monochromatic luminosity. We supplement the Mg II FWHM values with the H{alpha} FWHM obtained from our NIR spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V{sub max} method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF at z = 1.4 has a higher number density above 10{sup 8} M{sub Sun} but a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.

  14. Understanding Multiplication of Fractions.

    ERIC Educational Resources Information Center

    Sweetland, Robert D.

    1984-01-01

    Discussed the use of Cuisenaire rods in teaching the multiplication of fractions. Considers whole number times proper fraction, proper fraction multiplied by proper fraction, mixed number times proper fraction, and mixed fraction multiplied by mixed fractions. (JN)

  15. Spectropolarimetry of AGN, and `Women &\\ Science'

    NASA Astrophysics Data System (ADS)

    Kay, L.

    1999-12-01

    I have been using optical spectropolarimetry to investigate the nature of AGN. For the CAREER project, I have worked with A. M. Magalhães of the IAG in Brazil to use a visiting polarimetry module with the RC Spectrograph at CTIO, as well as conduct observations at Lick. Projects include observations of broad--line radio galaxies with double--peaked emission line profiles suggestive of accretion disks, and observations of a sample of X-ray selected narrow--line Seyfert 1 galaxies. Another project involves optical and X-ray observations of a complete sample of nearby Seyfert 2 galaxies in order to investigate the frequency of obscured broad--line regions and to determine their contribution to the X-ray background. In addition to involving undergraduate students in research, my educational efforts have focused on getting science into our Women's Studies program. I teach a course on the history and sociology of women in science, co-teach a course on feminist science studies, helped to create a course on women's health, organized a faculty seminar on gender and science issues, and lead a project at Barnard on gender and scientific literacy. I gratefully acknowledge support from NSF CAREER grant AST-9501835, as well as support from NSF International Research Fellowship INT-9423970, and from NSF grant EHR-9555808 to the AAC&U for the Gender and Scientific Literacy project.

  16. Optically faint radio sources: reborn AGN?

    NASA Astrophysics Data System (ADS)

    Filho, M. E.; Brinchmann, J.; Lobo, C.; Antón, S.

    2011-12-01

    We present our discovery of several relatively strong radio sources in the field-of-view of SDSS galaxy clusters that have no optical counterparts down to the magnitude limits of the SDSS. The optically faint radio sources appear as double-lobed or core-jet objects in the FIRST radio images and have projected angular sizes ranging from 0.5 to 1.0 arcmin. We followed-up these sources with near-infrared imaging using the wide-field imager HAWK-I on the VLT. We detected Ks-band emitting regions, about 1.5 arcsec in size and coincident with the centers of the radio structures, in all sources, with magnitudes in the range 17-20 mag. We used spectral modelling to characterize the sample sources. In general, the radio properties are similar to those observed in 3CRR sources but the optical-radio slopes are consistent with those of moderate to high redshift (z < 4) gigahertz-peaked spectrum sources. Our results suggest that these unusual objects are galaxies whose black hole has been recently re-ignited but that retain large-scale radio structures, which are signatures of previous AGN activity.

  17. Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011

    NASA Astrophysics Data System (ADS)

    H. E. S. S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Arribas, M. Paz; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zabalza, V.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2014-03-01

    Context. About 40% of the observation time of the High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim of increasing the sample of known extragalactic very-high-energy (VHE, E > 100 GeV) sources and constraining the physical processes at play in potential emitters. Aims: H.E.S.S. observations of AGN, spanning a period from April 2004 to December 2011, are investigated to constrain their γ-ray fluxes. Only the 47 sources without significant excess detected at the position of the targets are presented. Methods: Upper limits on VHE fluxes of the targets were computed and a search for variability was performed on the nightly time scale. Results: For 41 objects, the flux upper limits we derived are the most constraining reported to date. These constraints at VHE are compared with the flux level expected from extrapolations of Fermi-LAT measurements in the two-year catalog of AGN. The H.E.S.S. upper limits are at least a factor of two lower than the extrapolated Fermi-LAT fluxes for 11 objects. Taking into account the attenuation by the extragalactic background light reduces the tension for all but two of them, suggesting intrinsic curvature in the high-energy spectra of these two AGN. Conclusions: Compilation efforts led by current VHE instruments are of critical importance for target-selection strategies before the advent of the Cherenkov Telescope Array (CTA).

  18. Characterizing the far-infrared properties of distant X-ray detected AGNs: evidence for evolution in the infrared-X-ray luminosity ratio

    NASA Astrophysics Data System (ADS)

    Mullaney, J. R.; Alexander, D. M.; Huynh, M.; Goulding, A. D.; Frayer, D.

    2010-01-01

    We investigate the far-infrared (FIR) properties of X-ray sources detected in the Chandra Deep Field-South (CDF-S) survey using the ultradeep 70 and 24 μm Spitzer observations taken in this field. Since only 30 (i.e. ~10 per cent) of the 266 X-ray sources in the region of the 70 μm observations are detected at 70 μm, we rely on stacking analyses of the 70 μm data to characterize the average 70 μm properties of the X-ray sources as a function of redshift, X-ray luminosity and X-ray absorption. Using Spitzer-IRS data of the Swift-Burst Alert Telescope (BAT) sample of z ~ 0 active galactic nuclei (AGNs), we show that the 70/24 μm flux ratio can distinguish between AGN-dominated and starburst-dominated systems out to z ~ 1.5. Among the X-ray sources detected at 70 μm, we note a large scatter in the observed 70/24 μm flux ratios, spanning almost a factor of 10 at similar redshifts, irrespective of object classification, suggesting a range of AGN:starburst ratios. From stacking analyses we find that the average observed 70/24 μm flux ratios of AGNs out to an average redshift of 1.5 are similar to z ~ 0 AGNs with similar X-ray luminosities (LX = 1042-44ergs-1) and absorbing column densities (NH <= 1023cm-2). Furthermore, both high-redshift and z ~ 0 AGNs follow the same tendency towards warmer 70/24 μm colours with increasing X-ray luminosity (LX). From analyses of the Swift-BAT sample of z ~ 0 AGNs, we note that the 70 μm flux can be used to determine the IR (8-1000 μm) luminosities of high-redshift AGNs. We use this information to show that LX = 1042-43ergs-1 AGNs at high redshifts (z = 1-2) have IR to X-ray luminosity ratios (LIR/LX) that are, on average, 4.7+10.2-2.0 and 12.7+7.1-2.6 times higher than AGNs with similar X-ray luminosities at z = 0.5-1 and ~0, respectively. By comparison, we find that the LIR/LX ratios of LX = 1043-44ergs-1 AGNs remain largely unchanged across this same redshift interval. We explore the consequences that these results may

  19. Accretion disk modeling of AGN continuum using non-LTE stellar atmospheres. [active galactic nuclei (AGN)

    NASA Technical Reports Server (NTRS)

    Sun, Wei-Hsin; Malkan, Matthew A.

    1988-01-01

    Active galactic nuclei (AGN) accretion disk spectra were calculated using non-LTE stellar atmosphere models for Kerr and Schwarzschild geometries. It is found that the Lyman limit absorption edge, probably the most conclusive observational evidence for the accretion disk, would be drastically distorted and displaced by the relativistic effects from the large gravitational field of the central black hole and strong Doppler motion of emitting material on the disk surface. These effects are especially pronounced in the Kerr geometry. The strength of the Lyman limit absorption is very sensitive to the surface gravity in the stellar atmosphere models used. For models at the same temperature but different surface gravities, the strength of the Lyman edge exhibits an almost exponential decrease as the surface gravity approach the Eddington limit, which should approximate the thin disk atmosphere. The relativistic effects as well as the vanishing of the Lyman edge at the Eddington gravity may be the reasons that not many Lyman edges in the rest frames of AGNs and quasars are found.

  20. AGN and Starbursts in Dusty Galaxy Mergers: Insights from the Great Observatories All-sky LIRG Survey

    NASA Astrophysics Data System (ADS)

    Mazzarella, Joseph M.

    2014-07-01

    The Great Observatories All-sky LIRG Survey (GOALS) is combining imaging and spectroscopic data from the Herschel, Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes augmented with extensive ground-based observations in a multiwavelength study of approximately 180 Luminous Infrared Galaxies (LIRGs) and 20 Ultraluminous Infrared Galaxies (ULIRGs) that comprise a statistically complete subset of the 60μm-selected IRAS Revised Bright Galaxy Sample. The objects span the full range of galaxy environments (giant isolated spirals, wide and close pairs, minor and major mergers, merger remnants) and nuclear activity types (Seyfert 1, Seyfert 2, LINER, starburst/HII), with proportions that depend strongly on the total infrared luminosity. I will review the science motivations and present highlights of recent results selected from over 25 peer-reviewed journal articles published recently by the GOALS Team. Statistical investigations include detection of high-ionization Fe K emission indicative of deeply embedded AGN, comparison of UV and far-IR properties, investigations of the fraction of extended emission as a function of wavelength derived from mid-IR spectroscopy, mid-IR spectral diagnostics and spectral energy distributions revealing the relative contributions of AGN and starbursts to powering the bolometric luminosity, and quantitative structure analyses that delineate the evolution of stellar bars and nuclear stellar cusps during the merger process. Multiwavelength dissections of individual systems have unveiled large populations of young star clusters and heavily obscured AGN in early-stage (II Zw 96), intermediate-stage (Mrk 266, Mrk 273), and late-stage (NGC 2623, IC 883) mergers. A recently published study that matches numerical simulations to the observed morphology and gas kinematics in mergers has placed four systems on a timeline spanning 175-260 million years after their first passages, and modeling of additional (U)LIRGs is underway. A very

  1. Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey

    NASA Astrophysics Data System (ADS)

    Chen, C.-T. J.; Brandt, W. N.; Reines, A. E.; Lansbury, G.; Stern, D.; Alexander, D. M.; Bauer, F.; Del Moro, A.; Gandhi, P.; Harrison, F. A.; Hickox, R. C.; Koss, M. J.; Lanz, L.; Luo, B.; Mullaney, J. R.; Ricci, C.; Trump, J. R.

    2017-03-01

    We present a sample of 10 low-mass active galactic nuclei (AGNs) selected from the 40-month Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The sample is selected to have robust NuSTAR detections at 3{--}24 {keV}, to be at z< 0.3, and to have optical r-band magnitudes at least 0.5 mag fainter than an {L}\\star galaxy at its redshift. The median values of absolute magnitude, stellar mass, and 2–10 X-ray luminosity of our sample are < {M}r> =-20.03, < {M}\\star > =4.6× {10}9 {M}ȯ , and < {L}2-10{keV}> =3.1× {10}42 erg s‑1, respectively. Five objects have detectable broad Hα emission in their optical spectra, indicating black hole masses of (1.1{--}10.4)× {10}6 {M}ȯ . We find that {30}-10+17 % of the galaxies in our sample do not show AGN-like optical narrow emission lines, and one of the 10 galaxies in our sample, J115851+4243.2, shows evidence for heavy X-ray absorption. This result implies that a non-negligible fraction of low-mass galaxies might harbor accreting massive black holes that are missed by optical spectroscopic surveys and < 10 {keV} X-ray surveys. The mid-IR colors of our sample also indicate that these optically normal low-mass AGNs cannot be efficiently identified with typical AGN selection criteria based on Wide Field Infrared Survey Explorer colors. While the hard (> 10 keV) X-ray-selected low-mass AGN sample size is still limited, our results show that sensitive NuSTAR observations are capable of probing faint hard X-ray emission originating from the nuclei of low-mass galaxies out to moderate redshift (z< 0.3), thus providing a critical step in understanding AGN demographics in low-mass galaxies.

  2. Average Heating Rate of Hot Atmospheres in Distant Galaxy Clusters by Radio AGN: Evidence for Continuous AGN Heating

    NASA Astrophysics Data System (ADS)

    Ma, Cheng-Jiun; McNamara, B.; Nulsen, P.; Schaffer, R.

    2011-09-01

    X-ray observations of nearby clusters and galaxies have shown that energetic feedback from AGN is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 -- 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in 400SD, but cannot rule out the presence of weak cooling flows. The average jet power of central radio AGN is approximately 2 10^{44} erg/s. The jet power corresponds to an average heating of approximately 0.2 keV/particle for gas within R_500. Assuming the current AGN heating rate remained constant out to redshifts of about 2, these figures would rise by a factor of two. Our results show that the integrated energy injected from radio AGN outbursts in clusters is statistically significant compared to the excess entropy in hot atmospheres that is required for the breaking of self-similarity in cluster scaling relations. It is not clear that central AGN in 400SD clusters are maintained by a self-regulated feedback loop at the base of a cooling flow. However, they may play a significant role in preventing the development of strong cooling flows at early epochs.

  3. CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE AGNs. I. SPECTROSCOPIC PROPERTIES AND SERENDIPITOUS DISCOVERY OF NEW DUAL AGNs

    SciTech Connect

    Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni; Jimenez-Bailon, Elena; Mendez-Abreu, Jairo; Lopez-Martin, Luis; Fuentes-Carrera, Isaura; Leon-Tavares, Jonathan; Chavushyan, Vahram H.

    2013-01-20

    A sample of 10 nearby intermediate-type active galactic nuclei (AGNs) drawn from the Sloan Digital Sky Survey is presented. The aim of this work is to provide estimations of the black hole (BH) mass for the sample galaxies from the dynamics of the broad-line region. For this purpose, a detailed spectroscopic analysis of the objects was done. Using Baldwin-Phillips-Terlevich diagnostic diagrams, we have carefully classified the objects as true intermediate-type AGNs and found that 80%{sup +7.2%} {sub -17.3%} are composite AGNs. The BH mass estimated for the sample is within 6.54 {+-} 0.16 < log M {sub BH} < 7.81 {+-} 0.14. Profile analysis shows that five objects (J120655.63+501737.1, J121607.08+504930.0, J141238.14+391836.5, J143031.18+524225.8, and J162952.88+242638.3) have narrow double-peaked emission lines in both the red (H{alpha}, [N II] {lambda}{lambda}6548,6583 and [S II] {lambda}{lambda}6716, 6731) and the blue (H{beta} and [O III] {lambda}{lambda}4959, 5007) regions of the spectra, with velocity differences ({Delta}V) between the double peaks within 114 km s{sup -1} < {Delta}V < 256 km s{sup -1}. Two of them, J121607.08+504930.0 and J141238.14+391836.5, are candidates for dual AGNs since their double-peaked emission lines are dominated by AGN activity. In searches of dual AGNs, type 1, type II, and intermediate-type AGNs should be carefully separated, due to the high serendipitous number of narrow double-peaked sources (50% {+-} 14.4%) found in our sample.

  4. The Most Luminous Heavily Obscured Quasars Have a High Merger Fraction: Morphological Study of WISE-selected Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Fang, Guanwen; Gao, Ying; Zhang, Dandan; Jiang, Xiaoming; Wu, Qiaoqian; Yang, Jun; Li, Zhao

    2016-05-01

    Previous studies have shown that Wide-field Infrared Survey Explorer-selected hyperluminous, hot dust-obscured galaxies (Hot DOGs) are powered by highly dust-obscured, possibly Compton-thick active galactic nuclei (AGNs). High obscuration provides us a good chance to study the host morphology of the most luminous AGNs directly. We analyze the host morphology of 18 Hot DOGs at z ˜ 3 using Hubble Space Telescope/WFC3 imaging. We find that Hot DOGs have a high merger fraction (62 ± 14%). By fitting the surface brightness profiles, we find that the distribution of Sérsic indices in our Hot DOG sample peaks around 2, which suggests that most Hot DOGs have transforming morphologies. We also derive the AGN bolometric luminosity (˜1014 L ⊙) of our Hot DOG sample by using IR spectral energy distributions decomposition. The derived merger fraction and AGN bolometric luminosity relation is well consistent with the variability-based model prediction. Both the high merger fraction in an IR-luminous AGN sample and relatively low merger fraction in a UV/optical-selected, unobscured AGN sample can be expected in the merger-driven evolutionary model. Finally, we conclude that Hot DOGs are merger-driven and may represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst-dominated phase to the unobscured QSO phase.

  5. Interferometric IR observations: a diversity of dusty AGN tori

    NASA Astrophysics Data System (ADS)

    Burtscher, Leonard

    Interferometric observations in the infrared have resolved dusty structures on parsec and sub-parsec scales in more than two dozen AGNs by now -- a giant leap when considering that the first infrared interferometric observation of an extragalactic object is only about 10 years old. Since then, studies have confirmed the existence of dust in AGNs at its sublimation radius and have clearly dismissed models of very extended tori. Individual, well studied sources have been instrumental to reveal the complexity of these parsec-scale structures and statistical studies have shown a perplexing diversity in the population as a whole. Surprisingly, the diversity does not seem to follow the expected bimodality between optical type 1 and type 2 AGNs -- which are thought to be just face-on and edge-on tori. This central premise of viewing-angle dependent unified models is challenged if not dismissed by interferometric observations. The next step in understanding the AGN phenomenon -- beyond unification aspects -- is now to combine multi-scale observations with multi-scale simulations to constrain the physical processes driving the feeding and feedback of AGNs.

  6. Mini-Survey of SDSS OIII AGN with Swift

    NASA Technical Reports Server (NTRS)

    Angelina, Lorella; George, Ian

    2007-01-01

    There is a common wisdom that every massive galaxy has a massive block hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low Lx (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of (optically-selected samples) shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [OIII] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a mini-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([OIII]) to check the relation with the Lx observed with Swift.

  7. Inverse Compton X-ray signature of AGN feedback

    NASA Astrophysics Data System (ADS)

    Bourne, Martin A.; Nayakshin, Sergei

    2013-12-01

    Bright AGN frequently show ultrafast outflows (UFOs) with outflow velocities vout ˜ 0.1c. These outflows may be the source of AGN feedback on their host galaxies sought by galaxy formation modellers. The exact effect of the outflows on the ambient galaxy gas strongly depends on whether the shocked UFOs cool rapidly or not. This in turn depends on whether the shocked electrons share the same temperature as ions (one-temperature regime, 1T) or decouple (2T), as has been recently suggested. Here we calculate the inverse Compton spectrum emitted by such shocks, finding a broad feature potentially detectable either in mid-to-high energy X-rays (1T case) or only in the soft X-rays (2T). We argue that current observations of AGN do not seem to show evidence for the 1T component. The limits on the 2T emission are far weaker, and in fact it is possible that the observed soft X-ray excess of AGN is partially or fully due to the 2T shock emission. This suggests that UFOs are in the energy-driven regime outside the central few pc, and must pump considerable amounts of not only momentum but also energy into the ambient gas. We encourage X-ray observers to look for the inverse Compton components calculated here in order to constrain AGN feedback models further.

  8. Analyses of the Variability Asymmetry of Kepler AGNs

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Yang; Wang, Jun-Xian

    2015-05-01

    The high-quality light curves from the Kepler space telescope make it possible to analyze the optical variability of active galactic nuclei (AGNs) with unprecedented time resolution. Studying the asymmetry in variations could provide independent constraints on physical models for AGN variability. In this paper, we use Kepler observations of 19 sources to perform analyses of the variability asymmetry of AGNs. We apply smoothing correction to light curves to deduct their bias toward high-frequency variability asymmetry caused by long-term variations that have been poorly sampled due to the limited length of light curves. A parameter β based on structure functions is introduced to quantitively describe the asymmetry and its uncertainty is measured using extensive Monte Carlo simulations. Individual sources show no evidence of asymmetry at timescales of 1˜ 20 days and there is no general trend toward positive or negative asymmetry over the whole sample. Stacking the data from all 19 AGNs, we derive an averaged \\bar{β } of 0.00 ± 0.03 and -0.02 ± 0.04 over timescales of 1 ˜ 5 days and 5 ˜ 20 days, respectively, which are statistically consistent with zero. Quasars and Seyfert galaxies show similar asymmetry parameters. Our results indicate that short-term optical variations in AGNs are highly symmetric.

  9. Mid-infrared Flux Variability in an Awakening AGN

    NASA Astrophysics Data System (ADS)

    Yeh, Sherry

    We propose FORCAST spectroscopic observations between 8 um to 40 um near the nucleus of NGC 660. NGC 660 underwent an AGN outburst 6 years ago, which is an ideal case for studying AGN astrophysics in a rather quiecent system. However, this rare event has not yet been monitored. Our immidiate goal is to verify the MIR spectroscipic variabilitiy in NGC 660, and to study the AGN effects on dust destruction and ISM. We will compare the FORCAST spectra with the Spitzer IRS spectra (taken before the AGN outburst), including dust continuum, PAH emission, and high- and low-ionization emission lines. FORCAST's slit width is a close match to the IRS slit width, allowing a direct comparison of the spectra between FORCAST and IRS. Our single-slit Subaru COMICS spectrum taken after the outburst shows significantly weakened PAH emission and dust continuum, suggesting dust destruction. However, it is difficult to draw robust intepretations due to systematic uncertainties in the Subaru data. If dust destruction is confirmed in the post-outburst FORCAST observaitons, we will evaluate the energy budget using the MIR line ratio diagnostics, with archival X-ray and radio data. We will then propose cadence observations of MGC 660's nucleus to monitor the MIR flux variability, and employ the reverberation mapping technique to study NGC 660's AGN.

  10. Pan-STARRS1 variability of XMM-COSMOS AGN. I. Impact on photometric redshifts

    NASA Astrophysics Data System (ADS)

    Simm, T.; Saglia, R.; Salvato, M.; Bender, R.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Tonry, J. L.; Wainscoat, R. J.; Waters, C.

    2015-12-01

    Aims: Upcoming large area sky surveys like Euclid and eROSITA, which are dedicated to studying the role of dark energy in the expansion history of the Universe and the three-dimensional mass distribution of matter, crucially depend on accurate photometric redshifts. The identification of variable sources, such as active galactic nuclei (AGNs), and the achievable redshift accuracy for varying objects are important in view of the science goals of the Euclid and eROSITA missions. Methods: We probe AGN optical variability for a large sample of X-ray-selected AGNs in the XMM-COSMOS field, using the multi-epoch light curves provided by the Pan-STARRS1 (PS1) 3π and Medium Deep Field surveys. To quantify variability we employed a simple statistic to estimate the probability of variability and the normalized excess variance to measure the variability amplitude. Utilizing these two variability parameters, we defined a sample of varying AGNs for every PS1 band. We investigated the influence of variability on the calculation of photometric redshifts by applying three different input photometry sets for our fitting procedure. For each of the five PS1 bands gP1, rP1, iP1, zP1, and yP1, we chose either the epochs minimizing the interval in observing time, the median magnitude values, or randomly drawn light curve points to compute the redshift. In addition, we derived photometric redshifts using PS1 photometry extended by GALEX/IRAC bands. Results: We find that the photometry produced by the 3π survey is sufficient to reliably detect variable sources provided that the fractional variability amplitude is at least ~3%. Considering the photometric redshifts of variable AGNs, we observe that minimizing the time spacing of the chosen points yields superior photometric redshifts in terms of the percentage of outliers (33%) and accuracy (0.07), outperforming the other two approaches. Drawing random points from the light curve gives rise to typically 57% of outliers and an accuracy of

  11. Mystery Fractions

    ERIC Educational Resources Information Center

    Bhattacharyya, Sonalee; Namakshi, Nama; Zunker, Christina; Warshauer, Hiroko K.; Warshauer, Max

    2016-01-01

    Making math more engaging for students is a challenge that every teacher faces on a daily basis. These authors write that they are constantly searching for rich problem-solving tasks that cover the necessary content, develop critical-thinking skills, and engage student interest. The Mystery Fraction activity provided here focuses on a key number…

  12. Pitch Fractionation.

    DTIC Science & Technology

    1981-12-15

    13 3. Solvent Fractionation Experiments .................................... 15 4. Fourier Transform Infrared Spectra for A240 Petrolem Pitch AG 12...34 and Mesophase Pitch AG 164B ............................... 21 5. Fourier Transform Infrared Spectra ................................... 23 6...compared by Fourier transform infrared (FTIR) analysis using a Digilab Model FTS 14 spectrophotometer (Rockwell International, Anaheim, California

  13. Circular Polarization in AGNs: Polarity and Spectra

    NASA Astrophysics Data System (ADS)

    Aller, M. F.; Aller, H. D.; Plotkin, R. M.

    2005-12-01

    Circular polarization (Stokes V) observations potentially provide information on the nature and origin of the underlying magnetic fields in AGNs. We have been systematically monitoring a group of sources with detectable circular polarization (V>0.1 percent, a level set by the instrumental polarization of our system) in all 4 Stokes parameters at 8.0 and 4.8 GHz since 2000, and also at 14.5 GHz since November 2003, with the University of Michigan prime focus paraboloid antenna. These data are compared with historical observations obtained with the same instrument at 8.0 and 4.8 GHz extending back to 1978. Specific goals are to study the temporal spectral behavior of Stokes V and its relation to variability in total flux and linear polarization, and to investigate the question of polarity stability on decade-long time scales using data obtained with the same instrumentation and at the same frequencies. The data are consistent with linear-to-circular mode conversion in partially opaque regions of the source. We find examples of polarity changes with time at one or more frequencies associated with outbursts in total flux and linear polarization, and polarity differences within the 3 frequencies at a single epoch in one case, 3C 279. Such behavior argues against the notion that the sign of Stokes V is a simple tracer of the net flow of magnetic energy from the central engine to the jet or an indicator of the direction of rotation of the spinning central black hole/accretion disk via the winding up of the initial seed magnetic field. This work was supported in part by NSF grant AST-0307629 and by funds from the University of Michigan.

  14. Agnes Pockels: Life, Letters and Papers

    NASA Astrophysics Data System (ADS)

    Helm, Christiane A.

    2004-03-01

    Agnes Pockels (1862 - 1935) was a German woman, whose studies pioneered surface science. She was born in malaria infected North Italy while her father served in the Austrian army. Because he suffered adverse health effects, the family moved in1871 to Braunschweig (North Germany). There, Pockels went to high school. She was interested in science, but formal training was not available for girls. She took on the role of household manager and nurse as her parents' health deteriorated further. Her diary illustrates the difficulties she faced in trying to maintain her own health, the health of her parents and her scientific research at the same time. When Pockels was 18 or 19, she designed a ring tensiometer. Additionally, she found a new method to introduce water-insoluble compounds to the water surface by dissolving them in an organic solvent, and applying drops of the solution. Her surface film balance technique from 1882 is the basis for the method later developed by Langmuir. Since her experimental work was highly original and in a new field, she failed to get it recognized in her own country. When she was 28, she wrote to Lord Rayleigh, since she had read about his recent experiments in surface physics. Rayleigh was so impressed with her experimental methods and results that he had her letter translated from German and published it in Nature (1891). She continued her research on surface films, interactions of solutions and contact angles (more papers, 3 in Nature). Still, she did all experiments at home. With the death of her brother in 1913 and the onset of the war, she retired into private life. Thus she was surprised when she was awarded in her late 60ies with a honorary doctorate by the TU Braunschweig (1932) and the annual prize of the German Colloid Society (1931).

  15. AGN variability in the radio band

    NASA Astrophysics Data System (ADS)

    Max-Moerbeck, Walter

    2016-08-01

    Variability is an important and defining characteristic of AGN, that along with their broadband spectral energy distribution make their study interesting and challenging. A complete understanding of the physics of these objects requires monitoring observations over the whole electromagnetic spectrum, and includes studying their properties at a given band and also the relationship between multiple wavelengths. Here we present the main results obtained so far with the ongoing OVRO 40m blazar monitoring program at 15 GHz with twice a week cadence. This program started in mid-2007 and is currently monitoring about 1800 blazars, including most of the bright blazars north of declination -20 degrees. These results include: characterization of the variability in the radio band; its relationship with optical and gamma-ray properties; and its relationship to gamma-ray emission as observed with Fermi-LAT, which can provide constrains on the location of the gamma-ray emission region. We will also discuss our ongoing work on the characterization of radio variability using the power spectral density. For this, we are using 8 years of OVRO 40m data for ~1200 sources, and also F-GAMMA monitoring data taken with the Effelsberg 100m telescope for 60 sources with about monthly cadence monitoring data at 8 frequencies between 2.6 and 43.0 GHz. These studies will provide an improved understanding of blazar variability, a better basis to evaluate the statistics of correlated variability between different emission bands, and a long and consistent record of radio observations to be used in gamma-ray and multi-wavelength investigations.

  16. BAT AGN Spectroscopic Survey - III. An observed link between AGN Eddington ratio and narrow-emission-line ratios

    NASA Astrophysics Data System (ADS)

    Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D. Michael; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Soto, Kurt T.; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro

    2017-01-01

    We investigate the observed relationship between black hole mass (MBH), bolometric luminosity (Lbol) and Eddington ratio (λEdd) with optical emission-line ratios ([N II] λ6583/Hα, [S II] λλ6716, 6731/Hα, [O I] λ6300/Hα, [O III] λ5007/Hβ, [Ne III] λ3869/Hβ and He II λ4686/Hβ) of hard X-ray-selected active galactic nuclei (AGN) from the BAT AGN Spectroscopic Survey. We show that the [N II] λ6583/Hα ratio exhibits a significant correlation with λEdd (RPear = -0.44, p-value = 3 × 10-13, σ = 0.28 dex), and the correlation is not solely driven by MBH or Lbol. The observed correlation between [N II] λ6583/Hα ratio and MBH is stronger than the correlation with Lbol, but both are weaker than the λEdd correlation. This implies that the large-scale narrow lines of AGN host galaxies carry information about the accretion state of the AGN central engine. We propose that [N II] λ6583/Hα is a useful indicator of Eddington ratio with 0.6 dex of rms scatter, and that it can be used to measure λEdd and thus MBH from the measured Lbol, even for high-redshift obscured AGN. We briefly discuss possible physical mechanisms behind this correlation, such as the mass-metallicity relation, X-ray heating, and radiatively driven outflows.

  17. Disentangling AGN-Host Galaxy Interactions with Chandra

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng

    2014-11-01

    The circum-nuclear region in active galaxies is often complex with presence of high excitation gas, collimated radio outflow, and star forming regions, besides the active central supermassive black hole. In Chandra studies of a number of archetypal Seyfert galaxies to investigate AGN-host galaxy interaction, we were able to evaluate the mass outflow rate and shock heating by radio jet. For galaxies in the throes of a violent merging event such as NGC6240, we were able to resolve 70MK hot gas surrounding the double nuclei and discovered a large scale soft X-ray halo. The unique resolving power of Chandra also enables more discovery of such dual AGN systems and signs of past AGN outburst activities.

  18. Quenching histories of galaxies and the role of AGN feedback

    NASA Astrophysics Data System (ADS)

    Smethurst, Rebecca Jane; Lintott, Chris; Simmons, Brooke; Galaxy Zoo Team

    2016-01-01

    Two open issues in modern astrophysics are: (i) how do galaxies fully quench their star formation and (ii) how is this affected - or not - by AGN feedback? I present the results of a new Bayesian-MCMC analysis of the star formation histories of over 126,000 galaxies across the colour magnitude diagram showing that diverse quenching mechanisms are instrumental in the formation of the present day red sequence. Using classifications from Galaxy Zoo we show that the rate at which quenching can occur is morphologically dependent in each of the blue cloud, green valley and red sequence. We discuss the nature of these possible quenching mechanisms, considering the influence of secular evolution, galaxy interactions and mergers, both with and without black hole activity. We focus particularly on the relationship between these quenched star formation histories and the presence of an AGN by using this new Bayesian method to show a population of type 2 AGN host galaxies have recently (within 2 Gyr) undergone a rapid (τ < 1 Gyr) drop in their star formation rate. With this result we therefore present the first statistically supported observational evidence that AGN feedback is an important mechanism for the cessation of star formation in this population of galaxies. The diversity of this new method also highlights that such rapid quenching histories cannot account fully for all the quenching across the current AGN host population. We demonstrate that slower (τ > 2 Gyr) quenching rates dominate for high stellar mass (log10[M*/M⊙] > 10.75) hosts of AGN with both early- and late-type morphology. We discuss how these results show that both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes across the entirety of the colour magnitude diagram.

  19. AGN Survey to characterize the clumpy torus using FORCAST

    NASA Astrophysics Data System (ADS)

    Lopez-Rodriguez, Enrique

    2015-10-01

    A geometrically and optically thick torus of gas and dust obscures the black hole and accretion disk in active galactic nuclei (AGN) in some lines of sight. One of the most important question that still remain uncertain is: How do the properties, such as torus geometry and distribution of clumps, of the torus depend on the AGN luminosity and/or activity class? Infrared (IR) observations are essential to these investigations as the torus intercepts and re-radiates (peaking within 30-40 um) a substantial amount of flux from the central engine. Near-IR (NIR) and mid-IR (MIR) observations from the ground have been key to advance our knowledge in this field. However, the atmosphere is opaque to the 30-40 um range and observations are impossible from ground-based telescopes. FORCAST presents a unique opportunity to explore AGN, providing the best angular resolution observations within the 30-40 um range for the current suite of instruments. From our analysis using Cycle 2 observations, we found that FORCAST provides the largest constraining power of the clumpy torus models in the suggested wavelength range. We therefore request an AGN Survey using FORCAST of snapshot imaging observations of a flux-limited (>500 mJy at 37.1 um) sample of 23 Seyfert galaxies with existing high-angular resolution MIR spectra observed on 8-m class telescopes. Using the FORCAST data requested here in combination with already acquired NIR and MIR data, we will have an unprecedentedly homogeneous AGN sample of IR (1-40 um) SED at the largest spatial-resolution, which yield to a better knowledge of the torus structure in the AGN unified model.

  20. The most obscured AGN in the COSMOS field

    NASA Astrophysics Data System (ADS)

    Lanzuisi, G.; Perna, M.; Delvecchio, I.; Berta, S.; Brusa, M.; Cappelluti, N.; Comastri, A.; Gilli, R.; Gruppioni, C.; Mignoli, M.; Pozzi, F.; Vietri, G.; Vignali, C.; Zamorani, G.

    2015-06-01

    Highly obscured active galactic nuclei (AGN) are common in nearby galaxies, but are difficult to observe beyond the local Universe, where they are expected to significantly contribute to the black hole accretion rate density. Furthermore, Compton-thick (CT) absorbers (NH ≳ 1024 cm-2) suppress even the hard X-ray (2-10 keV) AGN nuclear emission, and therefore the column density distribution above 1024 cm-2 is largely unknown. We present the identification and multi-wavelength properties of a heavily obscured (NH ≳ 1025 cm-2), intrinsically luminous (L2-10 > 1044 erg s-1) AGN at z = 0.353 in the COSMOS field. Several independent indicators, such as the shape of the X-ray spectrum, the decomposition of the spectral energy distribution and X-ray/[NeV] and X-ray/6 μm luminosity ratios, agree on the fact that the nuclear emission must be suppressed by a ≳1025 cm-2 column density. The host galaxy properties show that this highly obscured AGN is hosted in a massive star-forming galaxy, showing a barred morphology, which is known to correlate with the presence of CT absorbers. Finally, asymmetric and blueshifted components in several optical high-ionization emission lines indicate the presence of a galactic outflow, possibly driven by the intense AGN activity (LBol/LEdd = 0.3-0.5). Such highly obscured, highly accreting AGN are intrinsically very rare at low redshift, whereas they are expected to be much more common at the peak of the star formation and BH accretion history, at z ~ 2-3. We demonstrate that a fully multi-wavelength approach can recover a sizable sample of such peculiar sources in large and deep surveys such as COSMOS.

  1. SPITZER MID-IR SPECTROSCOPY OF POWERFUL 2 JY AND 3CRR RADIO GALAXIES. I. EVIDENCE AGAINST A STRONG STARBURST-AGN CONNECTION IN RADIO-LOUD AGN

    SciTech Connect

    Dicken, D.; Axon, D.; Robinson, A.; Kharb, P.; Tadhunter, C.; Ramos Almeida, C.; Morganti, R.; Kouwenhoven, M. B. N.; Spoon, H.; Inskip, K. J.; Holt, J.; Nesvadba, N. P. H.

    2012-02-01

    We present deep Spitzer/Infrared Spectrograph (IRS) spectra for complete samples of 46 2 Jy radio galaxies (0.05 < z < 0.7) and 19 3CRR FRII radio galaxies (z < 0.1), and use the detection of polycyclic aromatic hydrocarbon (PAH) features to examine the incidence of contemporaneous star formation and radio-loud active galactic nucleus (AGN) activity. Our analysis reveals PAH features in only a minority (30%) of the objects with good IRS spectra. Using the wealth of complementary data available for the 2 Jy and 3CRR samples we make detailed comparisons between a range of star formation diagnostics: optical continuum spectroscopy, mid- to far-IR (MFIR) color, far-IR excess and PAH detection. There is good agreement between the various diagnostic techniques: most candidates identified to have star formation activity on the basis of PAH detection are also identified using at least two of the other techniques. We find that only 35% of the combined 2 Jy and 3CRR sample show evidence for recent star formation activity (RSFA) at optical and/or MFIR wavelengths. This result argues strongly against the idea of a close link between starburst and powerful radio-loud AGN activity, reinforcing the view that, although a large fraction of powerful radio galaxies may be triggered in galaxy interactions, only a minority are triggered at the peaks of star formation activity in major, gas-rich mergers. However, we find that compact radio sources (D < 15 kpc) show a significantly higher incidence of RSFA (>75%) than their more extended counterparts ( Almost-Equal-To 15%-25%). We discuss this result in the context of a possible bias toward the selection of compact radio sources triggered in gas-rich environments.

  2. The NuSTAR view of radio-quiet AGN

    NASA Astrophysics Data System (ADS)

    Marinucci, Andrea

    AUTHORS: A. Marinucci and the NuSTAR Team ABSTRACT: The Nuclear Spectroscopic Telescope Array (NuSTAR), thanks to its improved sensitivity in hard X-rays with respect to coded aperture observatories, is providing new and exciting results on radio-quiet AGN. In this talk I will present results from the NuSTAR AGN Physics program after the first two years of science operations. In particular, measurements of the black hole spin and coronal temperature in nearby sources will be discussed.

  3. Fraction Reduction through Continued Fractions

    ERIC Educational Resources Information Center

    Carley, Holly

    2011-01-01

    This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.

  4. Isotope fractionation

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    A rash of new controversy has emerged around the subject of mass-independent isotope fractionation effects, particularly in the case of the oxygen isotopes. To be sure, the controversy has been around for awhile, but it has been given new impetus by the results of a recent study by Mark H. Thiemens and John E. Heidenreich III of the University of California, San Diego (Science, March 4, 1983).Gustav Arrhenius has been trying to convince the planetary science community that chemical effects in isotope fractionation processes could explain observations in meteorites that appear to be outside of the traditionally understood mass-dependent fractionations (G. Arrhenius, J . L. McCrumb, and N. F. Friedman, Astrophys. Space Sci, 65, 297, 1974). Robert Clayton had made the basic observations of oxygen in carbonaceous chondrites that the slope of the δ17 versus δ18 line was 1 instead of the slope of ½ characteristic of terrestrial rocks and lunar samples (Ann. Rev. Nucl. Part. Sci., 28, 501, 1978). The mass-independent effects were ascribed to the apparent contribution of an ancient presolar system component of O16.

  5. High resolution VLBI polarization imaging of AGN with the maximum entropy method

    NASA Astrophysics Data System (ADS)

    Coughlan, Colm P.; Gabuzda, Denise C.

    2016-12-01

    Radio polarization images of the jets of Active Galactic Nuclei (AGN) can provide a deep insight into the launching and collimation mechanisms of relativistic jets. However, even at VLBI scales, resolution is often a limiting factor in the conclusions that can be drawn from observations. The maximum entropy method (MEM) is a deconvolution algorithm that can outperform the more common CLEAN algorithm in many cases, particularly when investigating structures present on scales comparable to or smaller than the nominal beam size with `super-resolution'. A new implementation of the MEM suitable for single- or multiple-wavelength VLBI polarization observations has been developed and is described here. Monte Carlo simulations comparing the performances of CLEAN and MEM at reconstructing the properties of model images are presented; these demonstrate the enhanced reliability of MEM over CLEAN when images of the fractional polarization and polarization angle are constructed using convolving beams that are appreciably smaller than the full CLEAN beam. The results of using this new MEM software to image VLBA observations of the AGN 0716+714 at six different wavelengths are presented, and compared to corresponding maps obtained with CLEAN. MEM and CLEAN maps of Stokes I, the polarized flux, the fractional polarization and the polarization angle are compared for convolving beams ranging from the full CLEAN beam down to a beam one-third of this size. MEM's ability to provide more trustworthy polarization imaging than a standard CLEAN-based deconvolution when convolving beams appreciably smaller than the full CLEAN beam are used is discussed.

  6. The MOSDEF Survey: AGN Multi-wavelength Identification, Selection Biases, and Host Galaxy Properties

    NASA Astrophysics Data System (ADS)

    Azadi, Mojegan; Coil, Alison L.; Aird, James; Reddy, Naveen; Shapley, Alice; Freeman, William R.; Kriek, Mariska; Leung, Gene C. K.; Mobasher, Bahram; Price, Sedona H.; Sanders, Ryan L.; Shivaei, Irene; Siana, Brian

    2017-01-01

    We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR, and optically selected active galactic nuclei (AGNs) at 1.4< z< 3.8. We obtain rest-frame optical spectra of galaxies and AGNs and use the BPT diagram to identify optical AGNs. We examine the uniqueness and overlap of the AGNs identified at different wavelengths. There is a strong bias against identifying AGNs at any wavelength in low-mass galaxies, and an additional bias against identifying IR AGNs in the most massive galaxies. AGN hosts span a wide range of star formation rates (SFRs), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at ∼2–3σ significance) that IR AGNs are in less dusty galaxies with relatively higher SFR and optical AGNs in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGNs in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGNs being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes.

  7. A Method of Identifying AGNs Based on Emission-Line Excess and the Nature of Low-Luminosity AGNs in the Sloan Digital Sky Survey. II. The Nature of Low-Luminosity AGNs

    NASA Astrophysics Data System (ADS)

    Tanaka, Masayuki

    2012-04-01

    We have developed a new method of identifying active galactic nuclei (AGNs) and studied the nature of low-luminosity AGNs in the Sloan Digital Sky Survey. This is the latter part of a series of papers in which we consider correlations between the AGN activities and the host-galaxy properties. Based on a sample of AGNs identified by a new method developed in the former part (2012, PASJ, 64, 36), we found that AGNs typically show extinction of τV = 1.2, and exhibit a wide range of ionization levels. The finding of ionization levels motivated us to use [O II] + [O III] as an indicator of AGN power. We found that AGNs are preferentially located in massive, red, early-type galaxies. Taking into account a selection bias of the Oxygen-excess method, we showed that strong AGNs are located in active star-forming galaxies, and that rapidly growing super-massive black holes are located in rapidly growing galaxies, which clearly shows the coevolution of super-massive black holes and their host galaxies. This is a surprising phenomenon, given that the growths of black holes and host galaxies occur on their respective physical scales which are very different. Interestingly, the AGN power does not strongly correlate with the host-galaxy mass. It seems that the mass works as a ``switch'' for activating AGNs. The absence of AGNs in low-mass galaxies might be due to the absence of super-massive black holes there, but a dedicated observation of the nuclear region of nearby low-mass galaxies would be necessary to obtain a deeper insight into it.

  8. Herschel FIR counterparts of selected Lyα emitters at z ~ 2.2. Fast evolution since z ~ 3 or missed obscured AGNs?

    NASA Astrophysics Data System (ADS)

    Bongiovanni, A.; Oteo, I.; Cepa, J.; Pérez García, A. M.; Sánchez-Portal, M.; Ederoclite, A.; Aguerri, J. A. L.; Alfaro, E. J.; Altieri, B.; Andreani, P.; Aparicio-Villegas, M. T.; Aussel, H.; Benítez, N.; Berta, S.; Broadhurst, T.; Cabrera-Caño, J.; Castander, F. J.; Cava, A.; Cerviño, M.; Chulani, H.; Cimatti, A.; Cristóbal-Hornillos, D.; Daddi, E.; Dominguez, H.; Elbaz, D.; Fernández-Soto, A.; Förster Schreiber, N.; Genzel, R.; Gómez, M. F.; González Delgado, R. M.; Grazian, A.; Gruppioni, C.; Herreros, J. M.; Iglesias Groth, S.; Infante, L.; Lutz, D.; Magnelli, B.; Magdis, G.; Maiolino, R.; Márquez, I.; Martínez, V. J.; Masegosa, J.; Moles, M.; Molino, A.; Nordon, R.; Del Olmo, A.; Perea, J.; Poglitsch, A.; Popesso, P.; Pozzi, F.; Prada, F.; Quintana, J. M.; Riguccini, L.; Rodighiero, G.; Saintonge, A.; Sánchez, S. F.; Santini, P.; Shao, L.; Sturm, E.; Tacconi, L.; Valtchanov, I.

    2010-09-01

    Lyα emitters (LAEs) are seen everywhere in the redshift domain from local to z ~ 7. Far-infrared (FIR) counterparts of LAEs at different epochs could provide direct clues on dust content, extinction, and spectral energy distribution (SED) for these galaxies. We search for FIR counterparts of LAEs that are optically detected in the GOODS-North field at redshift z ~ 2.2 using data from the Herschel Space Telescope with the Photodetector Array Camera and Spectrometer (PACS). The LAE candidates were isolated via color-magnitude diagram using the medium-band photometry from the ALHAMBRA Survey, ancillary data on GOODS-North, and stellar population models. According to the fitting of these spectral synthesis models and FIR/optical diagnostics, most of them seem to be obscured galaxies whose spectra are AGN-dominated. From the analysis of the optical data, we have observed a fraction of AGN or composite over source total number of ~0.75 in the LAE population at z ~ 2.2, which is marginally consistent with the fraction previously observed at z = 2.25 and even at low redshift (0.2 < z < 0.45), but significantly different from the one observed at redshift ~3, which could be compatible either with a scenario of rapid change in the AGN fraction between the epochs involved or with a non detection of obscured AGN in other z = 2-3 LAE samples due to lack of deep FIR observations. We found three robust FIR (PACS) counterparts at z ~ 2.2 in GOODS-North. This demonstrates the possibility of finding dust emission in LAEs even at higher redshifts. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices (pages 6 to 9) are only available in electronic form at http://www.aanda.org

  9. Review of Space VLBI RadioAstron studies of AGN

    NASA Astrophysics Data System (ADS)

    Gurvits, Leonid; Kovalev, Yuri

    2016-07-01

    Space VLBI offers an unrivalled resolution in studies of the AGN phenomena. Since 2011, the Russia-led SVLBI mission RadioAstron conducts observations at 92, 18, 6 and 1.3 cm with baselines an order of magnitude longer than the Earth diameter, therefore offering an order of magnitude "sharper" view at the brightest radio sources than achieved with Earth-based VLBI systems. In our presentation we will review the current status of the RadioAstron's scientific programme. Over the first 4.5 years of the in-orbit operations, the mission achieved successful VLBI detections of extragalactic continuum radio sources at all four observing bands. To date, detections on SVLBI baselines have been obtained for more than 150 AGN's at projected baselines up to 350 000 km (about 28 Earth diameters, ED). The highest resolution achieved is 14 microarcscends from 1.3 cm observations. RadioAstron is an international project; it conducts observations with up to 30 Earth-based radio telescopes located on different continents. We will review results of total intensity and polarisation imaging with extreme angular resolution of blazars and nearby active galaxies. We will also discuss typical and maximum brightness temperatures of blazar cores from the AGN Survey obtained with RadioAstron. Physical implications for the AGN jets formation, magnetic field and emission mechanism will be discussed on the basis of the results obtained to date.

  10. The Evolution of the AGN population in the MORGANA model

    NASA Astrophysics Data System (ADS)

    Fontanot, F.; Monaco, P.; Cristiani, S.; Tozzi, P.

    2008-10-01

    We present the results of the MOdel for the Rise of Galaxies aNd Agns (MORGANA), that includes in a self-consistent way the accretion of matter onto Super-Massive Black Holes. We compare MORGANA predictions to the observed evolution of the AGN space density (inferred from optical and X-ray surveys) and we find that that it is possible to reproduce the apparent downsizing of the AGN population in the framework of concordance cosmology. We will show that this result is likely due to the improved treatment of gas cooling and feedback in MORGANA, and in particular to the modeling of the stellar kinetic feedback, arising in star-forming bulges as a consequence of the level of turbolence. On the other hand, the predicted low-mass end of BH-bulge relation is steeper than observed: we discuss this disagreement on the light of the predicted excess of small bulges, which is common to several models of galaxy formation and evolution. Finally we will show that a stronger constrain on the relative importance of the physical processes involved in the build up of the AGN population move from the observed redshift evolution of the BH-Bulge relation.

  11. Fast Ionized X-ray Absorbers in AGNs

    NASA Astrophysics Data System (ADS)

    Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

    2015-07-01

    We present a study of X-ray ionization of MHD accretion-disk wind models in an effort to explain the highly-ionized ultra-fast outflows (UFOs) identified as X-ray absorbers recently detected in various sub-classes of Seyfert AGNs. Our primary focus is to show that magnetically-driven outflows are physically plausible candidates to account for the AGN X-ray spectroscopic observations. We calculate its X-ray ionization and the ensuing X-ray absorption line spectra in comparison with an XXM-Newton/EPIC spectrum of the narrow-line Seyfert AGN, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log(xi[erg cm/s]) = 5-6 and a hydrogen-equivalent column density on the order of 1e23 cm-2, outflowing at a sub-relativistic velocity of v/c = 0.1-0.2. The best-fit model favors its radial location at R = 200 Rs (Rs is the Schwarzschild radius), with a disk inner truncation radius at Rt = 30Rs. The overall K-shell feature in data is suggested to be dominated by Fe XXV with very little contribution from Fe XXVI and weakly-ionized iron, which is in a good agreement with a series of earlier analysis of the UFOs in various AGNs including PG 1211+143.

  12. Converting the Audience: A Conversation with Agnes Wilcox

    ERIC Educational Resources Information Center

    Becker, Becky

    2006-01-01

    This article presents a conversation with Agnes Wilcox, Executive Director of Prison Performing Arts in St. Louis, Missouri, about Prison Performing Arts. Although the average person might balk at the notion of interacting with prison inmates, finding it intimidating, worrisome, or self-sacrificial, for Wilcox, Prison Performing Arts is a…

  13. X-Ray Selected AGN in A Merging Cluster

    NASA Astrophysics Data System (ADS)

    Taylor, Joanna M.; Norman, D.; Soechting, I.; Coldwell, G.

    2012-01-01

    We investigate the X-ray AGN population and evolution in the merging galaxy cluster DLSCL J0522.2-4820 discovered via weak gravitational lensing shear from the Deep Lens Survey (DLS). Since weak lensing shear is dependent only on mass, it does not introduce the biases that typical cluster selection methods do. This cluster is of particular interest due to both its extended multiple X-ray emission peaks and the large number of X-ray point sources identified in the field. We measured the redshifts of X-ray AGN as well as cluster galaxies in order to investigate the 3-dimensional distribution and possible clustering of AGN in galaxy clusters. Of the 125 objects in our sample, 54 are galaxies in the cluster; the cluster redshift is determined to be z=0.2997±0.0096. This agrees well with a previous value of z=0.296±0.001. We identified several broad line AGN at high redshift including a quasar pair at redshift z=1.8. Currently, we have found no X-ray point sources to be within the cluster. This project was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program and the Department of Defense ASSURE program through Scientific Program Order No. 13 (AST-0754223) of the Cooperative Agreement No. AST-0132798 between the Association of Universities for Research in Astronomy (AURA) and the NSF.

  14. First Results from the NuSTAR AGN Physics Program

    NASA Astrophysics Data System (ADS)

    Brenneman, Laura; Fuerst, F.; Matt, G.; Walton, D.; Madejski, G. M.; Marinucci, A.; Elvis, M.; Risaliti, G.; Harrison, F.; Stern, D.; Boggs, S.; Christensen, F.; Craig, W. W.; Zhang, W.; NuSTAR Team

    2013-04-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR, launched June 2012) is revolutionizing our knowledge of the physics at work in active galactic nuclei (AGN). With its high collecting area, focusing optics and low background from 3-79 keV, NASA's newest X-ray observatory is providing an unprecedented look at the spectral and timing properties of AGN in this energy range, which have been notoriously difficult to access. NuSTAR has observed several AGN to date simultaneously with XMM-Newton, Suzaku and/or Swift for the purposes of understanding their coronal properties (e.g., plasma temperature, optical depth) and measuring the spins of their supermassive black holes. We present the first results from these observing campaigns, highlighting the spectral and timing analysis of the bright, nearby AGN IC 4329A, NGC 4151, NGC 1365 and MCG--6-30-15. These are the highest signal-to-noise datasets ever obtained across the 0.2-79 keV energy band for these three sources, allowing us to cleanly deconvolve the X-ray continuum, absorption and reflection components in each galaxy for the first time via time-averaged and time-resolved spectroscopy.

  15. Feedback from AGN: The Kinetic/Radio Luminosity Function

    NASA Astrophysics Data System (ADS)

    Melini, Gabriele; La Franca, Fabio; Fiore, Fabrizio

    2010-05-01

    We have measured the probability distribution function of the ratio RX = log L1.4/LX, where L1.4/LX = ν Lν(1.4 GHz)/LX(2-10 keV), between the 1.4 GHz and the unabsorbed 2-10 keV luminosities and its dependence on LX and z. We have used a complete sample of ~1800 hard X-ray selected AGN, observed in the 1.4 GHz band, cross-correlated in order to exclude FR II-type objects, and thus obtain a contemporaneous measure of the radio and X-ray emission. The distribution P(RX|LX,z) is shown in Figure 1. Convolution of the distribution P(RX|LX,z) with the 2-10 keV X-ray AGN luminosity function from La Franca et al. (2005) and the relations between radio power and kinetic energy from Best et al. (2006) and Willott et al. (1999) allows us to derive the AGN kinetic power and its evolution. As shown in Figure 1, our results are in good agreement with the predictions of the most recent models of galaxy formation and evolution (e.g., Croton et al. 2006), where AGN radio feedback is required to quench the star formation.

  16. Fast ionized X-ray absorbers in AGNs

    NASA Astrophysics Data System (ADS)

    Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

    2016-05-01

    We investigate the physics of the X-ray ionized absorbers often identified as warm absorbers (WAs) and ultra-fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically-driven accretion-disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad-Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk-wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating-cooling equilibrium state to compute the absorber's properties such as column density N_H, line-of-sight (LoS) velocity v, ionization parameter ξ, among others. Assuming that the wind density scales as n ∝ r-1, we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe Kα absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD-driven disk-wind scenario is not only consistent with the observed X-ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine.

  17. Unveiling the physics of AGN through X-ray variability

    NASA Astrophysics Data System (ADS)

    Hernández-García, L.; González-Martín, O.; Masegosa, J.; Márquez, I.

    2017-03-01

    Although variability is a general property characterizing active galactic nuclei (AGN), it is not well established whether the changes occur in the same way in every nuclei. The main purpose of this work is to study the X-ray variability pattern(s) in AGN selected at optical wavelengths in a large sample, including low ionization nuclear emission line regions (LINERs) and type 1.8, 1.9, and 2 Seyferts, using the public archives in Chandra and/or XMM–Newton. Spectra of the same source gathered at different epochs were simultaneously fitted to study long term variations; the variability patterns were studied allowing different parameters to vary during the spectral fit. Whenever possible, short term variations from the analysis of the light curves and long term UV flux variability were studied. Variations at X-rays in timescales of months/years are very common in all AGN families but short term variations are only found in type 1.8 and 1.9 Seyferts. The main driver of the long term X-ray variations seems to be related to changes in the nuclear power. Other variability patterns cannot be discarded in a few cases. We discuss the geometry and physics of AGN through the X-ray variability analysis.

  18. Increased Symmetric Dimethylarginine Level Is Associated with Worse Hospital Outcomes through Altered Left Ventricular Ejection Fraction in Patients with Acute Myocardial Infarction

    PubMed Central

    Lorin, Julie; Guilland, Jean-Claude; Stamboul, Karim; Guenancia, Charles; Cottin, Yves; Rochette, Luc; Vergely, Catherine; Zeller, Marianne

    2017-01-01

    Objectives We aimed to investigate whether SDMA- symmetric dimethylarginine -the symmetrical stereoisomer of ADMA- might be a marker of left ventricular function in AMI. Background Asymmetric dimethylarginine (ADMA) has been implicated in the prognosis after acute myocardial infarction (AMI) and heart failure (HF). Methods Cross sectional prospective study from 487 consecutive patients hospitalized <24 hours after AMI. Patients with HF on admission were excluded. Serum levels of ADMA, SDMA and L-arginine were determined using HPLC. Glomerular filtration rate (eGFR) was estimated based on creatinine levels. Outcomes were in-hospital severe HF, as defined by Killip class >2, and death. Results Patients were analysed based on SDMA tertiles. Sex, diabetes, dyslipidemia, and prior MI were similar for all tertiles. In contrast, age and hypertension increased across the tertiles (p<0.001). From the first to the last tertile, GRACE risk score was elevated while LVEF and eGFR was reduced. The rate of severe HF and death were gradually increased across the SDMA tertiles (from 0.6% to 7.4%, p = 0.006 and from 0.6% to 5.0%, p = 0.034, respectively). Backward logistic multivariate analysis showed that SDMA was an independent estimate of developing severe HF, even when adjusted for confounding (OR(95%CI): 8.2(3.0–22.5), p<0.001). Further, SDMA was associated with mortality, even after adjustment for GRACE risk score (OR(95%CI): 4.56(1.34–15.52), p = 0.015). Conclusions Our study showed for the first time that SDMA is associated with hospital outcomes, through altered LVEF and may have biological activity beyond renal function. PMID:28125604

  19. A radio view of high-energy emitting AGNs

    NASA Astrophysics Data System (ADS)

    Schulz, Robert Frank

    2016-07-01

    Active galactic nuclei (AGNs) are among the most energetic objects in the Universe. These galaxies that are dominated in part or even throughout the electromagnetic spectrum by emission from their central, compact region. AGNs are extensively studied by multi-wavelength observations. In the standard picture, the main driver of an AGN is a supermassive black hole (SMBH) in its centre that is surrounded by an accretion disk. Perpendicular to the disk, in the vicinity of highly magnetized SMBH relativistic outflows of plasma, so-called jets, can form on either side that can reach far beyond the host galaxy. Only about 10% of all AGNs are dominated by emission from these jets due to relativistic beaming effects and these so-called blazars dominate the extragalactic gamma-ray sky. It is commonly accepted that the low-energy emission (radio to UV/X-ray) is due to synchrotron emission from the jet. The high-energy emission is considered to stem from inverse-Compton scattering of photons on the jet particles, but different sources for these photons are discussed (internal or external to the AGN) and other models for the high-energy emission have also been proposed. The nature of the high-energy emission is strongly linked to the location of the emission region in the jet which requires a detailed understanding of the formation and evolution of jets. Radio observations especially using very long baseline interferometry (VLBI) provide the best way to gain direct information on the intrinsic properties of jets down to sub-pc scales, close to their formation region. In this thesis, I focus on the properties of three different AGNs, IC 310, PKS2004-447, and 3C 111 that belong to the small non-blazar population of gamma-ray-loud AGNs. I study them in detail with a variety of radio astronomical instruments with respect to their high-energy emission and in the context of the large monitoring programmes MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) and

  20. Understanding AGNs in the Local Universe through Optical Reverberation Mapping

    NASA Astrophysics Data System (ADS)

    Pei, Liuyi

    2016-01-01

    I present the results of observational projects aimed at measuring the mass of the black hole at the center of active galactic nuclei (AGNs) and understanding the structure and kinematics of the broad-line emitting gas within the black hole's sphere of influence.The first project aims to measure the black hole mass in the Kepler-field AGN KA1858. We obtained simultaneous spectroscopic data from the Lick Observatory 3-m telescope using the Kast Double Spectrograph and photometry data from five ground-based telescopes, and used reverberation mapping (RM) techniques to measure the emission-line light curves' lags relative to continuum variations. We obtained lags for H-beta, H-gamma, H-delta, and He II, and obtained the first black hole mass measurement for this object. Our results will serve as a reference point for future studies on relations between black hole mass and continuum variability characteristics using Kepler AGN light curves.The second project, in collaboration with the AGN STORM team, aims to understand the structure and dynamics of the broad line region (BLR) in NGC 5548 in both UV and optical wavelengths. To supplement 6 months of HST UV observations, we obtained simultaneous optical spectroscopic data from six ground-based observatories. We obtained emission-line lags for the optical H-beta and He II lines as well as velocity-resolved lag measurements for H-beta. We also compared the velocity-resolved lags for H-beta to the UV emission lines C IV and Ly-alpha and found similar lag profiles for all three lines.Finally, I will discuss my contributions to two other collaborations in AGN RM. A key component in RM is monitoring continuum variability, which is often done through ground-based photometry. I will present a pipeline that performs aperture photometry on any number of images of an AGN with WCS coordinates and immediately produces relative light curves. This pipeline enables quick looks of AGN variability in real time and has been used in the

  1. Evidence of increased mass fraction of NO 2 within real-world NO x emissions of modern light vehicles — derived from a reliable online measuring method

    NASA Astrophysics Data System (ADS)

    Alvarez, Robert; Weilenmann, Martin; Favez, Jean-Yves

    Ambient roadside concentrations of nitrogen dioxide (NO 2) have stabilized in recent years while concentrations of nitrogen oxides (NO x) decline. Oxidation catalytic converters of modern vehicles facilitating the formation of NO 2 in the exhaust line, especially in diesel cars equipped with original equipment manufacturer (OEM) particle filters, are assumed to be responsible. NO 2 is toxic and increased proportions of NO 2 in total NO x in the atmosphere cause higher ambient ozone concentrations. These observations lead to a need for reliable emission factors for NO and NO 2 for road vehicles, while only NO x is recorded in standard emission measurements. In this regard, it was recently shown that NO 2 needs to be detected by an adequate online measuring method. The present work provides novel insight into these topics gained from an experimental campaign carried out with modern gasoline and diesel vehicles of certification categories Euro 3 and Euro 4. Reliable emission factors for NO and NO 2 are presented for different driving situations, such as real-world driving, cold start and statutory tests, together with corresponding particle emission data. Highest emissions of NO x are recorded for diesel cars equipped with OEM particle filters with mass ratios of NO 2 within NO x of up to 70%. The NO x emissions exceed the statutory emission limit and real-world emissions are even more pronounced, especially in urban driving conditions. Their particle emissions are greatly reduced, but the contribution of NO 2 to soot oxidation is thought to be minor.

  2. Modeling the reverberation of optical polarization in AGN

    NASA Astrophysics Data System (ADS)

    Rojas Lobos, P. A.; Goosmann, R.; Marin, F.

    2016-12-01

    According to the standard paradigm, the strong and compact luminosity of active galactic nuclei (AGN) is due to multi-temperature black body emission originating from an accretion disk formed around a supermassive black hole. This central engine is thought to be surrounded by a dusty region along the equatorial plane and by ionized winds along the poles. The innermost regions cannot yet be resolved neither in the optical nor in the infrared and it is fair to say that we still lack a satisfactory understanding of the physical processes, geometry and composition of the central (sub-parsec) components of AGN. Like spectral or polarimetric observations, the reverberation data needs to be modeled in order to infer constraints on the AGN geometry (such as the inner radius or the half-opening angle of the dusty torus). In this research note, we present preliminary modeling results using a time-dependent Monte Carlo method to solve the radiative transfer in a simplified AGN set up. We investigate different model configurations using both polarization and time lags and find a high dependency on the geometry to the time-lag response. For all models there is a clear distinction between edge-on or face-on viewing angles for fluxes and time lags, the later showing a higher wavelength-dependence than the former. Time lags, polarization and fluxes point toward a clear dichotomy between the different inclinations of AGN, a method that could help us to determine the true orientation of the nucleus in Seyfert galaxies.

  3. Disentangling the AGN and Star-forming Contribution to the Sub-mJy Radio Counts

    NASA Astrophysics Data System (ADS)

    Seymour, Nick; Moss, D.; Dwelly, T.; McHardy, I.; Page, M.; Loaring, N.

    2007-05-01

    The up-turn of the faint, sub-mJy radio counts at 1.4GHz has now been known for ˜20years. Despite some theoretical and observational evidence that this is mainly due to a rapid increase in the radio emission from fast evolving star-formation in normal galaxies, direct determination of the relative contribution of Active Galactic Nuclei (AGN) and star-formation in individual galaxies remains elusive. The difficulty in identifying the physical processes in each galaxy can be attributed to their faint optical nature, i.e. 20% of sub-mJy radio sources have R>25. We present a unique data set from the `XMM/ ROSAT 13hr deep field' consisting of deep Very Large Array data (7.5uJy rms at 1.4GHz) and Giant Metre Radio-wave Telescope data (20uJy rms at 610MHz) providing radio spectral indices of ˜500 sub-mJy radio sources. We also have very deep GTO IRAC (3.6-8um) and MIPS (24-160um) Spitzer observations, supplementing our deep optical/near-IR multi-band observations. Using a combination of radio spectra/morphology, IRAC colours, and our deep XMM/Chandra data we are able to largely de-convolve the AGN and star-forming contribution to each radio source. We find that the bulk of the sub-mJy radio population are powered by star-formation, but that AGN are detected at all flux densities albeit at a decreasing rate at fainter flux densities. These AGN include radio sources that otherwise appear to be normal, z<1, star-forming galaxies and several at high redshift, z>2 - low luminosity counterparts to classical high redshift radio galaxies. The contribution of the star-forming galaxies to the faint counts is consistent with the rapid evolution of the local star-forming radio luminosity function and the rapid increase in the star-formation rate density up to z=1-2.

  4. Modification of A Tumor Antigen Determinant to Improve Peptide/MHC Stability Is Associated with Increased Immunogenicity and Cross-Priming A Larger Fraction of CD8+ T Cells1

    PubMed Central

    Watson, Alan M.; Mylin, Lawrence M.; Thompson, Megan M.; Schell, Todd D.

    2012-01-01

    Altered peptide ligands (APLs) with enhanced binding to MHC class I (MHC-I) can increase the CD8+ T cell response to native antigens, including tumor antigens. Here we investigate the influence of peptide-MHC (pMHC) stability on recruitment of tumor antigen-specific CD8+ T cells through cross-priming. Among the four known H-2b-restricted CD8+ T cell determinants within SV40 large tumor antigen (TAg), the site V determinant (489QGINNLDNL497) forms relatively low-stability pMHC and is characteristically immunorecessive. Absence of detectable site V-specific CD8+ T cells following immunization with wild type TAg is due in part to inefficient cross-priming. We mutated non-anchor residues within the TAg site V determinant that increased pMHC-stability but preserved recognition by both T cell receptor transgenic and polyclonal endogenous T cells. Using a novel approach to quantify the fraction of naïve T cells triggered through cross-priming in vivo, we show that immunization with TAg variants expressing higher-stability determinants increased the fraction of site V-specific T cells cross-primed and effectively overcame the immunorecessive phenotype. In addition, using MHC-I tetramer-based enrichment we demonstrate for the first time that endogenous site V-specific T cells are primed following wild type TAg immunization despite their low initial frequency, but that the magnitude of T cell accumulation is enhanced following immunization with a site V variant TAg. Our results demonstrate that site V APLs cross-prime a higher fraction of available T cells, providing a potential mechanism for high-stability APLs to enhance immunogenicity and accumulation of T cells specific for the native determinant. PMID:23175697

  5. Gamma-ray monitoring of AGN and galactic black hole candidates by the Gamma-Ray Observatory

    NASA Technical Reports Server (NTRS)

    Wheaton, Wm. A.; Ling, James C.; Skelton, R. T.; Harmon, Alan; Fishman, Gerald J.; Meegan, Charles A.; Paciesas, William S.; Rubin, Brad; Wilson, Robert B.; Gruber, Duane E.

    1992-01-01

    The Burst and Transient Spectroscopy Experiment (BATSE) on the Compton Gamma-Ray Observatory has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both AGN and Galactic black hole candidates such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Progress in background modeling indicates that the data accept region, or fit window tau, around the occultation step can be substantially increased over that conservatively assumed in earlier estimates of BATSE's Earth occultation sensitivity. We show samples of large-tau fits to background and source edges. As a result we expect to be able to perform long-term monitoring of Cygnus X-1 and many of the brighter AGN for the duration of the CGRO mission.

  6. A NEW INFRARED COLOR CRITERION FOR THE SELECTION OF 0 < z < 7 AGNs: APPLICATION TO DEEP FIELDS AND IMPLICATIONS FOR JWST SURVEYS

    SciTech Connect

    Messias, H.; Afonso, J.; Salvato, M.; Mobasher, B.; Hopkins, A. M.

    2012-08-01

    It is widely accepted that observations at mid-infrared (mid-IR) wavelengths enable the selection of galaxies with nuclear activity, which may not be revealed even in the deepest X-ray surveys. Many mid-IR color-color criteria have been explored to accomplish this goal and tested thoroughly in the literature. Besides missing many low-luminosity active galactic nuclei (AGNs), one of the main conclusions is that, with increasing redshift, the contamination by non-active galaxies becomes significant (especially at z {approx}> 2.5). This is problematic for the study of the AGN phenomenon in the early universe, the main goal of many of the current and future deep extragalactic surveys. In this work new near- and mid-IR color diagnostics are explored, aiming for improved efficiency-better completeness and less contamination-in selecting AGNs out to very high redshifts. We restrict our study to the James Webb Space Telescope wavelength range (0.6-27 {mu}m). The criteria are created based on the predictions by state-of-the-art galaxy and AGN templates covering a wide variety of galaxy properties, and tested against control samples with deep multi-wavelength coverage (ranging from the X-rays to radio frequencies). We show that the colors K{sub s} - [4.5], [4.5] - [8.0], and [8.0] - [24] are ideal as AGN/non-AGN diagnostics at, respectively, z {approx}< 1, 1 {approx}< z {approx}< 2.5, and z {approx}> 2.5-3. However, when the source redshift is unknown, these colors should be combined. We thus develop an improved IR criterion (using K{sub s} and IRAC bands, KI) as a new alternative at z {approx}< 2.5. KI does not show improved completeness (50%-60% overall) in comparison to commonly used Infrared Array Camera (IRAC) based AGN criteria, but is less affected by non-AGN contamination (revealing a >50%-90% level of successful AGN selection). We also propose KIM (using K{sub s} , IRAC, and MIPS 24 {mu}m bands, KIM), which aims to select AGN hosts from local distances to as far

  7. AGN feedback in the nucleus of M 51

    NASA Astrophysics Data System (ADS)

    Querejeta, M.; Schinnerer, E.; García-Burillo, S.; Bigiel, F.; Blanc, G. A.; Colombo, D.; Hughes, A.; Kreckel, K.; Leroy, A. K.; Meidt, S. E.; Meier, D. S.; Pety, J.; Sliwa, K.

    2016-10-01

    AGN feedback is invoked as one of the most relevant mechanisms that shape the evolution of galaxies. Our goal is to understand the interplay between AGN feedback and the interstellar medium in M 51, a nearby spiral galaxy with a modest AGN and a kpc-scale radio jet expanding through the disc of the galaxy. For this purpose, we combine molecular gas observations in the CO(1-0) and HCN(1-0) lines from the Plateau de Bure interferometer with archival radio, X-ray, and optical data. We show that there is a significant scarcity of CO emission in the ionisation cone, while molecular gas emission tends to accumulate towards the edges of the cone. The distribution and kinematics of CO and HCN line emission reveal AGN feedback effects out to r ~ 500 pc, covering the whole extent of the radio jet, with complex kinematics in the molecular gas which displays strong local variations. We propose that this is the result of the almost coplanar jet pushing on molecular gas in different directions as it expands; the effects are more pronounced in HCN than in CO emission, probably as the result of radiative shocks. Following previous interpretation of the redshifted molecular line in the central 5'' as caused by a molecular outflow, we estimate the outflow rates to be ṀH2 ~ 0.9 M⊙/ yr and Ṁdense ~ 0.6 M⊙/ yr, which are comparable to the molecular inflow rates (~1 M⊙/ yr); gas inflow and AGN feedback could be mutually regulated processes. The agreement with findings in other nearby radio galaxies suggests that this is not an isolated case, and is probably the paradigm of AGN feedback through radio jets, at least for galaxies hosting low-luminosity active nuclei. The reduced HCN(1-0) datacube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A118

  8. Do some AGN lack X-ray emission?

    NASA Astrophysics Data System (ADS)

    Simmonds, C.; Bauer, F. E.; Thuan, T. X.; Izotov, Y. I.; Stern, D.; Harrison, F. A.

    2016-12-01

    Context. Intermediate-mass black holes (IMBHs) are thought to be the seeds of early supermassive black holes (SMBHs). While ≳100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of considerable interest and importance. Additionally, finding significant numbers of IMBHs in metal-poor systems would be particularly intriguing, since such systems may represent local analogs of primordial galaxies, and therefore could provide clues of early accretion processes. Aims: Here we study in detail several candidate active galactic nuclei (AGN) found in metal-poor hosts. Methods: We utilize new X-ray and optical observations to characterize these metal-poor AGN candidates and compare them against known AGN luminosity relations and well-characterized IMBH/SMBH samples. Results: Despite having clear broad optical emission lines that are long-lived (≳10-13 yr), these candidate AGN appear to lack associated strong X-ray and hard UV emission, lying at least 1-2 dex off the known AGN correlations. If they are IMBHs/SMBHs, our constraints imply that they either are not actively accreting, their accretion disks are fully obscured along our line-of-sight, or their accretion disks are not producing characteristic high energy emission. Alternatively, if they are not AGN, then their luminous broad emission lines imply production by extreme stellar processes. The latter would have profound implications on the applicability of broad lines for mass estimates of massive black holes. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A64

  9. Fraction collector for electrophoresis

    NASA Technical Reports Server (NTRS)

    Bier, M.

    1977-01-01

    Rotating-tube electrophoresis apparatus employs rotating jet of eluting buffer to reduce effects of convection during separation. Designed for separation of microorganisms and biological species, system combines gravity/gradient compensating of lumen with buffer flush at fraction outlet to increase separation efficiency.

  10. Suzaku Discovery of Ultra-fast Outflows in Radio-loud AGN

    NASA Astrophysics Data System (ADS)

    Sambruna, Rita M.; Tombesi, F.; Reeves, J.; Braito, V.; Gofford, J.; Cappi, M.

    2010-03-01

    We present the results of an analysis of the 3.5--10.5 keV spectra of five bright Broad-Line Radio Galaxies (BLRGs) using proprietary and archival Suzaku observations. In three sources -- 3C 111, 3C 120, and 3C 390.3 -- we find evidence, for the first time in a radio-loud AGN, for absorption features at observed energies 7 keV and 8--9 keV, with high significance according to both the F-test and extensive Monte Carlo simulations (99% or larger). In the remaining two BLRGs, 3C 382 and 3C 445, there is no evidence for such absorption features in the XIS spectra. If interpreted as due to Fe XXV and/or Fe XXVI K-shell resonance lines, the absorption features in 3C 111, 3C 120, and 3C 390.3 imply an origin from an ionized gas outflowing with velocities in the range v 0.04-0.15c, reminiscent of Ultra-Fast Outflows (UFOs) previously observed in radio-quiet Seyfert galaxies. A fit with specific photoionization models gives ionization parameters log ξ 4--5.6 erg s-1 cm and column densities of NH 1022-23 cm-2, similar to the values observed in Seyferts. Based on light travel time arguments, we estimate that the UFOs in the three BLRGs are located within 20--500 gravitational radii from the central black hole, and thus most likely are connected to disk winds/outflows. Our estimates show that the UFOs mass outflow rate is comparable to the accretion rate and their kinetic energy a significant fraction of the AGN bolometric luminosity, making these outflows significant for the global energetic of these systems, in particular for mechanisms of jet formation.

  11. Biochemical Characterization of Paracoccidioides brasiliensis α-1,3-Glucanase Agn1p, and Its Functionality by Heterologous Expression in Schizosaccharomyces pombe

    PubMed Central

    Villalobos-Duno, Héctor; San-Blas, Gioconda; Paulinkevicius, Maryan; Sánchez-Martín, Yolanda; Nino-Vega, Gustavo

    2013-01-01

    α-1,3-Glucan is present as the outermost layer of the cell wall in the pathogenic yeastlike (Y) form of Paracoccidioides brasiliensis. Based on experimental evidence, this polysaccharide has been proposed as a fungal virulence factor. To degrade α-1,3-glucan and allow remodeling of the cell wall, α-1,3-glucanase is required. Therefore, the study of this enzyme, its encoding gene, and regulatory mechanisms, might be of interest to understand the morphogenesis and virulence process in this fungus. A single gene, orthologous to other fungal α-1,3-glucanase genes, was identified in the Paracoccidioides genome, and labeled AGN1. Transcriptional levels of AGN1 and AGS1 (α-1,3-glucan synthase-encoding gene) increased sharply when the pathogenic Y phase was cultured in the presence of 5% horse serum, a reported booster for cell wall α-1,3-glucan synthesis in this fungus. To study the biochemical properties of P. brasiliensis Agn1p, the enzyme was heterologously overexpressed, purified, and its activity profile determined by means of the degradation of carboxymethyl α-1,3-glucan (SCMG, chemically modified from P. brasiliensis α-1,3-glucan), used as a soluble substrate for the enzymatic reaction. Inhibition assays, thin layer chromatography and enzymatic reactions with alternative substrates (dextran, starch, chitin, laminarin and cellulose), showed that Agn1p displays an endolytic cut pattern and high specificity for SCMG. Complementation of a Schizosaccharomyces pombe agn1Δ strain with the P. brasiliensis AGN1 gene restored the wild type phenotype, indicating functionality of the gene, suggesting a possible role of Agn1p in the remodeling of P. brasiliensis Y phase cell wall. Based on amino acid sequence, P. brasiliensis Agn1p, groups within the family 71 of fungal glycoside hydrolases (GH-71), showing similar biochemical characteristics to other members of this family. Also based on amino acid sequence alignments, we propose a subdivision of fungal GH-71 into at

  12. THE ORIGIN OF DOUBLE-PEAKED NARROW LINES IN ACTIVE GALACTIC NUCLEI. I. VERY LARGE ARRAY DETECTIONS OF DUAL AGNs AND AGN OUTFLOWS

    SciTech Connect

    Müller-Sánchez, F.; Comerford, J. M.; Nevin, R.; Barrows, R. S.; Cooper, M. C.; Greene, J. E.

    2015-11-10

    We have examined a subset of 18 active galactic nuclei (AGNs) drawn from a sample of 81 galaxies that possess double-peaked narrow optical emission line spectra in the Sloan Digital Sky Survey, have 2 optical AGN emission components separated by >0.″2, and are detected in the Faint Images of the Radio Sky at Twenty-centimeters survey. Without follow-up observations, the sources of the double-peaked narrow emission lines are uncertain, and may be produced by kiloparsec-scale separation dual active supermassive black holes, AGN outflows, or disk rotation. In this work, we propose a new methodology to characterize double-peaked narrow emission line galaxies based on optical long-slit spectroscopy and high-resolution multi-band Very Large Array observations. The nature of the radio emission in the sample galaxies is varied. Of the 18 galaxies, we detect 2 compact flat-spectrum radio cores with projected spatial separations on the sky between 0.6 and 1.6 kpc in 3 galaxies: J1023+3243, J1158+3231, and J1623+0808. The two radio sources are spatially coincident with the two optical components of ionized gas with AGN-like line ratios, which confirms the presence of dual AGNs in these three galaxies. Dual AGNs account for only ∼15% (3/18) of the double-peaked AGNs in our sample. Gas kinematics produce ∼75% (13/18) of the double-peaked narrow emission lines, distributed in the following way: seven AGN wind-driven outflows, five radio-jet driven outflows, and one rotating narrow-line region. The remaining 10% (2/18) are ambiguous cases. Our method demonstrates the power of spatially resolved spectroscopy and high-resolution radio observations for the identification of AGN outflows and AGN pairs with angular separations as small as 0.″18.

  13. The first experiment of accretion disc tomography in AGNs

    NASA Astrophysics Data System (ADS)

    Risaliti, Guido

    2011-10-01

    We propose four one-orbit observations of the AGN in NGC~1365, with the main aim of measuring the spectral variations during an eclipse. This source showed extraordinary variability in the past observations, indicating a high probability of catching an eclipse by a Compton-thick cloud in the proposed observation time. The differences in the shape of the iron broad emission line at different phases of the eclipse would be a decisive proof of the relativistic effects on this line due to the strong gravity and fast orbital motion of the inner part of the accretion disc. In addition to this unique experiment, the spectral complexity of NGC~1365 (with the highest S/N detection of iron absorption lines in AGNs) makes it the ideal target for a deep ``legacy'' observation.

  14. NGC 741: Mergers and AGN feedback at the group scale

    NASA Astrophysics Data System (ADS)

    Vrtilek, Jan

    2014-09-01

    While AGN and mergers are thought to play important roles in group and cluster evolution, their effects in galaxy groups are poorly understood. We propose to observe the NGC 741 group, which hosts both an old central radio galaxy, and a spectacular infalling head-tail source. Strongly-bent jets, a 100kpc radio trail and intriguing narrow X-ray filaments suggest that NGC 742 is moving trans-sonically, undergoing stripping and shock heating. NGC 741 possesses both an old, faint radio lobe and an X-ray cavity, whose inflating plasma may have unusual properties. We request Chandra and XMM observations of the group with the goal of examining the roles of the central AGN and infalling galaxy in heating the intra-group medium, and determining the origin of the intriguing X-ray filaments.

  15. A Unified View of X-ray Absorbers in AGNs and XRBs with MHD Winds

    NASA Astrophysics Data System (ADS)

    Fukumura, Keigo; Kazanas, Demosthenes; Shrader, Chris R.; Tombesi, Francesco; Behar, Ehud; Contopoulos, John

    2016-01-01

    The presence of UV and X-ray absorbers (aka. warm absorbers or WAs) has been long known for decades from extensive spectroscopic studies across diverse AGN populations such as nearby Seyfert galaxies and distant quasars. Furthermore, another class of seemingly distinct type of absorbers, ultra-fast outflows or UFOs, is becoming increasingly known today. Nonetheless, a physical identification of such absorbers, such as geometrical property and physical conditions, is very elusive to date despite the recent state-of-the-art observations. We develop a coherent scenario in which the detected absorbers are driven primarily (if not exclusively) by the action of global magnetic fields originating from a black hole accretion disk. In the context of MHD disk-wind of density profile of n~1/r, it is found that the properties of the observed WAs/UFOs are successfully described assuming a characteristic SED. As a case study, we analyze PG1211+143 and GRO J1655-40 to demonstrate that our wind model can systematically unify apparently diverse absorbers in both AGNs and XRBs in terms of explaining their global behavior as well as individual spectral lines.

  16. Announcment: Conference on Obscured AGN Across Cosmic Time

    NASA Astrophysics Data System (ADS)

    2006-12-01

    Current deep surveys, notably in X-rays and the mid-IR, are making it possible to carry out a census of essentially all the luminous AGN in the Universe. By pene-trating the obscuration that, in Type 2 sources, hides the nuclear regions in the UV to the near-IR spectrum, these new surveys are finding the radio quiet coun-terparts of the powerful radio galaxies.

  17. The international AGN watch: A multiwavelength monitoring consortium

    NASA Technical Reports Server (NTRS)

    Alloin, D.; Clavel, J.; Peterson, B. M.; Reichert, G. A.; Stirpe, G. M.

    1994-01-01

    The International AGN Watch, an informal consortium of over 100 astronomers, was established to coordinate multiwavelength monitoring of a limited number of active galactic nuclei and thus obtain comprehensive continuum and emission-line variability data with unprecedented temporal and wavelength coverage. We summarize the principal scientific results from two completed space-based and ground-based campaigns on the Seyfert galaxies NGC 5548 and NGC 3783. We describe a project in progress and outline our future plans.

  18. The synthesis and characterization of Ag-N dual-doped p-type ZnO: experiment and theory.

    PubMed

    Duan, Li; Wang, Pei; Yu, Xiaochen; Han, Xiao; Chen, Yongnan; Zhao, Peng; Li, Donglin; Yao, Ran

    2014-03-07

    Ag-N dual-doped ZnO films have been fabricated by a chemical bath deposition method. The p-type conductivity of the dual-doped ZnO:(Ag, N) is stable over a long period of time, and the hole concentration in the ZnO:(Ag, N) is much higher than that in mono-doped ZnO:Ag or ZnO:N. We found that this is because AgZn-NO complex acceptors can be formed in ZnO:(Ag, N). First-principles calculations show that the complex acceptors generate a fully occupied band above the valance band maximum, so the acceptor levels become shallower and the hole concentration is increased. Furthermore, the binding energy of the Ag-N complex in ZnO is negative, so ZnO:(Ag, N) can be stable. These results indicate that the Ag-N dual-doping may be expected to be a potential route to achieving high-quality p-type ZnO for use in a variety of devices.

  19. Multidimensional Separation Using HILIC and SCX Pre-fractionation for RP LC-MS/MS Platform with Automated Exclusion List-based MS Data Acquisition with Increased Protein Quantification

    PubMed Central

    Zhou, Yu; Meng, Zhen; Edman-Woolcott, Maria; Hamm-Alvarez, Sarah F; Zandi, Ebrahim

    2015-01-01

    Liquid chromatography–mass spectrometry (LC-MS) based proteomics is one of the most widely used analytical platforms for global protein discovery and quantification. One of the challenges is the difficulty of identifying low abundance biomarker proteins from limited biological samples. Extensive fractionation could expand proteomics dynamic range, however, at the cost of high sample and time consumption. Extensive fractionation would increase the sample need and the labeling cost. Also quantitative proteomics depending on high resolution MS have the limitation of spectral acquisition speed. Those practical problems hinder the in-depth quantitative proteomics analysis such as tandem mass tag (TMT) experiments. We found the joint use of hydrophilic interaction liquid chromatography (HILIC) and strong cation exchange Chromatography (SCX) prefractionation at medium level could improve MS/MS efficiency, increase proteome coverage, shorten analysis time and save valuable samples. In addition, we scripted a program, Exclusion List Convertor (ELC), which automates and streamlines data acquisition workflow using the precursor ion exclusion (PIE) method. PIE reduces redundancy of high abundance MS/MS analyses by running replicates of the sample. The precursor ions detected in the initial run(s) are excluded for MS/MS in the subsequent run. We compared PIE methods with standard data dependent acquisition (DDA) methods running replicates without PIE for their effectiveness in quantifying TMT-tagged peptides and proteins in mouse tears. We quantified a total of 845 proteins and 1401 peptides using the PIE workflow, while the DDA method only resulted in 347 proteins and 731 peptides. This represents a 144% increase of protein identifications as a result of PIE analysis. PMID:26807013

  20. Triggering star formation by both radiative and mechanical AGN feedback

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Gan, Zhao-Ming; Xie, Fu-Guo

    2013-08-01

    We perform two dimensional hydrodynamic numerical simulations to study the positive active galactic nucleus (AGN) feedback which triggers, rather than suppresses, star formation. Recently, it was shown by Nayakshin et al. and Ishibashi et al. that star formation occurs when the cold interstellar medium (ISM) is squeezed by the impact of mass outflow or radiation pressure, respectively. Mass outflow is ubiquitous in this astrophysical context, and radiation pressure is also important if the AGN is luminous. For the first time in this subject, we incorporate both mass outflow feedback and radiative feedback into our model. Consequently, the ISM is shocked into shells by the AGN feedback, and these shells soon fragment into clumps and filaments because of Rayleigh-Taylor and thermal instabilities. We have two major findings: (1) the star formation rate can indeed be very large in the clumps and filaments. However, the resultant star formation rate density is too large compared with previous works, which is mainly because we ignore the fact that most of the stars that are formed would be disrupted when they move away from the galactic center. (2) Although radiation pressure feedback has a limited effect, when mass outflow feedback is also included, they reinforce each other. Specifically, in the gas-poor case, mass outflow is always the dominant contributor to feedback.

  1. Compton Reflection in AGN with Simbol-X

    NASA Astrophysics Data System (ADS)

    Beckmann, V.; Courvoisier, T. J.-L.; Gehrels, N.; Lubiński, P.; Malzac, J.; Petrucci, P. O.; Shrader, C. R.; Soldi, S.

    2009-05-01

    AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the simulations with recent observations on these sources by INTEGRAL, Swift and Suzaku. Constraining reflection models for AGN with Simbol-X will help us to get a clear view of the processes and geometry near to the central engine in AGN, and will give insight to which sources are responsible for the Cosmic X-ray background at energies >20 keV.

  2. VizieR Online Data Catalog: AGN from the RASS (Bade+, 1995)

    NASA Astrophysics Data System (ADS)

    Bade, N.; Fink, H. H.; Engels, D.; Voges, W.; Hagen, H.-J.; Wisotzki, L.; Reimers, D.

    1995-02-01

    This paper presents long slit CCD spectroscopy and X-ray data of 283 AGN detected in the ROSAT-All Sky Survey (RASS). Basis of the sample is the pre-identification of 4651 RASS sources on 134 sky fields (covering in total ~3500sq.deg.). The 283 presented AGN were selected from 1253 AGN candidates resulting from the pre-identification work. (3 data files).

  3. Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

    NASA Astrophysics Data System (ADS)

    Ballantyne, David R.

    2016-04-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of AGN evolution stretching back to z˜5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

  4. SPT0346-52: Negligible AGN Activity in a Compact, Hyper-starburst Galaxy at z = 5.7

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony. H.; Vieira, J. D.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Brandt, W. N.; de Breuck, C.; Carlstrom, J. E.; Chapman, S. C.; Gullberg, B.; Hezaveh, Y.; Litke, K.; Malkan, M.; Marrone, D. P.; McDonald, M.; Murphy, E. J.; Spilker, J. S.; Sreevani, J.; Stark, A. A.; Strandet, M.; Wang, S. X.

    2016-12-01

    We present Chandra ACIS-S and Australia Telescope Compact Array (ATCA) radio continuum observations of the strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter SPT0346-52) at z = 5.656. This galaxy has also been observed with ALMA, HST, Spitzer, Herschel, Atacama Pathfinder EXperiment, and the Very Large Telescope. Previous observations indicate that if the infrared (IR) emission is driven by star formation, then the inferred lensing-corrected star formation rate (SFR) (˜4500 M ⊙ yr-1) and SFR surface density ΣSFR (˜2000 M ⊙ yr-1 kpc-2) are both exceptionally high. It remained unclear from the previous data, however, whether a central active galactic nucleus (AGN) contributes appreciably to the IR luminosity. The Chandra upper limit shows that SPT0346-52 is consistent with being star formation dominated in the X-ray, and any AGN contribution to the IR emission is negligible. The ATCA radio continuum upper limits are also consistent with the FIR-to-radio correlation for star-forming galaxies with no indication of an additional AGN contribution. The observed prodigious intrinsic IR luminosity of (3.6 ± 0.3) × 1013 L ⊙ originates almost solely from vigorous star formation activity. With an intrinsic source size of 0.61 ± 0.03 kpc, SPT0346-52 is confirmed to have one of the highest ΣSFR of any known galaxy. This high ΣSFR, which approaches the Eddington limit for a radiation pressure supported starburst, may be explained by a combination of very high star formation efficiency and gas fraction.

  5. VizieR Online Data Catalog: Gamma-ray AGN type determination (Hassan+, 2013)

    NASA Astrophysics Data System (ADS)

    Hassan, T.; Mirabal, N.; Contreras, J. L.; Oya, I.

    2013-11-01

    In this paper, we employ Support Vector Machines (SVMs) and Random Forest (RF) that embody two of the most robust supervised learning algorithms available today. We are interested in building classifiers that can distinguish between two AGN classes: BL Lacs and FSRQs. In the 2FGL, there is a total set of 1074 identified/associated AGN objects with the following labels: 'bzb' (BL Lacs), 'bzq' (FSRQs), 'agn' (other non-blazar AGN) and 'agu' (active galaxies of uncertain type). From this global set, we group the identified/associated blazars ('bzb' and 'bzq' labels) as the training/testing set of our algorithms. (2 data files).

  6. The sharpest view of the local AGN population at mid-infrared wavelengths

    NASA Astrophysics Data System (ADS)

    Asmus, Daniel; Hönig, Sebastian F.; Gandhi, Poshak; Smette, Alain; Duschl, Wolfgang J.

    2014-07-01

    We present the largest mid-infrared (MIR) atlas of active galactic nuclei at sub-arcsec spatial scales containing 253 objects with a median redshift of 0.016. It comprises all available ground-based high-angular resolution MIR observations performed to date with 8-meter class telescopes and includes 895 photometric measurements. All types of AGN are present in the atlas, which also includes 80 per cent of the 9-month BAT AGN sample. Therefore, this atlas and its subsamples are very well-suited for AGN unification studies. A first application of the atlas is the extension of the MIR-X-ray luminosity correlation for AGN.

  7. Investigating the host galaxies of luminous AGN in the local universe with integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    McElroy, Rebecca; Croom, Scott; Husemann, Bernd; Close AGN Reference Survey; SAMI Galaxy Survey

    2017-01-01

    This thesis investigates how galaxies and their super massive black holes coevolve. We use integral field spectroscopy to search for evidence of AGN feedback and triggering. We demonstrate that outflows are ubiquitous among luminous local type 2 AGN using observations from the AAT's SPIRAL instrument. Using multiple component Gaussian emission line decomposition we are able to disentangle the kinematic and ionisation properties of these winds. This allows us to argue that the outflows from these AGN are directly impacting the surrounding ISM within the galaxies. We search for evidence of AGN triggering using data from The Close AGN Reference Survey (CARS). CARS aims to provide a detailed multi-wavelength view of 40 nearby (0.01 < z < 0.06) unobscured AGN to study the link between AGN and their host galaxies. The primary CARS observations come from the MUSE integral field unit on the VLT, and complementary multi-wavelength observations have been approved from SOFIA, Chandra, VLA, HST, and others. We compare the stellar kinematics of active galaxies from CARS to similar inactive galaxies. We then use kinemetry to estimate the degree of dynamical disturbance, to determine whether active nuclei are preferentially hosted in dynamically disturbed or merging systems. Finally, we highlight the discovery of an AGN that has changed spectral type not once, but twice. So called ‘changing look’ AGN are an uncommon phenomenon, but twice changed AGN are much rarer. This AGN first transitioned from a narrow line AGN (type 2) to a broad line AGN (type 1) in the 1980s. It was recently observed as part of CARS. Examination of the MUSE data for this particular source showed that it no longer had the spectral features typical of a type 1 AGN. The continuum emission from the accretion disk was no longer visible and the broad lines were dramatically diminished. In this talk we describe the possible reasons for this change, supported by analysis of multi-epoch optical photometry and

  8. Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses, and host-subtracted AGN luminosities

    NASA Astrophysics Data System (ADS)

    Haas, M.; Chini, R.; Ramolla, M.; Pozo Nuñez, F.; Westhues, C.; Watermann, R.; Hoffmeister, V.; Murphy, M.

    2011-11-01

    Photometric reverberation mapping employs a wide band pass to measure the AGN continuum variations and a suitable narrow band to trace the echo of an emission line in the broad line region (BLR). The narrow band catches both the emission line and the underlying continuum, and one needs to extract the pure emission line light curve. We performed a test on two local AGNs, PG0003+199 and Ark120, by observing well-sampled broad- (B, V) and narrow-band light curves with the robotic 15 cm telescope VYSOS-6 on Cerro Armazones, Chile. We find that, as long as the emission line contributes 50% to the band pass, the pure emission line light curve can be reconstructed from photometric monitoring data so that the time lag τ can be measured. For both objects the lags are consistent with spectroscopic reverberation results. We calculated virial black hole masses in agreement with literature values, by combining the BLR size RBLR (τ) from photometric monitoring with the velocity dispersion of a single contemporaneous spectrum. Applying the flux variation gradient method, we estimate the host galaxy contribution in the apertures used and the host-subtracted restframe 5100 Å luminosity LAGN. Our LAGN differs significantly from previous estimates, placing both sources ~50% closer to the RBLR - LAGN relation. This suggests that the scatter in the current RBLR - LAGN relation is largely caused by uncertainties in RBLR due to undersampled light curves and by uncertainties in the host-subtracted AGN luminosities inferred so far. If the scatter can be reduced, then two quasar samples matching in RBLR should also match in intrinsic LAGN, independent of redshift, thus offering the prospect of probing cosmological models. Photometric reverberation mapping opens the door to efficiently measuring hundreds of BLR sizes and host-subtracted AGN luminosities even with small telescopes, but also routinely with upcoming large survey telescopes like the LSST.

  9. let-7 Overexpression Leads to an Increased Fraction of Cells in G2/M, Direct Down-regulation of Cdc34, and Stabilization of Wee1 Kinase in Primary Fibroblasts*S⃞

    PubMed Central

    Legesse-Miller, Aster; Elemento, Olivier; Pfau, Sarah J.; Forman, Joshua J.; Tavazoie, Saeed; Coller, Hilary A.

    2009-01-01

    microRNAs play a critically important role in a wide array of biological processes including those implicated in cancer, neuro-degenerative and metabolic disorders, and viral infection. Although we have begun to understand microRNA biogenesis and function, experimental demonstration of their functional effects and the molecular mechanisms by which they function remains a challenge. Members of the let-7/miR-98 family play a critical role in cell cycle control with respect to differentiation and tumorigenesis. In this study, we show that exogenous addition of pre-let-7 in primary human fibroblasts results in a decrease in cell number and an increased fraction of cells in the G2/M cell cycle phase. Combining microarray techniques with DNA sequence analysis to identify potential let-7 targets, we discovered 838 genes with a let-7 binding site in their 3′-untranslated region that were down-regulated upon overexpression of let-7b. Among these genes is cdc34, the ubiquitin-conjugating enzyme of the Skp1/cullin/F-box (SCF) complex. Cdc34 protein levels are strongly down-regulated by let-7 overexpression. Reporter assays demonstrated direct regulation of the cdc34 3′-untranslated region by let-7. We hypothesized that low Cdc34 levels would result in decreased SCF activity, stabilization of the SCF target Wee1, and G2/M accumulation. Consistent with this hypothesis, small interfering RNA-mediated down-regulation of Wee1 reversed the G2/M phenotype induced by let-7 overexpression. We conclude that Cdc34 is a functional target of let-7 and that let-7 induces down-regulation of Cdc34, stabilization of the Wee1 kinase, and an increased fraction of cells in G2/M in primary fibroblasts. PMID:19126550

  10. Fatty acid composition in major depression: decreased omega 3 fractions in cholesteryl esters and increased C20: 4 omega 6/C20:5 omega 3 ratio in cholesteryl esters and phospholipids.

    PubMed

    Maes, M; Smith, R; Christophe, A; Cosyns, P; Desnyder, R; Meltzer, H

    1996-04-26

    Recently, there were some reports that major depression may be accompanied by alterations in serum total cholesterol, cholesterol ester and omega 3 essential fatty acid levels and by an increased C20: 4 omega 6/C20: 5 omega 3, i.e., arachidonic acid/eicosapentaenoic, ratio. The present study aimed to examine fatty acid composition of serum cholesteryl esters and phospholipids in 36 major depressed, 14 minor depressed and 24 normal subjects. Individual saturated (e.g., C14:0; C16:0, C18:0) and unsaturated (e.g., C18:1, C18:2, C20:4) fatty acids in phospholipid and cholesteryl ester fractions were assayed and the sums of the percentages of omega 6 and omega 3, saturated, branched chain and odd chain fatty acids, monoenes as well as the ratios omega 6/omega 3 and C20:4 omega 6/C20:5 omega 3 were calculated. Major depressed subjects had significantly higher C20:4 omega 6/C20:5 omega 3 ratio in both serum cholesteryl esters and phospholipids and a significantly increased omega 6/omega 3 ratio in cholesteryl ester fraction than healthy volunteers and minor depressed subjects. Major depressed subjects had significantly lower C18:3 omega 3 in cholesteryl esters than normal controls. Major depressed subjects showed significantly lower total omega 3 polyunsaturated fatty acids in cholesteryl esters and significantly lower C20:5 omega 3 in serum cholesteryl esters and phospholipids than minor depressed subjects and healthy controls. These findings suggest an abnormal intake or metabolism of essential fatty acids in conjunction with decreased formation of cholesteryl esters in major depression.

  11. Mapping the average AGN accretion rate in the SFR-M* plane for Herschel-selected galaxies at 0 < z ≤ 2.5

    NASA Astrophysics Data System (ADS)

    Delvecchio, I.; Lutz, D.; Berta, S.; Rosario, D. J.; Zamorani, G.; Pozzi, F.; Gruppioni, C.; Vignali, C.; Brusa, M.; Cimatti, A.; Clements, D. L.; Cooray, A.; Farrah, D.; Lanzuisi, G.; Oliver, S.; Rodighiero, G.; Santini, P.; Symeonidis, M.

    2015-05-01

    We study the relation of AGN accretion, star formation rate (SFR) and stellar mass (M*) using a sample of ≈8600 star-forming galaxies up to z = 2.5 selected with Herschel imaging in the GOODS and COSMOS fields. For each of them we derive SFR and M*, both corrected, when necessary, for emission from an active galactic nucleus (AGN), through the decomposition of their spectral energy distributions (SEDs). About 10 per cent of the sample are detected individually in Chandra observations of the fields. For the rest of the sample, we stack the X-ray maps to get average X-ray properties. After subtracting the X-ray luminosity expected from star formation and correcting for nuclear obscuration, we derive the average AGN accretion rate for both detected sources and stacks, as a function of M*, SFR and redshift. The average accretion rate correlates with SFR and with M*. The dependence on SFR becomes progressively more significant at z > 0.8. This may suggest that SFR is the original driver of these correlations. We find that average AGN accretion and star formation increase in a similar fashion with offset from the star-forming `main-sequence'. Our interpretation is that accretion on to the central black hole and star formation broadly trace each other, irrespective of whether the galaxy is evolving steadily on the main-sequence or bursting.

  12. Constraints on Feedback in the Local Universe: The Relation Between Star Formation and AGN Activity in Early Type Galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher P.; Baum, Stefi Alison

    2016-01-01

    We address the relation between star formation and AGN activity in a sample of 231 nearby (0.0002 < z < 0.0358) early type galaxies by carrying out a multi-wavelength study using archival observations in the UV, IR and radio. Our results indicate that early type galaxies in the current epoch are rarely powerful AGNs, with P < 1022 WHz-1 for a majority of the galaxies. Only massive galaxies are capable of hosting powerful radio sources while less massive galaxies are hosts to lower radio power sources. Evidence of ongoing star formation is seen in approximately 7% of the sample. The SFR of these galaxies is less than 0.1 M⊙yr-1. They also tend to be radio faint (P < 1022 WHz-1). There is a nearly equal fraction of star forming galaxies in radio faint (P < 1022 WHz-1) and radio bright galaxies (P ≥ 1022 WHz-1) suggesting that both star formation and radio mode feedback are constrained to be very low in our sample. We notice that our galaxy sample and the Brightest Cluster Galaxies (BCGs) follow similar trends in radio power versus SFR. This may be produced if both radio power and SFR are related to stellar mass.

  13. The isoflavone-rich fraction of the crude extract of the Puerariae flower increases oxygen consumption and BAT UCP1 expression in high-fat diet-fed mice.

    PubMed

    Kamiya, Tomoyasu; Nagamine, Rika; Sameshima-Kamiya, Mayu; Tsubata, Masahito; Ikeguchi, Motoya; Takagaki, Kinya

    2012-08-12

    Puerariae flower extract (PFE) is a crude extract of the Kudzu flower. Previous studies have shown that PFE supplementation exerts anti-obesity and anti-fatty liver effects in high-fat diet-fed mice. In this study, we aimed to identify the PFE components responsible for these effects and to determine their influence on energy expenditure and uncoupling protein 1 (UCP1) expression. Experiments were conducted on C57BL/6J male mice classified into 3 groups: (1) high-fat diet-fed (HFD), (2) high-fat diet-fed given PFE (HFD + PFE), and (3) high-fat diet-fed given the PFE isoflavone-rich fraction (HFD + ISOF). All groups were fed for 42 days. The HFD + PFE and HFD + ISOF groups showed significant resistance to increases in body weight, hepatic triglyceride level, and visceral fat compared to the HFD group. These groups also exhibited significant increases in oxygen consumption and UCP1-positive brown adipose tissue (BAT) area. Our results demonstrate that the active ingredients in PFE are present in the ISOF and that these compounds may increase energy expenditure by upregulation of BAT UCP1 expression. These findings provide valuable information regarding the anti-obesity effects of isoflavones.

  14. Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

    NASA Astrophysics Data System (ADS)

    Ballantyne, David R.

    2017-01-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z~5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z≈0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z≈0.9 quasars may be commonly hosted by haloes with Mh ~ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

  15. AGN are cooler than you think: the intrinsic far-IR emission from QSOs

    NASA Astrophysics Data System (ADS)

    Symeonidis, M.; Giblin, B. M.; Page, M. J.; Pearson, C.; Bendo, G.; Seymour, N.; Oliver, S. J.

    2016-06-01

    We present an intrinsic AGN spectral energy distribution (SED) extending from the optical to the submm, derived with a sample of unobscured, optically luminous (νLν,5100 > 1043.5 erg s-1) QSOs at z < 0.18 from the Palomar Green survey. The intrinsic AGN SED was computed by removing the contribution from stars using the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature in the QSOs' mid-IR spectra; the 1σ uncertainty on the SED ranges between 12 and 45 per cent as a function of wavelength and is a combination of PAH flux measurement errors and the uncertainties related to the conversion between PAH luminosity and star-forming luminosity. Longwards of 20 μm, the shape of the intrinsic AGN SED is independent of the AGN power indicating that our template should be applicable to all systems hosting luminous AGN (νLν, 5100 or L_X(2-10 keV) ≳ 1043.5 erg s-1). We note that for our sample of luminous QSOs, the average AGN emission is at least as high as, and mostly higher than, the total stellar powered emission at all wavelengths from the optical to the submm. This implies that in many galaxies hosting powerful AGN, there is no `safe' broad-band photometric observation (at λ < 1000 μm) which can be used in calculating star formation rates without subtracting the AGN contribution. Roughly, the AGN contribution may be ignored only if the intrinsic AGN luminosity at 5100 AA is at least a factor of 4 smaller than the total infrared luminosity (LIR, 8-1000 μm) of the galaxy. Finally, we examine the implication of our work in statistical studies of star formation in AGN host galaxies.

  16. The VIMOS Public Extragalactic Redshift Survey (VIPERS). A support vector machine classification of galaxies, stars, and AGNs

    NASA Astrophysics Data System (ADS)

    Małek, K.; Solarz, A.; Pollo, A.; Fritz, A.; Garilli, B.; Scodeggio, M.; Iovino, A.; Granett, B. R.; Abbas, U.; Adami, C.; Arnouts, S.; Bel, J.; Bolzonella, M.; Bottini, D.; Branchini, E.; Cappi, A.; Coupon, J.; Cucciati, O.; Davidzon, I.; De Lucia, G.; de la Torre, S.; Franzetti, P.; Fumana, M.; Guzzo, L.; Ilbert, O.; Krywult, J.; Le Brun, V.; Le Fevre, O.; Maccagni, D.; Marulli, F.; McCracken, H. J.; Paioro, L.; Polletta, M.; Schlagenhaufer, H.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Burden, A.; Di Porto, C.; Marchetti, A.; Marinoni, C.; Mellier, Y.; Moscardini, L.; Nichol, R. C.; Peacock, J. A.; Percival, W. J.; Phleps, S.; Wolk, M.; Zamorani, G.

    2013-09-01

    Aims: The aim of this work is to develop a comprehensive method for classifying sources in large sky surveys and to apply the techniques to the VIMOS Public Extragalactic Redshift Survey (VIPERS). Using the optical (u∗,g',r',i') and near-infrared (NIR) data (z', Ks), we develop a classifier, based on broad-band photometry, for identifying stars, active galactic nuclei (AGNs), and galaxies, thereby improving the purity of the VIPERS sample. Methods: Support vector machine (SVM) supervised learning algorithms allow the automatic classification of objects into two or more classes based on a multidimensional parameter space. In this work, we tailored the SVM to classifying stars, AGNs, and galaxies and applied this classification to the VIPERS data. We trained the SVM using spectroscopically confirmed sources from the VIPERS and VVDS surveys. Results: We tested two SVM classifiers and concluded that including NIR data can significantly improve the efficiency of the classifier. The self-check of the best optical + NIR classifier has shown 97% accuracy in the classification of galaxies, 97% for stars, and 95% for AGNs in the 5-dimensional colour space. In the test of VIPERS sources with 99% redshift confidence, the classifier gives an accuracy equal to 94% for galaxies, 93% for stars, and 82% for AGNs. The method was applied to sources with low-quality spectra to verify their classification, hence increasing the security of measurements for almost 4900 objects. Conclusions: We conclude that the SVM algorithm trained on a carefully selected sample of galaxies, AGNs, and stars outperforms simple colour-colour selection methods and can be regarded as a very efficient classification method particularly suitable for modern large surveys. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programme 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint

  17. Extinction Correction Significantly Influences the Estimate of the Lyα Escape Fraction

    NASA Astrophysics Data System (ADS)

    An, Fang Xia; Zheng, Xian Zhong; Hao, Cai-Na; Huang, Jia-Sheng; Xia, Xiao-Yang

    2017-02-01

    The Lyα escape fraction is a key measure to constrain the neutral state of the intergalactic medium and then to understand how the universe was fully reionized. We combine deep narrowband imaging data from the custom-made filter NB393 and the {{{H}}}2S1 filter centered at 2.14 μm to examine the Lyα emitters and Hα emitters at the same redshift z = 2.24. The combination of these two populations allows us to determine the Lyα escape fraction at z = 2.24. Over an area of 383 arcmin2 in the Extended Chandra Deep Field South (ECDFS), 124 Lyα emitters are detected down to NB393 = 26.4 mag at the 5σ level, and 56 Hα emitters come from An et al. Of these, four have both Lyα and Hα emissions (LAHAEs). We also collect the Lyα emitters and Hα emitters at z = 2.24 in the COSMOS field from the literature, and increase the number of LAHAEs to 15 in total. About one-third of them are AGNs. We measure the individual/volumetric Lyα escape fraction by comparing the observed Lyα luminosity/luminosity density to the extinction-corrected Hα luminosity/luminosity density. We revisit the extinction correction for Hα emitters using the Galactic extinction law with color excess for nebular emission. We also adopt the Calzetti extinction law together with an identical color excess for stellar and nebular regions to explore how the uncertainties in extinction correction affect the estimate of individual and global Lyα escape fractions. In both cases, an anti-correlation between the Lyα escape fraction and dust attenuation is found among the LAHAEs, suggesting that dust absorption is responsible for the suppression of the escaping Lyα photons. However, the estimated Lyα escape fraction of individual LAHAEs varies by up to ∼3 percentage points between the two methods of extinction correction. We find the global Lyα escape fraction at z = 2.24 to be (3.7 ± 1.4)% in the ECDFS. The variation in the color excess of the extinction causes a discrepancy of ∼1 percentage

  18. Suzaku View of the Swift/BAT Active Galactic Nuclei (I): Spectral Analysis of Six AGNs and Evidence for Two Types of Obscured Population

    NASA Technical Reports Server (NTRS)

    Eguchi, Satoshi; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tueller, Jack

    2009-01-01

    We present a systematic spectral analysis with Suzaku of six AGNs detected in the Swift/BAT hard X-ray (15-200 keV) survey, Swift J0138.6-4001, J0255.2-0011, J0350.1-5019, J0505.7-2348, J0601.9-8636, and J1628.1-5145. This is considered to be a representative sample of new AGNs without X-ray spectral information before the BAT survey. We find that the 0.5-200 keV spectra of these sources can be uniformly fit with a base model consisting of heavily absorbed (log NH >23.5/sq cm) transmitted components, scattered lights, a reflection component, and an iron-K emission line. There are two distinct groups, three "new type" AGNs (including the two sources reported by Ueda et al. 2007) with an extremely small scattered fraction (f(sub scat) < 0:5%) and strong reflection component (R = omega/2pi > or equal to 0.8 where omega is the solid angle of the reflector), and three "classical type" ones with f(sub scat > 0.5% and R < or approx. 0.8. The spectral parameters suggest that the new type has an optically thick torus for Thomson scattering (N(sub H) approx. 10(exp 25)/sq cm) with a small opening angle theta approx. 20deg viewed in a rather face-on geometry, while the classical type has a thin torus (N(sub H) approx. 10(exp 23-24)/sq cm) with theta > or approx. 30deg. We infer that a significant number of new type AGNs with an edge-on view is missing in the current all-sky hard X-ray surveys. Subject headings: galaxies: active . gamma rays: observations . X-rays: galaxies . X-rays: general

  19. Modelling the cosmological co-evolution of supermassive black holes and galaxies - I. BH scaling relations and the AGN luminosity function

    NASA Astrophysics Data System (ADS)

    Marulli, Federico; Bonoli, Silvia; Branchini, Enzo; Moscardini, Lauro; Springel, Volker

    2008-04-01

    We model the cosmological co-evolution of galaxies and their central supermassive black holes (BHs) within a semi-analytical framework developed on the outputs of the Millennium Simulation. This model, described in detail by Croton et al. and De Lucia and Blaizot, introduces a `radio mode' feedback from active galactic nuclei (AGN) at the centre of X-ray emitting atmospheres in galaxy groups and clusters. Thanks to this mechanism, the model can simultaneously explain: (i) the low observed mass dropout rate in cooling flows; (ii) the exponential cut-off in the bright end of the galaxy luminosity function and (iii) the bulge-dominated morphologies and old stellar ages of the most massive galaxies in clusters. This paper is the first of a series in which we investigate how well this model can also reproduce the physical properties of BHs and AGN. Here we analyse the scaling relations, the fundamental plane and the mass function of BHs, and compare them with the most recent observational data. Moreover, we extend the semi-analytic model to follow the evolution of the BH mass accretion and its conversion into radiation, and compare the derived AGN bolometric luminosity function with the observed one. While we find for the most part a very good agreement between predicted and observed BH properties, the semi-analytic model underestimates the number density of luminous AGN at high redshifts, independently of the adopted Eddington factor and accretion efficiency. However, an agreement with the observations is possible within the framework of our model, provided it is assumed that the cold gas fraction accreted by BHs at high redshifts is larger than at low redshifts.

  20. Hard X-ray Spectroscopy of Obscured AGN with NuSTAR

    NASA Astrophysics Data System (ADS)

    Balokovic, Mislav; Harrison, Fiona; NuSTAR Extragalactic Surveys Team

    2017-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) has enabled studies of the local active galactic nuclei (AGN) to extend into the hard X-ray band, up to 79 keV, with unprecedented spatial resolution and sensitivity. As a part of its extragalactic program, NuSTAR is surveying the nearby population of AGN detected at hard X-ray energies by the Swift Burst Alert Telescope (Swift/BAT), selecting even the most obscured local AGN. I will highlight some of the results based on broadband X-ray spectroscopy of individual targets and present my work on the large representative sample of more than a hundred nearby obscured AGN, which constitutes the largest available atlas of hard X-ray spectra of obscured AGN to date. The high quality of the data allows us to probe the details of AGN structures such as the X-ray-emitting corona and the toroidal obscurer in the under-explored spectral window above 10 keV. I will present both phenomenological results important for synthesis models of the cosmic X-ray background, and a novel approach for constraining the geometry of the gas surrounding the supermassive black hole (including the accretion disk, the broad-line region, and the torus) from the hard X-ray band. Finally, I will discuss how what we learned from this survey of local AGN relates to deeper high-redshift X-ray surveys and AGN structure probes at other wavelengths.

  1. Unravelling the Complex Structure of AGN-driven Outflows. II. Photoionization and Energetics

    NASA Astrophysics Data System (ADS)

    Karouzos, Marios; Woo, Jong-Hak; Bae, Hyun-Jin

    2016-12-01

    Outflows have been shown to be prevalent in galaxies hosting luminous active galactic nuclei (AGNs); they present a physically plausible way to couple the AGN energy output with the interstellar medium of their hosts. Despite their prevalence, accurate characterization of these outflows has been challenging. In the second of a series of papers, we use Gemini Multi-Object Spectrograph integral field unit (IFU) data of six local (z < 0.1) and moderate-luminosity Type 2 AGNs to study the ionization properties and energetics of AGN-driven outflows. We find strong evidence connecting the extreme kinematics of the ionized gas to the AGN photoionization. The kinematic component related to the AGN-driven outflow is clearly separated from other kinematic components, such as virial motions or rotation, on the velocity and velocity dispersion diagram. Our spatially resolved kinematic analysis reveals that 30 to 90% of the total mass and kinetic energy of the outflow is contained within the central kpc of the galaxy. The spatially integrated mass and kinetic energy of the gas entrained in the outflow correlate well with the AGN bolometric luminosity and results in energy conversion efficiencies between 0.01% and 1%. Intriguingly, we detect ubiquitous signs of ongoing circumnuclear star formation. Their small size, the centrally contained mass and energy, and the universally detected circumnuclear star formation cast doubts on the potency of these AGN-driven outflows as agents of galaxy-scale negative feedback.

  2. Submillimetre observations of WISE-selected high-redshift, luminous AGN and their surrounding overdense environments

    NASA Astrophysics Data System (ADS)

    Jones, Suzy F.

    2016-08-01

    We present JCMT SCUBA-2 850 μm submillimetre (submm) observations of 10 mid-infrared (mid-IR) luminous active galactic nuclei (AGNs), detected by the Wide-field Infrared Survey Explorer (WISE) all-sky IR survey and 30 that have also been detected by the NVSS/FIRST radio survey. These rare sources are selected by their extremely red mid-IR spectral energy distributions (SEDs). Further investigations show that they are highly obscured, have abundant warm AGN-heated dust and are thought to be experiencing intense AGN feedback. When comparing the number of submm galaxies detected serendipitously in the surrounding 1.5 arcmin to those in blank-field submm surveys, there is a very significant overdensity, of order 3-5, but no sign of radial clustering centred at our primary objects. The WISE-selected AGN thus reside in 10-Mpc-scale overdense environments that could be forming in pre-viralized clusters of galaxies. WISE-selected AGNs appear to be the strongest signposts of high-density regions of active, luminous and dusty galaxies. SCUBA-2 850 μm observations indicate that their submm fluxes are low compared to many popular AGN SED templates, hence the WISE/radio-selected AGNs have either less cold and/or more warm dust emission than normally assumed for typical AGN. Most of the targets have total IR luminosities ≥1013 L⊙, with known redshifts of 20 targets between z ˜ 0.44-4.6.

  3. A Search for AGN Intra-Day Variability with KVN

    NASA Astrophysics Data System (ADS)

    Lee, Taeseok; Trippe, Sascha; Oh, Junghwan; Byun, Do-Young; Sohn, Bong-Won; Lee, Sang-Sung

    2015-10-01

    Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a "anti-correlated" mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to assess the levels of variability and the corresponding upper limits. We found upper limits on flux variability ranging from ∼1.6% to ∼7.6%. The upper limits on the derived brightness temperatures exceed the inverse Compton limit by three to six orders of magnitude. From our results, plus comparison with data obtained by the University of Michigan Radio Astronomy Observatory, we conclude that we have not detected source-intrinsic variability which would have to occur at sub-per cent levels.

  4. Relativistic HD and MHD modelling for AGN jets

    NASA Astrophysics Data System (ADS)

    Keppens, R.; Porth, O.; Monceau-Baroux, R.; Walg, S.

    2013-12-01

    Relativistic hydro and magnetohydrodynamics (MHD) provide a continuum fluid description for plasma dynamics characterized by shock-dominated flows approaching the speed of light. Significant progress in its numerical modelling emerged in the last two decades; we highlight selected examples of modern grid-adaptive, massively parallel simulations realized by our open-source software MPI-AMRVAC (Keppens et al 2012 J. Comput. Phys. 231 718). Hydrodynamical models quantify how energy transfer from active galactic nuclei (AGN) jets to their surrounding interstellar/intergalactic medium (ISM/IGM) gets mediated through shocks and various fluid instability mechanisms (Monceau-Baroux et al 2012 Astron. Astrophys. 545 A62). With jet parameters representative for Fanaroff-Riley type-II jets with finite opening angles, we can quantify the ISM volumes affected by jet injection and distinguish the roles of mixing versus shock-heating in cocoon regions. This provides insight in energy feedback by AGN jets, usually incorporated parametrically in cosmological evolution scenarios. We discuss recent axisymmetric studies up to full 3D simulations for precessing relativistic jets, where synthetic radio maps can confront observations. While relativistic hydrodynamic models allow one to better constrain dynamical parameters like the Lorentz factor and density contrast between jets and their surroundings, the role of magnetic fields in AGN jet dynamics and propagation characteristics needs full relativistic MHD treatments. Then, we can demonstrate the collimating properties of an overal helical magnetic field backbone and study differences between poloidal versus toroidal field dominated scenarios (Keppens et al 2008 Astron. Astrophys. 486 663). Full 3D simulations allow one to consider the fate of non-axisymmetric perturbations on relativistic jet propagation from rotating magnetospheres (Porth 2013 Mon. Not. R. Astron. Soc. 429 2482). Self-stabilization mechanisms related to the detailed

  5. BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission

    NASA Astrophysics Data System (ADS)

    Lamperti, Isabella; Koss, Michael; Trakhtenbrot, Benny; Schawinski, Kevin; Ricci, Claudio; Oh, Kyuseok; Landt, Hermine; Riffel, Rogério; Rodríguez-Ardila, Alberto; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Mushotzky, Richard; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain

    2017-01-01

    We provide a comprehensive census of the near-Infrared (NIR, 0.8-2.4 μm) spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei (AGN), selected in the hard X-ray band (14-195 keV) from the Swift-Burst Alert Telescope (BAT) survey. With the launch of the James Webb Space Telescope this regime is of increasing importance for dusty and obscured AGN surveys. We measure black hole masses in 68% (69/102) of the sample using broad emission lines (34/102) and/or the velocity dispersion of the Ca II triplet or the CO band-heads (46/102). We find that emission line diagnostics in the NIR are ineffective at identifying bright, nearby AGN galaxies because ([Fe II] 1.257μm/Paβ and H2 2.12μm/Brγ) identify only 25% (25/102) as AGN with significant overlap with star forming galaxies and only 20% of Seyfert 2 have detected coronal lines (6/30). We measure the coronal line emission in Seyfert 2 to be weaker than in Seyfert 1 of the same bolometric luminosity suggesting obscuration by the nuclear torus. We find that the correlation between the hard X-ray and the [Fe II] coronal line luminosity is significantly better than with the [O III] λ5007 luminosity. Finally, we find 3/29 galaxies (10%) that are optically classified as Seyfert 2 show broad emission lines in the NIR. These AGN have the lowest levels of obscuration among the Seyfert 2s in our sample (log NH < 22.43 cm-2), and all show signs of galaxy-scale interactions or mergers suggesting that the optical broad emission lines are obscured by host galaxy dust.

  6. The AGN Jet Model of the Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Guo, Fulai

    2017-01-01

    The nature and origin of the Fermi bubbles detected in the inner Galaxy remain elusive. In this paper, we briefly discuss some recent theoretical and observational developments, with a focus on the AGN jet model. Analogous to radio lobes observed in massive galaxies, the Fermi bubbles could be naturally produced by a pair of opposing jets emanating nearly along the Galaxy's rotation axis from the Galactic center. Our two-fluid hydrodynamic simulations reproduce quite well the bubble location and shape, and interface instabilities at the bubble surface could be effectively suppressed by shear viscosity. We briefly comment on some potential issues related to our model, which may lead to future progress.

  7. Characterizing X-ray Variability Processes in AGN

    NASA Astrophysics Data System (ADS)

    Markowitz, A.

    2006-07-01

    We comment on searches for characteristic X-ray variability time- scales in the red-noise light curves of Active Galactic Nuclei (AGN). Methods for identification of such features and determining their statistical significance are discussed. Pros and cons of two common tools, the power spectral density function (PSD) and the structure function (SF), are reviewed. Caveats associated with identification of quasi-periodic oscillations (QPOs) in the presence of red-noise variability are also discussed. A central point of this paper is to make all readers aware that there already exist good references out there for determining the statistical significance of claims of characteristic variability time scales.

  8. The KMOS AGN Survey at High redshift (KASHz): the prevalence and drivers of ionized outflows in the host galaxies of X-ray AGN

    NASA Astrophysics Data System (ADS)

    Harrison, C. M.; Alexander, D. M.; Mullaney, J. R.; Stott, J. P.; Swinbank, A. M.; Arumugam, V.; Bauer, F. E.; Bower, R. G.; Bunker, A. J.; Sharples, R. M.

    2016-02-01

    We present the first results from the KMOS (K-band Multi-Object Spectrograph) AGN (active galactic nuclei) Survey at High redshift (KASHz), a VLT/KMOS integral-field spectroscopic (IFS) survey of z ≳ 0.6 AGN. We present galaxy-integrated spectra of 89 X-ray AGN (L2-10 keV = 1042-1045 erg s-1), for which we observed [O III] (z ≈ 1.1-1.7) or Hα emission (z ≈ 0.6-1.1). The targets have X-ray luminosities representative of the parent AGN population and we explore the emission-line luminosities as a function of X-ray luminosity. For the [O III] targets, ≈50 per cent have ionized gas velocities indicative of gas that is dominated by outflows and/or highly turbulent material (i.e. overall line widths ≳600 km s-1). The most luminous half (i.e. LX > 6 × 1043 erg s-1) have a ≳2 times higher incidence of such velocities. On the basis of our results, we find no evidence that X-ray obscured AGN are more likely to host extreme kinematics than unobscured AGN. Our KASHz sample has a distribution of gas velocities that is consistent with a luminosity-matched sample of z < 0.4 AGN. This implies little evolution in the prevalence of ionized outflows, for a fixed AGN luminosity, despite an order-of-magnitude decrease in average star formation rates over this redshift range. Furthermore, we compare our Hα targets to a redshift-matched sample of star-forming galaxies and despite a similar distribution of Hα luminosities and likely star formation rates, we find extreme ionized gas velocities are up to ≈10 times more prevalent in the AGN-host galaxies. Our results reveal a high prevalence of extreme ionized gas velocities in high-luminosity X-ray AGN and imply that the most powerful ionized outflows in high-redshift galaxies are driven by AGN activity.

  9. The central engine of quasars and AGNs - Scaling to solar mass black holes

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1988-01-01

    The model of the previous paper (Ellison and Kazanas, hereafter EK) can be readily scaled to model systems with black holes 3-10 solar masses, such as those expected to exist in certain Galactic X-ray binaries. The model can account in a straightforward way for the bimodal behavior of Cyg X-1 and the other Galactic black hole candidates (White and Marshall 1984; White, et al., 1984). It is argued that the change in the spectrum with luminosity is due to the drastic increase of both the source compactness and luminosity with small changes in the accretion rate, and conversion of most of the energy into electron-positron pairs which render the source optically thick and modify its spectrum. It is also argued that similar effects may be observed in AGNs.

  10. Optically Elusive AGN in the 3XMM Catalog and the Chandra-COSMOS field

    NASA Astrophysics Data System (ADS)

    Pons, Estelle; Watson, Mike; Elvis, Martin; Civano, Francesca M.

    2015-01-01

    'Optically elusive AGN' are powerful X-ray sources (LHX > 1042 erg/s), but are not detected as AGN in the optical. Pons and Watson (2014) showed that in XMM these AGNs are a mix of Narrow Line Seyfert 1s, True Seyfert 2's and weak Seyfert 2s. The nature of these objects, coming from the cross-match of 3XMM with the SDSS-DR9 spectroscopic catalog, has been investigated through a detailed analysis of their IR/optical and X-ray properties. The fainter Chandra-COSMOS field should be rich in optically elusive AGNs as ¾ of the AGNs there are narrow-lined. There are ~850 Chandra-COSMOS galaxy spectra, mainly from five different telescopes (SDSS, Magellan, MMT, VLT and Keck). To find optically elusive objects, we investigate the optical classification using emission line diagnostic diagrams. For low redshift galaxies (z~<0.7) the standard BPT diagram ([OIII

  11. A complete hard X-ray selected sample of local, luminous AGNs

    NASA Astrophysics Data System (ADS)

    Burtscher, Leonard; Davies, Ric; Lin, Ming-yi; Orban de Xivry, Gilles; Rosario, David

    2016-08-01

    Choosing a very well defined sample is essential for studying the AGN phenomenon. Only the most luminous AGNs can be expected to require a coherent feeding mechanism to sustain their activity and since host galaxy properties and AGN activity are essentially uncorrelated, nuclear scales must be resolved in order to shed light on the feeding mechanisms of AGNs. For these reasons we are compiling a sample of the most powerful, local AGNs. In this talk we present our on-going programme to observe a complete volume limited sample of nearby active galaxies selected by their 14-195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow.

  12. Quantifying the impact of AGN and nebular emission on stellar population properties with REBETIKO

    NASA Astrophysics Data System (ADS)

    Cardoso, L. S. M.; Gomes, J. M.; Papaderos, P.

    2016-06-01

    Spectral synthesis enables the reconstruction of the star formation and chemical evolution histories (SFH & CEH) of a galaxy that are encoded in its spectral energy distribution (SED). Most state-of-the-art population synthesis codes however consider only purely stellar emission and are hence inadequate for modelling studies of galaxies where non-stellar emission components contribute significantly to the SED. This work combines evolutionary and population synthesis techniques to quantify the impact of active galactic nucleus (AGN) and nebular emission on the determination of the stellar population properties in galaxies. We have developed an evolutionary synthesis code called REBETIKO - Reckoning galaxy Emission By means of Evolutionary Tasks with Input Key Observables - to compute and study the time evolution of the SED of AGN-hosts and starburst galaxies. Our code takes into account the main ingredients of a galaxy's SED (e.g. non-thermal emission and/or nebular continuum and lines) for various commonly used parameterizations of the SFH, such as instantaneous burst, constant, exponentially decreasing, and gradually increasing peaking at a redshift between 1-10. Synthetic SEDs computed with REBETIKO have been subsequently fitted with the STARLIGHT population synthesis code (PSC) which can be regarded as representative for currently available state-of-the-art (i.e. purely stellar) PSCs. The objective is to study the impact of non-stellar SED components on the recovery of the true total stellar mass M_{star} and SFH of a galaxy, as well as other evolutionary properties, such as CEH and light- and mass-weighted mean stellar age and metallicity. We find that purely stellar fits in galaxies with a strong non-stellar continuum (e.g. Seyfert and/or starburst galaxies) can for instance overestimate M_{star} by up to 3 orders of magnitude, while the mean stellar age and metallicity can deviate from their true values up to 2 and 4 dex, respectively. These results imply

  13. A Herschel Study of 24 μμm-Selected AGNs and Their Host Galaxies

    NASA Astrophysics Data System (ADS)

    Xu, Lei; Rieke, G. H.; Egami, E.; Pereira, M. J.; Haines, C. P.; Smith, G. P.

    2015-08-01

    We present a sample of 290 24 μm-selected active galactic nuclei (AGNs) mostly at z ˜ 0.3-2.5, within 5.2 {{deg}}2 distributed as 25\\prime × 25\\prime fields around each of 30 galaxy clusters in the Local Cluster Substructure Survey. The sample is nearly complete to 1 mJy at 24 μm, and has a rich multiwavelength set of ancillary data; 162 are detected by Herschel. We use spectral templates for AGNs, stellar populations, and infrared (IR) emission by star-forming galaxies to decompose the spectral energy distributions (SEDs) of these AGNs and their host galaxies, and estimate their star formation rates, AGN luminosities, and host galaxy stellar masses. The set of templates is relatively simple: a standard Type-1 quasar template; another for the photospheric output of the stellar population; and a far-infrared star-forming template. For the Type-2 AGN SEDs, we substitute templates including internal obscuration, and some Type-1 objects require a warm component (T≳ 50 K). The individually Herschel-detected Type-1 AGNs and a subset of 17 Type-2 AGNs typically have luminosities \\gt {10}45 {ergs} {{{s}}}-1, and supermassive black holes of ˜ 3× {10}8 {M}⊙ emitting at ˜10% of the Eddington rate. We find them in about twice the numbers of AGNs identified in SDSS data in the same fields, i.e., they represent typical high-luminosity AGNs, not an IR-selected minority. These AGNs and their host galaxies are studied further in an accompanying paper.

  14. Fractional random walk lattice dynamics

    NASA Astrophysics Data System (ADS)

    Michelitsch, T. M.; Collet, B. A.; Riascos, A. P.; Nowakowski, A. F.; Nicolleau, F. C. G. A.

    2017-02-01

    We analyze time-discrete and time-continuous ‘fractional’ random walks on undirected regular networks with special focus on cubic periodic lattices in n  =  1, 2, 3,.. dimensions. The fractional random walk dynamics is governed by a master equation involving fractional powers of Laplacian matrices {{L}\\fracα{2}}} where α =2 recovers the normal walk. First we demonstrate that the interval 0<α ≤slant 2 is admissible for the fractional random walk. We derive analytical expressions for the transition matrix of the fractional random walk and closely related the average return probabilities. We further obtain the fundamental matrix {{Z}(α )} , and the mean relaxation time (Kemeny constant) for the fractional random walk. The representation for the fundamental matrix {{Z}(α )} relates fractional random walks with normal random walks. We show that the matrix elements of the transition matrix of the fractional random walk exihibit for large cubic n-dimensional lattices a power law decay of an n-dimensional infinite space Riesz fractional derivative type indicating emergence of Lévy flights. As a further footprint of Lévy flights in the n-dimensional space, the transition matrix and return probabilities of the fractional random walk are dominated for large times t by slowly relaxing long-wave modes leading to a characteristic {{t}-\\frac{n{α}} -decay. It can be concluded that, due to long range moves of fractional random walk, a small world property is emerging increasing the efficiency to explore the lattice when instead of a normal random walk a fractional random walk is chosen.

  15. The faint radio AGN population in the spotlight

    NASA Astrophysics Data System (ADS)

    Herrera Ruiz, Noelia; Middelberg, Enno

    2016-08-01

    To determine the AGN component in the faint radio population is fundamental in galaxy evolution studies. A relatively easy and direct way to determine which galaxies do have a radio-active AGN is a detection using the Very Long Baseline Interferometry (VLBI) technique. The goal of this project is to study with statistically relevant numbers the faint radio source population using VLBI observations. To achieve this goal, the project is divided into two parts. In the first part, we have observed ~3000 radio sources in the COSMOS extragalactic field with the Very Long Baseline Array (VLBA) at 1.4GHz. We have detected 468 sources. In the second part, we have observed ~200 radio sources in the COSMOS field with extremely high sensitivity using the VLBA together with the Green Bank Telescope (GBT) at 1.4GHz, to explore an even fainter population in the flux density regime of tens of uJy. We are currently calibrating this data. In this overview I will present the survey design, observations, and calibration, along with some first results.

  16. XMM-Newton, powerful AGN winds and galaxy feedback

    NASA Astrophysics Data System (ADS)

    Pounds, K.; King, A.

    2016-06-01

    The discovery that ultra-fast ionized winds - sufficiently powerful to disrupt growth of the host galaxy - are a common feature of luminous AGN is major scientific breakthrough led by XMM-Newton. An extended observation in 2014 of the prototype UFO, PG1211+143, has revealed an unusually complex outflow, with distinct and persisting velocities detected in both hard and soft X-ray spectra. While the general properties of UFOs are consistent with being launched - at the local escape velocity - from the inner disc where the accretion rate is modestly super-Eddington (King and Pounds, Ann Rev Astron Astro- phys 2015), these more complex flows have raised questions about the outflow geometry and the importance of shocks and enhanced cooling. XMM-Newton seems likely to remain the best Observatory to study UFOs prior to Athena, and further extended observations, of PG1211+143 and other bright AGN, have the exciting potential to establish the typical wind dynamics, while providing new insights on the accretion geometry and continuum source structure. An emphasis on such large, coordinated observing programmes with XMM-Newton over the next decade will continue the successful philosophy pioneered by EXOSAT, while helping to inform the optimum planning for Athena

  17. AGN-Induced Cavities in NGC 1399 And NGC 4649

    SciTech Connect

    Shurkin, K.; Dunn, R.J.H.; Gentile, G.; Taylor, G.B.; Allen, S.W.; /KIPAC, Menlo Park

    2007-11-14

    We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC1399 and the E2 galaxy NGC4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required for the AGN to evacuate these cavities and find values of {approx} 8x10{sup 41} erg s-1 and {approx} 14x10{sup 41} erg s{sup -1} for the lobes of NGC1399 and {approx} 7x10{sup 41} erg s{sup -1} and {approx} 6x1041 erg s{sup -1} for those of NGC4649. We also calculate the k/f values for each cavity, where k is the ratio of the total particle energy to that of electrons radiating in the range of 10 MHz to 10 GHz, and f is the volume filling factor of the plasma in the cavity. We find that the values of k/f for the lobes of NGC1399 are {approx} 93 and {approx} 190, and those of the lobes of NGC4649 are {approx} 15000 and {approx} 12000. We conclude that the assumed spectrum describes the electron distribution in the lobes of NGC1399 reasonably well, and that there are few entrained particles. For NGC4649, either there are many entrained particles or the model spectrum does not accurately describe the population of electrons.

  18. An AGN Identification for 3EG J2006-2321

    NASA Technical Reports Server (NTRS)

    Wallace, P. M.; Halpern, J. P.; Magalhaes, A. M.; Thompson, D. J.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    We present a multiwavelength analysis of the high-energy gamma-ray source 3EG J2006-2321 (l = 18 deg.82, b = -26 deg.26). The flux of this source above 100 MeV is shown to be variable on time scales of days and months. Optical observations and careful examination of archived radio data indicate that its most probable identification is with PMN J2005-2310, a flat-spectrum radio quasar with a 5GHz flux density of 260 mJy. Study of the V = 19.3 optical counterpart indicates a redshift of 0.833 and variable linear polarization. No X-ray source has been detected near the position of PMN J2005-2310, but an X-ray upper limit is derived from ROSAT data. This upper limit provides for a spectral energy distribution with global characteristics similar to those of known gamma-ray blazars. Taken together, these data indicate that 3EG J2006-2321, listed as unidentified in the 3rd EGRET Catalog, is a member of the blazar class of AGN. The 5-GHz radio flux density of this blazar is the lowest of the 68 EGRET-detected AGN. The fact that EGRET has detected such a source has implications for unidentified EGRET sources, particularly those at high latitudes (absolute value of b greater than 30 deg), many of which may be blazars.

  19. Fractional vector calculus and fractional Maxwell's equations

    SciTech Connect

    Tarasov, Vasily E.

    2008-11-15

    The theory of derivatives and integrals of non-integer order goes back to Leibniz, Liouville, Grunwald, Letnikov and Riemann. The history of fractional vector calculus (FVC) has only 10 years. The main approaches to formulate a FVC, which are used in the physics during the past few years, will be briefly described in this paper. We solve some problems of consistent formulations of FVC by using a fractional generalization of the Fundamental Theorem of Calculus. We define the differential and integral vector operations. The fractional Green's, Stokes' and Gauss's theorems are formulated. The proofs of these theorems are realized for simplest regions. A fractional generalization of exterior differential calculus of differential forms is discussed. Fractional nonlocal Maxwell's equations and the corresponding fractional wave equations are considered.

  20. The Origin of Double-peaked Narrow Lines in Active Galactic Nuclei. I. Very Large Array Detections of Dual AGNs and AGN Outflows

    NASA Astrophysics Data System (ADS)

    Müller-Sánchez, F.; Comerford, J. M.; Nevin, R.; Barrows, R. S.; Cooper, M. C.; Greene, J. E.

    2015-11-01

    We have examined a subset of 18 active galactic nuclei (AGNs) drawn from a sample of 81 galaxies that possess double-peaked narrow optical emission line spectra in the Sloan Digital Sky Survey, have 2 optical AGN emission components separated by >0.″2, and are detected in the Faint Images of the Radio Sky at Twenty-centimeters survey. Without follow-up observations, the sources of the double-peaked narrow emission lines are uncertain, and may be produced by kiloparsec-scale separation dual active supermassive black holes, AGN outflows, or disk rotation. In this work, we propose a new methodology to characterize double-peaked narrow emission line galaxies based on optical long-slit spectroscopy and high-resolution multi-band Very Large Array observations. The nature of the radio emission in the sample galaxies is varied. Of the 18 galaxies, we detect 2 compact flat-spectrum radio cores with projected spatial separations on the sky between 0.6 and 1.6 kpc in 3 galaxies: J1023+3243, J1158+3231, and J1623+0808. The two radio sources are spatially coincident with the two optical components of ionized gas with AGN-like line ratios, which confirms the presence of dual AGNs in these three galaxies. Dual AGNs account for only ∼15% (3/18) of the double-peaked AGNs in our sample. Gas kinematics produce ∼75% (13/18) of the double-peaked narrow emission lines, distributed in the following way: seven AGN wind-driven outflows, five radio-jet driven outflows, and one rotating narrow-line region. The remaining 10% (2/18) are ambiguous cases. Our method demonstrates the power of spatially resolved spectroscopy and high-resolution radio observations for the identification of AGN outflows and AGN pairs with angular separations as small as 0.″18. Based on observations at the NRAO Karl G. Jansky VLA (program 12A-103).

  1. Investigating the AGN activity and black hole masses in low surface brightness galaxies

    NASA Astrophysics Data System (ADS)

    Subramanian, Smitha; Sethuram, Ramya; Das, Mousumi; George, Koshy; Thirupathi, Sivarani; Prabhu, Tushar P.

    2016-02-01

    We present an analysis of the optical nuclear spectra from the active galactic nuclei (AGN) in a sample of giant low surface brightness (GLSB) galaxies. GLSB galaxies are extreme late type spirals that are large, isolated and poorly evolved compared to regular spiral galaxies. Earlier studies have indicated that their nuclei have relatively low mass black holes. Using data from the Sloan Digital Sky Survey (SDSS), we selected a sample of 30 GLSB galaxies that showed broad Hα emission lines in their AGN spectra. In some galaxies such as UGC 6284, the broad component of Hα is more related to outflows rather than the black hole. One galaxy (UGC 6614) showed two broad components in Hα, one associated with the black hole and the other associated with an outflow event. We derived the nuclear black hole (BH) masses of 29 galaxies from their broad Hα parameters. We find that the nuclear BH masses lie in the range 105 - 107 M⊙. The bulge stellar velocity dispersion σ e was determined from the underlying stellar spectra. We compared our results with the existing BH mass - velocity dispersion (M BH-σ e ) correlations and found that the majority of our sample lie in the low BH mass regime and below the M BH-σ e correlation. The effects of galaxy orientation in the measurement of σ e and the increase of σ e due to the effects of bar are probable reasons for the observed offset for some galaxies, but in many galaxies the offset is real. A possible explanation for the M BH-σ e offset could be lack of mergers and accretion events in the history of these galaxies which leads to a lack of BH-bulge co-evolution.

  2. A search for X-ray reprocessing echoes in the power spectral density functions of AGN

    NASA Astrophysics Data System (ADS)

    Emmanoulopoulos, D.; Papadakis, I. E.; Epitropakis, A.; Pecháček, T.; Dovčiak, M.; McHardy, I. M.

    2016-09-01

    We present the results of a detailed study of the X-ray power spectral density (PSD) functions of 12 X-ray bright AGN, using almost all the archival XMM-Newton data. The total net exposure of the EPIC-pn light curves is larger than 350 ks in all cases (and exceeds 1 Ms in the case of 1H 0707-497). In a physical scenario in which X-ray reflection occurs in the inner part of the accretion disc of AGN, the X-ray reflection component should be a filtered echo of the X-ray continuum signal and should be equal to the convolution of the primary emission with the response function of the disc. Our primary objective is to search for these reflection features in the 5-7 keV (iron line) and 0.5-1 keV (soft) bands, where the X-ray reflection fraction is expected to be dominant. We fit to the observed periodograms two models: a simple bending power-law model (BPL) and a BPL model convolved with the transfer function of the accretion disc assuming the lamp-post geometry and X-ray reflection from a homogeneous disc. We do not find any significant features in the best-fitting BPL model residuals either in individual PSDs in the iron band, soft and full band (0.3-10 keV) or in the average PSD residuals of the brightest and more variable sources (with similar black hole mass estimates). The typical amplitude of the soft and full-band residuals is around 3-5 per cent. It is possible that the expected general relativistic effects are not detected because they are intrinsically lower than the uncertainty of the current PSDs, even in the strong relativistic case in which X-ray reflection occurs on a disc around a fast rotating black hole having an X-ray source very close above it. However, we could place strong constrains to the X-ray reflection geometry with the current data sets if we knew in advance the intrinsic shape of the X-ray PSDs, particularly its high-frequency slope.

  3. FUSE Survey of Interstellar Molecular Hydrogen Toward 45 High-Latitude AGN

    NASA Astrophysics Data System (ADS)

    Gillmon, K.; Shull, J. M.; Danforth, C.; Tumlinson, J.

    2006-06-01

    We report results from a Far Ultraviolet Spectroscopic Explorer (FUSE) survey of interstellar molecular hydrogen (H2) along 45 sightlines to background AGN at high Galactic latitudes (|b| > 20°). The high-latitude sightlines are effective at probing diffuse gas in the low Galactic halo, including large-scale gaseous structures. FUSE spectra of 87% (39 of 45) of the observed AGN show detectable Galactic H2 absorption from the Lyman and Werner bands between 920 and 1126 Å, with detected column densities ranging from N(H2)=1014.17-19.82 cm-2. Our survey is sensitive to N(H2)>1013.8-14.6 cm-2, depending on the S/N (2--11 per pixel) and spectral resolution (R=15,000-20,000). The broad range of column densities indicates large fluctuations in the spatial structure of high-latitude H2 clouds, particularly at b > 54°. In the northern hemisphere, we identify many regions of low N(H2) (≤ 1015 cm-2) between (l=60°-180° and b>54°). These ``H2 holes" may be related to the ``Northern Chimney" (region of low Na I absorption, Lallement et al. 2003) and the ``Lockman Hole" (region of low NHI, Lockman et al. 1986). A comparison of these high-latitude results with those from our FUSE survey of ˜130 OB-star sightlines in the Galactic disk suggests that that halo and disk clouds have different physical properties. The mean rotational temperature, < T01halo > = 125 ± 15 K, is higher than that found in the Galactic disk, < T01disk >= 86 ± 20 K. Because this H2 temperature is elevated compared to gas in the Milky Way disk (Savage et al. 1977; Shull et al. 2004) or in the LMC/SMC (Tumlinson et al. 2002), it may imply enhanced heating or reduced cooling rates in Galactic halo diffuse H2 clouds. The transition to appreciable molecular fractions, fH2 > 0.01, in our halo sample occurs at a lower total hydrogen column density (log NHhalo = 20.35) than in the Galactic disk (log NHdisk = 20.7), possibly indicating reduced H2 photodissociation rates offsetting a lower formation rate on

  4. Initialized Fractional Calculus

    NASA Technical Reports Server (NTRS)

    Lorenzo, Carl F.; Hartley, Tom T.

    2000-01-01

    This paper demonstrates the need for a nonconstant initialization for the fractional calculus and establishes a basic definition set for the initialized fractional differintegral. This definition set allows the formalization of an initialized fractional calculus. Two basis calculi are considered; the Riemann-Liouville and the Grunwald fractional calculi. Two forms of initialization, terminal and side are developed.

  5. The ``entropy floor'' is porous - remarks on the coexistence of star formation and kinetic AGN feedback

    NASA Astrophysics Data System (ADS)

    Tremblay, Grant R.

    2014-07-01

    We discuss the morphology of star forming clouds and filaments in the central (<~ 50 kpc) regions of 16 low redshift (z<0.3) cool core brightest cluster galaxies (BCGs). The sample spans decades-wide ranges of X-ray mass deposition and star formation rates as well as active galactic nucleus (AGN) mechanical power, encompassing both high and low extremes of the supposed intracluster medium (ICM) cooling and AGN heating feedback cycle. Amid evidence that the gas fueling both star formation and AGN activity has condensed from the hot atmosphere, we present new and archival Hubble Space Telescope (HST) images of far ultraviolet (FUV) continuum emission directly associated with young stars, acting as a calorimeter for the degree to which the suppression of star formation by AGN mechanical feedback may be spatially or temporally inefficient. We discuss evidence for temporal and possibly cyclical variation in star formation rate, wherein elevated cooling episodes are permitted when AGN feedback is in a low-power state, and vice-versa. Several sources exhibit strong morphological evidence that low levels of star formation can survive and may indeed be triggered by the passage of a propagating radio source. We conclude by discussing the apparent coexistence of feedback and star formation. If AGN mechanical power does establish an ``entropy floor'', this floor must be porous, or raise and lower as the AGN varies in power.

  6. Binary Black Holes, Accretion Disks and Relativistic Jets: Photocenters of Nearby AGN and Quasars

    NASA Technical Reports Server (NTRS)

    Wehrle, Ann E.; Jones, Dayton L.; Meier, David L.; Piner, B. Glenn; Unwin, Stephen C.

    2004-01-01

    One of the most challenging questions in astronomy today is to understand the origin, structure, and evolution of the central engines in the nuclei of quasars and active galaxies (AGNs). The favoured theory involves the activation of relativistic jets from the fueling of a supermassive black hole through an accretion disk. In some AGN an outer optically thick, dusty torus is seen orbiting the black hole system. This torus is probably related to an inner accretion disk - black hole system that forms the actual powerhouse of the AGN. In radio-loud AGN two oppositely-directed radio jets are ejected perpendicular to the torus/disk system. Although there is a wealth of observational data on AGN, some very basic questions have not been definitively answered. The Space Interferometry Mission (SIM) will address the following three key questions about AGN. 1) Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? 2) Does the separation of the radio core and optical photocenter of the quasars used for the reference frame tie, change on the timescales of their photometric variability, or is the separation stable at the level of a few microarcseconds? 3) Do the cores of galaxies harbor binary supermassive black holes remaining from galaxy mergers? It is not known whether such mergers are common, and whether binaries would persist for a significant time.

  7. Towards an understanding of the Radio-mode AGN Feedback at higher redshifts

    NASA Astrophysics Data System (ADS)

    Bîrzan, Laura

    2015-08-01

    Direct evidence for feedback by active galactic nuclei (AGN) on the intra-cluster medium (ICM) of nearby groups and clusters has been provided by Chandra X-ray images. They show that the radio lobes emitted by the AGN create cavities in the hot cluster atmosphere, whichaffects the cooling gas that leads to star formation and galaxy growth and allow a direct measurement of the bulk of the AGN's power. Consequently, AGN feedback is now recognized as a necessary ingredient for galaxy formation models to prevent overcooling in massive halos. It is therefore important to study AGN feedback at redshifts where clusters are known to form (z ~ 1) and AGN feedback is predicted to regulate star formation in the most massive galaxies. Together with radio data, the cavities allow us to derive scaling relations that can be used to estimate the AGN feedback power using only radio data. I will review the importance of such relations for extending current studies of feedback with new and upcoming radio telescopes such as LOFAR and SKA, and I will present preliminary results from deep low-frequency LOFAR observations of the NEP field to understand if the local cooling-to-heating balance and the corresponding scaling relations (between jet power and radio luminosity) hold at these redshifts (z > 0.5).

  8. Tempered fractional calculus

    SciTech Connect

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-15

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  9. AGN Clustering in the Local Universe: An Unbiased Picture from Swift-BAT

    SciTech Connect

    Cappelluti, N.; Ajello, M.; Burlon, D.; Krumpe, M.; Miyaji, T.; Bonoli, S.; Greiner, J.; /Garching, Max Planck Inst., MPE

    2011-08-11

    We present the clustering measurement of hard X-ray selected AGN in the local Universe. We used a sample of 199 sources spectroscopically confirmed detected by Swift-BAT in its 15-55 keV all-sky survey. We measured the real space projected auto-correlation function and detected a signal significant on projected scales lower than 200 Mpc/h. We measured a correlation length of r{sub 0} = 5.56{sup +0.49}{sub -0.43} Mpc/h and a slope {gamma} = 1.64{sup -0.08}{sub -0.07}. We also measured the auto-correlation function of Tyep I and Type II AGN and found higher correlation length for Type I AGN. We have a marginal evidence of luminosity dependent clustering of AGN, as we detected a larger correlation length of luminous AGN than that of low luminosity sources. The corresponding typical host DM halo masses of Swift-BAT are {approx} log(M{sub DMH) {approx} 12-14 h{sup -1}M/M{sub {circle_dot}} which is the typical mass of a galaxy group. We estimated that the local AGN population has a typical lifetime {tau}{sub AGN} {approx}0.7 Gyr, it is powered by SMBH with mass M{sub BH} {approx}1-10x10{sup 8} M{sub {circle_dot}} and accreting with very low efficiency, log({epsilon}){approx}-2.0>. We also conclude that local AGN galaxies are typically red-massive galaxies with stellar mass of the order 2-80x10{sup 10} h{sup -1}M{sub {circle_dot}}. We compared our results with clustering predictions of merger-driven AGN triggering models and found a good agreement.

  10. Submillimetre observations of WISE/radio-selected AGN and their environments

    NASA Astrophysics Data System (ADS)

    Jones, Suzy F.; Blain, Andrew W.; Lonsdale, Carol; Condon, James; Farrah, Duncan; Stern, Daniel; Tsai, Chao-Wei; Assef, Roberto J.; Bridge, Carrie; Kimball, Amy; Lacy, Mark; Eisenhardt, Peter; Wu, Jingwen; Jarrett, Tom

    2015-04-01

    We present JCMT SCUBA-2 850 μm submillimetre (submm) observations of 30 mid-infrared (mid-IR) luminous active galactic nuclei (AGNs), detected jointly by the Wide-field Infrared Survey Explorer (WISE) all-sky IR survey and the NVSS/FIRST radio survey. These rare sources are selected by their extremely red mid-IR spectral energy distributions (SEDs) and compact radio counterparts. Further investigations show that they are highly obscured, have abundant warm AGN-heated dust and are thought to be experiencing intense AGN feedback. These galaxies appear to be consistent with a later AGN-dominated phase of merging galaxies, while hot, dust-obscured galaxies are an earlier starburst-dominated phase. When comparing the number of submm galaxies detected serendipitously in the surrounding 1.5 arcmin to those in blank-field submm surveys, there is a very significant overdensity, of order 5, but no sign of radial clustering centred at our primary objects. The WISE/radio-selected AGN thus reside in 10-Mpc-scale overdense environments that could be forming in pre-viralized clusters of galaxies. WISE/radio-selected AGNs appear to be the strongest signposts of high-density regions of active, luminous and dusty galaxies. SCUBA-2 850 μm observations indicate that their submm fluxes are low compared to many popular AGN SED templates, hence the WISE/radio-selected AGNs have either less cold and/or more warm dust emission than normally assumed for typical AGN. Most of the targets are not detected, only four targets are detected at SCUBA-2 850 μm, and have total IR luminosities ≥1013 L⊙, if their redshifts are consistent with the subset of the 10 SCUBA-2 undetected targets with known redshifts, z ˜ 0.44-2.86.

  11. Revealing the Evolving Accretion Disk Corona in AGNs with Multi-Epoch X-ray Spectroscopy: the case of Mrk 335

    NASA Astrophysics Data System (ADS)

    Ballantyne, David R.; Keek, Laurens

    2016-04-01

    Active galactic nuclei host an accretion disk with an X-ray producing corona around a supermassive black hole. In bright sources, such as the Seyfert 1 galaxy Mrk 335, reflection of the coronal emission off the accretion disk has been observed. Reflection produces numerous spectral features, such as the Fe Kα emission line and absorption edge, which allow various properties of the inner accretion disk and corona to be constrained. We perform a multi-epoch spectral analysis of a dozen XMM-Newton, Suzaku, and NuSTAR observations of Mrk 335, and optimize the fitting procedure to unveil correlations between the Eddington ratio and multiple spectral parameters. We find that the ionization parameter of the accretion disk correlates strongly with the Eddington ratio: the inner disk is more strongly ionized at higher flux. Interestingly, the slope of the correlation is less steep than previously predicted. Furthermore, the cut-off of the power-law spectrum increases in energy with the Eddington ratio, whereas the reflection fraction exhibits a decrease. We interpret this behaviour as geometrical changes of the corona as a function of the accretion rate. Below ~10% of the Eddington limit, the compact and optically thick corona is located close to the inner disk, whereas at higher accretion rates the corona is likely optically thin and extends vertically further away from the disk surface. Compared to previous work that considered individual spectra, we find that multi-epoch spectroscopy is essential for breaking degeneracies in the spectral fits and for obtaining accurate spectral parameters. Furthermore, we show that this method provides a powerful tool to study coronal evolution. The rich archives of XMM-Newton, Suzaku, and NuSTAR provide the opportunity to extend this investigation to include several other bright AGN, which will reveal whether the behaviour that we found is common or unique to Mrk 335.

  12. TORUS2015: The AGN unification scheme after 30 years

    NASA Astrophysics Data System (ADS)

    Gandhi, P.; Hoenig, S. F.

    2015-09-01

    The torus paradigm has proved to be remarkably successful at unifying the observed zoo of active galaxy (AGN) classes, despite having many manifest holes. The field is still data-driven with novel observational results at multiple wavelengths emerging rapidly. We are only now beginning to map out the structure of dusty gas feeding and obscuring AGN, and to model its evolution in galaxy growth. But these have also brought out several apparently contradictory results which must hold the key to future progress. As we celebrate 30 years of the paradigm, this is the perfect time to draw together our current knowledge and reassess the state of the field. This will be an international workshop at the University of Southampton, UK, with the objective of laying out the major challenges to the field and paving future research directions. Our hope is to facilitate plenty of informal discussions between multiwavelength observers and theorists, addressing some key issues: * What is the main driver in the unification scheme? What are the roles of orientation, mass accretion rate and feedback? * What is the nature and structure of gas and dust in the torus? Do we have a self-consistent picture across multiple wavelengths? * How critical is the role of the torus as an interface between small nuclear scales and large galactic scales? Does galaxy evolution necessarily require tori? * How close are we to self-consistently simulating nuclear activity including AGN feeding and nuclear star-formation? Workshop Rationale The three themes of accretion, orientation, and evolution will be covered through invited and solicited contributions. Different to other conferences, we are building each session around some key papers that have shaped the field or those with great future potential to do so. We specifically pit competing ideas against each other to help painting a realistic picture of the state-of-the-art. Each session will end with discussion rounds delving into important future

  13. The host galaxies of ultra hard X-ray selected AGN

    NASA Astrophysics Data System (ADS)

    Koss, Michael J.

    One of the great mysteries surrounding active galactic nuclei (AGN) is their triggering mechanism. Since the discovery that almost all massive galaxies host nuclear supermassive black holes, it has become clear that a trigger mechanism is required to 'turn on' and continue to fuel the central black hole. While it is established that accretion processes are responsible for the energy emitted, the source of the accreting material is still controversial. Furthermore, the energy input from phases of black hole growth is thought to be a key regulator in the formation of galaxies and the establishment of various scaling relations. Theorists often invoke galaxy mergers as the violent mechanism to drive gas into the central regions and ignite luminous quasars, but among more common moderate luminosity AGN, there has been great controversy whether secular processes or mergers dominate AGN fueling. A survey in the ultra hard X-ray band (14--195 keV) is an important new way to answer the fundamental question of AGN fueling. This method is independent of selection effects such as dust extinction and obscuration that plague surveys at other wavelengths because of the ability of the primary continuum to easily pass through large columns of obscuring gas and dust (<10 24 cm-2). In this PhD, we have assembled the largest sample of ultra hard X-ray selected AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift BAT sample. We find that these AGN show much higher rates of both mergers and massive spirals suggesting both mergers and accretion of cold gas in late type systems are important in AGN fueling. We also find that the most common AGN survey technique, optical line diagnostics, is heavily biased against finding AGN in mergers or spirals. Finally, in agreement with the merger driven AGN link, we find that dual AGN systems may be more common than current observation suggest since some of them are only detected using high

  14. The host galaxies and narrow-line regions of four double-peaked [OIII] AGNs

    SciTech Connect

    Villforth, Carolin; Hamann, Fred

    2015-03-01

    Major gas-rich mergers of galaxies are expected to play an important role in triggering and fueling luminous active galactic nuclei (AGNs). The mechanism of AGN fueling during mergers, however, remains poorly understood. We present deep multi-band (u/r/z) imaging and long-slit spectroscopy of four double-peaked [OIII] emitting AGNs. This class of object is likely associated with either kiloparsec-separated binary AGNs or final stage major mergers, although AGNs with complex narrow-line regions (NLRs) are known contaminants. Such objects are of interest since they represent the onset of AGN activity during the merger process. Three of the four double-peaked [OIII] emitters studied have been confirmed as major mergers using near-infrared imaging and one is a confirmed X-ray binary AGN. All AGNs are luminous, radio-quiet to radio-intermediate, and have redshifts of 0.1AGN suggests that the merger of a binary black hole can take longer than 1 Gyr. All AGNs hosted by merging galaxies have companions at distances ⩽150 kpc. The NLRs have large sizes (10 kpc < r < 100 kpc) and consist of compact clumps with considerable relative velocities between components (∼200–650 km s{sup −1}). We detect broad, predominantly blue, wings with velocities up to ∼1500 km s{sup −1} in [OIII], indicative of powerful outflows. The outflows are compact (<5 kpc) and co-spatial with nuclear regions showing considerable reddening, consistent with enhanced star formation. One source shows an offset between gas and stellar kinematics, consistent with either a bipolar flow or a counter-rotating gas disk. In all other sources, the ionized gas

  15. VizieR Online Data Catalog: RM AGNs accretion rates and BH masses (Du+, 2016)

    NASA Astrophysics Data System (ADS)

    Du, P.; Wang, J.-M.; Hu, C.; Ho, L. C.; Li, Y.-R.; Bai, J.-M.

    2016-05-01

    We select all AGNs with reverberation mapping (RM) data (here only broad Hβ line), which yield robust BH mass estimates needed for our analysis. All RM AGNs before 2013 are summarized by Bentz et al. (2013ApJ...767..149B). Our project to search for super-Eddington accreting massive black holes (SEAMBHs) has monitored about 25 candidates and successfully measured Hβ lags ({tau}Hβ) in 14 AGNs to date (Du et al. 2015, J/ApJ/806/22) and other five objects monitored between 2014 and 2015 (to be submitted). See section 2 for further explanations. (2 data files).

  16. Fraction Sense: Foundational Understandings.

    PubMed

    Fennell, Francis Skip; Karp, Karen

    2016-08-09

    The intent of this commentary is to identify elements of fraction sense and note how the research studies provided in this special issue, in related but somewhat different ways, validate the importance of such understandings. Proficiency with fractions serves as a prerequisite for student success in higher level mathematics, as well as serving as a gateway to many occupations and varied contexts beyond the mathematics classroom. Fraction sense is developed through instructional opportunities involving fraction equivalence and magnitude, comparing and ordering fractions, using fraction benchmarks, and computational estimation. Such foundations are then extended to operations involving fractions and decimals and applications involving proportional reasoning. These components of fraction sense are all addressed in the studies provided in this issue, with particular consideration devoted to the significant importance of the use of the number line as a central representational tool for conceptually understanding fraction magnitude.

  17. TEMPERED FRACTIONAL CALCULUS

    PubMed Central

    MEERSCHAERT, MARK M.; SABZIKAR, FARZAD; CHEN, JINGHUA

    2014-01-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series. PMID:26085690

  18. Preselecting AGN candidates from multi-wavelength data by ADTree

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxia; Zheng, Hongwen; Zhao, Yongheng

    2005-03-01

    With the information era in astronomy coming, this "data avalanche" may provide many answers to important problems in contemporary astrophysics. The most important problem is sifting through massive amounts of data to mine knowledge. In this paper, we positionally cross-identify multi-wavelength data from optical, near-infrared, and x-ray bands, and then employ alternating decision trees (adtree) to quickly and robustly separate AGN candidates to a high degree of accuracy. We emphasise the application of the method due to the development of large survey projects and the establishment of the virtual observatory, and conclude that the application of data mining algorithms in astronomy is of great importance to discover new knowledge impossible to obtain before, and promote the development of astronomy.

  19. Relativistic Effects on Reflection X-ray Spectra of AGN

    SciTech Connect

    Lee, Khee-Gan; Fuerst, Steven V.; Brandwardi-Raymond, Graziella; Wu, Kinwah; Crowley, Oliver; /University Coll. London

    2007-01-05

    We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and smearing. The degree of distortion depends on the system parameters, and the dependence is stronger for some parameters such as the inner radius of the accretion disk and the disk viewing inclination angles. The relativistic effects are significant and are observable. Improper treatment of the reflection component of the X-ray continuum in spectral fittings will give rise to spurious line-like features, which will mimic the fluorescent emission lines and mask the relativistic signatures of the lines.

  20. Cloudy Skies over AGN: Observations with Simbol-X

    NASA Astrophysics Data System (ADS)

    Salvati, M.; Risaliti, G.

    2009-05-01

    Recent time-resolved spectroscopic X-ray studies of bright obscured AGN show that column density variability on time scales of hours/days may be common, at least for sources with NH>1023 cm-2. This opens new oppurtunities in the analysis of the structure of the circumnuclear medium and of the X-ray source: resolving the variations due to single clouds covering/uncovering the X-ray source provides tight constraints on the source size, the clouds' size and distance, and their average number, density and column density. We show how Simbol-X will provide a breakthrough in this field, thanks to its broad band coverage, allowing (a) to precisely disentangle the continuum and NH variations, and (2) to extend the NH variability analysis to column densities >1023 cm-2.

  1. Synergy Between Observations of AGN with GLAST and MAXI

    SciTech Connect

    Madejski, Grzegorz

    2002-03-25

    In five years' time we will witness the launch of two important missions developed to observe celestial sources in the high energy regime: GLAST, sensitive in the high energy {gamma}-ray band, and MAXI, the all-sky X-ray monitor. Simultaneous monitoring observations by the two instruments will be particularly valuable for variable sources, allowing cross-correlations of time series between the two bands. We present the anticipated results from such observations of active galaxies, and in particular, of the jet-dominated sub-class of AGN known as blazars. We discuss the constraints on the structure and emission processes--and in particular, on the internal shock models currently invoked to explain the particle acceleration processes in blazars--that can be derived with simultaneous {gamma}-ray and X-ray data.

  2. Comparing Narrow- and Broad-line AGNs in a New Diagnostic Diagram for Emission-line Galaxies Based on WISE Data

    NASA Astrophysics Data System (ADS)

    Coziol, R.; Torres-Papaqui, J. P.; Andernach, H.

    2015-06-01

    Using a new color-color diagnostic diagram in the mid-infrared (MIR) built from WISE data, the MIRDD, we compare narrow-emission-line galaxies (NELGs) that exhibit different activity types (star-forming galaxies (SFGs) and active galactic nuclei (AGNs), i.e., LINERs, Seyfert 2 galaxies (Sy2s), and Transition-type Objects (TOs)), as determined using one standard diagnostic diagram in the optical (BPT-VO), with broad-line AGNs (QSOs and Sy1s) and BL Lac objects at low redshift (z≤slant 0.25). We show that the BL Lac objects occupy the same region as the LINERs in the MIRDD, whereas the QSOs and Sy1s occupy an intermediate region between the LINERs and the Sy2s. In the MIRDD these galaxies trace a sequence that can be reproduced by a power law, {{F}ν }={{ν }α }, where the spectral index, α, varies from 0 to -2, which is similar to what is observed in the optical/ultraviolet part of the spectra of AGNs with different luminosities. For the NELGs with different activity types, we perform a stellar-population synthesis analysis, confirming that their specific positions in the MIRD depend on their star formation histories (SFH) and demonstrating that the W2-W3 color is tightly correlated with the level of star formation in their host galaxies. In good agreement with the SFH analysis, a comparison of their MIR colors with the colors yielded by spectral energy distributions (SEDs) of galaxies with different activity types shows that the SED of the LINERs is similar to the SEDs of the QSOs and Sy1s, consistent with AGN galaxies with mild star formation, whereas the SEDs of the Sy2s and TOs are consistent with AGN galaxies with strong star formation components. For the BL Lac objects, we show that their blue MIR colors can only be fitted with an SED that has no star formation component, consistent with AGNs in elliptical-type galaxies. From their similarities in MIR colors and SEDs, we infer that, in the nearby universe, the level of star formation activity most probably

  3. Coordinated UV and X-ray Observations of AGN Outflows

    NASA Astrophysics Data System (ADS)

    Kriss, Gerard A.

    2017-01-01

    Observations of AGN outflows have progressed from the era of single-object surveys to intensive monitoring campaigns spanning weeks to months. The combination of multiple observations, improved temporal coverage, multi-wavelength monitoring in both the X-ray and UV bands, and the baseline of prior historical observations has enabled determinations of the locations, mass flux, and kinetic luminosities of the outflowing absorbing gas in several AGN. Typically the mass flux and kinetic energy are dominated by the higher-ionization X-ray absorbing gas. But the higher-resolution UV observations give a kinematically resolved picture of the overall outflow. In most cases, the outflowing gas is located at parsec to kpc scales, with insufficient kinetic luminosity to have an evolutionary impact on the host galaxy. Multiple coordinated observations have also revealed a new class of UV and X-ray absorbers. They typically show transient, heavy X-ray obscuration in the low-energy spectrum characterized by high column densities of mildly ionized gas. These X-ray obscuration events are accompanied by the appearance of broad, fast, blue-shifted UV absorption lines of moderate ionization, comparable to the X-ray absorbing gas. In the best-studied case of NGC 5548, the strength of the broad UV absorption lines varies with the degree of soft X-ray obscuration first revealed by XMM-Newton spectra. The high outflow velocities, variability timescales of a day or less in the X-ray, and the broad widths suggest an origin in a wind from the accretion disk. This low-ionization component may represent the shielding gas necessary to facilitate disk winds driven by radiative acceleration in UV absorption lines.

  4. The host galaxies of AGN with powerful relativistic jets

    NASA Astrophysics Data System (ADS)

    Olguín-Iglesias, A.; León-Tavares, J.; Kotilainen, J. K.; Chavushyan, V.; Tornikoski, M.; Valtaoja, E.; Añorve, C.; Valdés, J.; Carrasco, L.

    2016-08-01

    We present deep Near-infrared (NIR) images of a sample of 19 intermediate-redshift (0.3AGN) with powerful relativistic jets (L1.4GHz >10^27 WHz^-1), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities L1.4GHz = 10^23.7 - 10^28.3WHz^-1, allowing us to divide our sample into high-excitation (quasar-mode; HERGs) and low-excitation (radio-mode; LERGs) radio galaxies. The host galaxies of our sample are bright and seem to follow the Kormendy relation. Nuclear emission (dominated by non-thermal mechanisms) and host-galaxy magnitudes show a slightly negative weak trend for LERGs. On the other hand, the m_bulge -m_nuc relation is statistically significant for HERGs. Although it may be affected by selection effects, this correlation suggests a close coupling between the relativistic jets and their host galaxy. Our findings are consistent with the excitation state (LERG/HERG) scenario. In this view, LERGs emit the bulk of their energy in the form of radio jets, producing a strong feedback mechanism, and HERGs are affected by galaxy mergers and interactions, which provide a common supply of cold gas to feed both nuclear activity and star formation episodes.

  5. Do the Kepler AGN light curves need reprocessing?

    NASA Astrophysics Data System (ADS)

    Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.; Williams, Joshua; Carini, Michael T.

    2015-10-01

    We gauge the impact of spacecraft-induced effects on the inferred variability properties of the light curve of the Seyfert 1 AGN Zw 229-15 observed by Kepler. We compare the light curve of Zw 229-15 obtained from the Kepler MAST data base with a reprocessed light curve constructed from raw pixel data. We use the first-order structure function, SF(δt), to fit both light curves to the damped power-law PSD (power spectral density) of Kasliwal et al. On short time-scales, we find a steeper log PSD slope (γ = 2.90 to within 10 per cent) for the reprocessed light curve as compared to the light curve found on MAST (γ = 2.65 to within 10 per cent) - both inconsistent with a damped random walk (DRW) which requires γ = 2. The log PSD slope inferred for the reprocessed light curve is consistent with previous results that study the same reprocessed light curve. The turnover time-scale is almost identical for both light curves (27.1 and 27.5 d for the reprocessed and MAST data base light curves). Based on the obvious visual difference between the two versions of the light curve and on the PSD model fits, we conclude that there remain significant levels of spacecraft-induced effects in the standard pipeline reduction of the Kepler data. Reprocessing the light curves will change the model inferenced from the data but is unlikely to change the overall scientific conclusions reached by Kasliwal et al. - not all AGN light curves are consistent with the DRW.

  6. X-ray long-term variations in the low-luminosity AGN NGC 835 and its circumnuclear emission

    NASA Astrophysics Data System (ADS)

    González-Martín, O.; Hernández-García, L.; Masegosa, J.; Márquez, I.; Rodríguez-Espinosa, J. M.; Acosta-Pulido, J. A.; Alonso-Herrero, A.; Dultzin, D.; Esparza Arredondo, D.

    2016-03-01

    Context. Obscured active galactic nuclei (AGNs) are thought to be very common in the Universe. Observations and surveys have shown that the number of sources increases for near galaxies and at the low-luminosity regime (the so-called LLAGNs). Furthermore, many AGNs show changes in their obscuration properties at X-rays that may suggest a configuration of clouds very close to the accretion disk. However, these variations could also be due to changes in the intrinsic continuum of the source. It is therefore important to study nearby AGN to better understand the locus and distribution of clouds in the neighbourhood of the nucleus. Aims: We aim to study the nuclear obscuration of LLAGN NGC 835 and its extended emission using mid-infrared observations. Methods: We present sub-arcsecond-resolution mid-infrared 11.5 μm imaging of the LLAGN galaxy NGC 835 obtained with the instrument CanariCam in the Gran Telescopio CANARIAS (GTC), archival Spitzer/IRS spectroscopy, and archival Chandra data observed in 2000, 2008, and 2013. Results: The GTC/CanariCam 11.5 μm image reveals faint extended emission out to ~6 arcsec. We obtained a nuclear flux of F(11.5 μm) ~ 18 mJy, whereas the extended emission accounts for 90% of the total flux within the 6 arcsec. This means that the low angular resolution (~4 arcsec) IRS spectrum is dominated by this extended emission and not by the AGN. This is clearly seen in the Spitzer/IRS spectrum, which resembles that of star-forming galaxies. Although the extended soft X-ray emission shows some resemblance with that of the mid-infrared, the knots seen at X-rays are mostly located in the inner side of this mid-infrared emission. The nuclear X-ray spectrum of the source has undergone a spectral change between 2000/2008 and 2013. We argue that this variation is most probably due to changes in the hydrogen column density from ~8 × 1023 cm-2 to ~3 × 1023 cm-2. NGC 835 therefore is one of the few LLAGN, together with NGC 1052, in which changes in

  7. Searching for Short Term Variable Active Galactic Nuclei: A Vital Step Towards Using AGN as Standard Candles

    NASA Astrophysics Data System (ADS)

    Kilts, Kelly; Gorjian, Varoujan; Rutherford, Thomas; Kohrs, Russell; Urbanowski, Vincent; Bellusci, Nina; Horton, Savannah; Jones, Dana; Jones, Kaytlyn; Pawelski, Peter; Tranum, Haley; Zhang, Emily

    2017-01-01

    Current models for accretion disk sizes of active galactic nuclei (AGN) do not match the limited observational data available, so there is an active need from the modeling community for many more accretion disk/dusty torus reverberation mapping campaigns with which to better calibrate models. Since short term variable AGN can be more easily monitored for reverberation mapping than long term variable AGN, they can begin to provide data more quickly. This project looked for short term variable AGN in the Young Stellar Object Variability (YSOVAR) survey conducted using the Spitzer Space Telescope. The YSOVAR survey targeted 12 nearby star forming regions for repeated observations. Potential AGN from the YSOVAR data were first selected by color ([3.6] - [4.5] > 0.4) and then by magnitude (m < 14) based on previous Spitzer surveys of known AGN. Since AGN share some similar color characteristics with young stars, images of each YSOVAR region were viewed to remove potential objects near concentrations of known young stellar objects since these were likely also YSOs. The spectral energy distribution (SED) for each remaining potential AGN was then examined for AGN like characteristics. Several potential short term variable AGN were found.

  8. Merger-driven fueling of active galactic nuclei: Six dual and of AGNs discovered with Chandra and Hubble Space Telescope observations

    DOE PAGES

    Comerford, Julia M.; Pooley, David; Barrows, R. Scott; ...

    2015-06-19

    Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates atmore » $$z\\lt 0.34$$, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation $${\\rm \\Delta }x=2.2$$ kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations $${\\rm \\Delta }x\\lt 10$$ kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O III] λ5007 luminosity, on average. Lastly, this could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.« less

  9. Merger-driven Fueling of Active Galactic Nuclei: Six Dual and Offset AGNs Discovered with Chandra and Hubble Space Telescope Observations

    NASA Astrophysics Data System (ADS)

    Comerford, Julia M.; Pooley, David; Barrows, R. Scott; Greene, Jenny E.; Zakamska, Nadia L.; Madejski, Greg M.; Cooper, Michael C.

    2015-06-01

    Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates at z\\lt 0.34, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation Δ x=2.2 kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations Δ x\\lt 10 kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O iii] λ5007 luminosity, on average. This could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.

  10. Merger-driven fueling of active galactic nuclei: Six dual and of AGNs discovered with Chandra and Hubble Space Telescope observations

    SciTech Connect

    Comerford, Julia M.; Pooley, David; Barrows, R. Scott; Greene, Jenny E.; Zakamska, Nadia L.; Madejski, Greg M.; Cooper, Michael C.

    2015-06-19

    Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates at $z\\lt 0.34$, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation ${\\rm \\Delta }x=2.2$ kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations ${\\rm \\Delta }x\\lt 10$ kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O III] λ5007 luminosity, on average. Lastly, this could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.

  11. Testing different AGN tracers on a local sample of Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Pozzi, F.

    2016-08-01

    I will present our new study on a local sample of Seyfert galaxies selected at 12 micron. This sample, given its plenty of information, both photometric and spectroscopic, is a perfect sample to compare, from a statistical point of view, different AGN selection criteria, and AGN derived intrinsic properties. In detail, I will compare AGN activity derived from SED-fitting technique, X-ray luminosity and AGN activity traced by high excitation IR lines, like [NeV] and [OIV]. Moreover, for one particular obscured X-ray Compton-thick source, thanks also to the availability of ALMA data, I will derive a self-consistent overview of the physics behind the emission in different bands,by taking advantage of the photoionization code CLOUDY.

  12. Downstream Effects of the Levee Overtopping at Wilkes-Barre, Pennsylvania During Tropical Storm Agnes.

    DTIC Science & Technology

    1973-04-01

    Davis, March 1973 36. Evaluation of Drought Effects at Lake Atitlan, Arlen D. Feldman 37. Downstream Effects of the Levee Overtopping at Wilkes-Barre, Pa., During Tropical Storm Agnes, Arlen D. Feldman, April 1973

  13. Characterizing the redshifts and luminosities of WISE selected obscured AGN using SALT optical spectra.

    NASA Astrophysics Data System (ADS)

    Hviding, Raphael E.; Hickox, Ryan C.; Hainline, Kevin N.; Carroll, Christopher M.; DiPompeo, Mike A.; Jones, Mackenzie L.

    2016-08-01

    We present the results of several optical spectroscopic surveys covering over 100 candidate luminous obscured active galactic nuclei (AGN) identified by their mid-infrared emission detected with the Wide-Field Infrared Survey Explorer (WISE). These galaxies were selected based on red WISE colors and galaxy-like optical emission, and were studied using long-slit optical spectroscopy with the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT). Our spectra were analyzed to obtain redshifts and emission line flux ratios for each galaxy. These results verify that WISE is an effective section method for luminous obscured AGN, allow for the characterization of redshifts and luminosities of the WISE color selected obscured AGN population, and could potentially contribute to large statistical studies of obscured AGN distributions in the future.

  14. Prospects for AGN Science using the ART-XC on the SRG Mission

    NASA Technical Reports Server (NTRS)

    Swartz, Douglas A.; Elsner, Ronald F.; Gubarev, Mikhail V.; O'Dell, Stephen L.; Ramsey, Brian D.; Bonamente, Massimiliano

    2012-01-01

    The enhanced hard X-ray sensitivity provided by the Astronomical Roentgen Telescope to the Spectrum Roentgen Gamma mission facilitates the detection of heavily obscured and other hard-spectrum cosmic X-ray sources. The SRG all-sky survey will obtain large, statistically-well-defined samples of active galactic nuclei (AGN) including a significant population of local heavily-obscured AGN. In anticipation of the SRG all-sky survey, we investigate the prospects for refining the bright end of the AGN luminosity function and determination of the local black hole mass function and comparing the spatial distribution of AGN with large-scale structure defined by galaxy clusters and groups. Particular emphasis is placed on studies of the deep survey Ecliptic Pole regions.

  15. Starburst and AGN Indicators in Optically Faint X-ray Sources in the Cosmic Evolution Survey

    NASA Astrophysics Data System (ADS)

    Robins, Derek; Elvis, M.; Civano, F.

    2011-01-01

    A sample of 55 faint, X-ray selected objects were chosen for analysis from the COSMOS survey with high quality Keck DEIMOS data. The average redshift of the sample was 1.36, consistent with the average redshift of type 1 AGN in COSMOS of 1.4. Emission lines, NeV - an indicator of AGN luminosity - and OII - an indicator of star formation rate, were measured for a subset of 34 objects. Line properties for these objects were measured. The combination of the two lines is evidence for significant star formation in these obscured AGN. Differences between OII and NeV redshifts were measured carefully. Significant differences between OII and NeV redshifts were found in 10-14 objects, implying OII outflows. The results are consistent with current models of galaxy evolution that invoke an interplay between AGN activity and star formation.

  16. Disentangling Dominance: Obscured AGN Activity versus Star Formation in BPT-Composites

    NASA Astrophysics Data System (ADS)

    Trouille, Laura

    2011-11-01

    Approximately 20% of SDSS emission-line galaxies (ELG) lie in the BPT-comp regime, between the Kauffmann et al. (2003) empirically determined SF-dominated regime and the Kewley et al. (2001) theoretically predicted AGN-dominated regime. BPT-AGN, on the other hand, make up only 11% of the ELG population. Whether to include the significant number of BPT-comp in samples of AGN or samples of star-forming galaxies is an open question and has important implications for galaxy evolution studies, metallicity studies, etc. Using a large pectroscopic sample of GOODS-N and LH galaxies with deep Chandra imaging, we perform an X-ray stacking analysis of BPT-comp. We find the stacked signal to be X-ray hard. This X-ray hardness can be indicative of obscured AGN activity or the presence of HMXBs associated with ongoing star formation. In order to distinguish between these scenarios, we perform an IR stacking analysis using Spitzer 24 micron data. The stacked BPT-comp lies well above the expected value for L_x/L_IR for pure star-forming galaxies; similarly for the X-ray detected BPT-comp. We also find that the BPT-comp lie in the AGN-dominated regime of our new TBT diagnostic, which uses [NeIII]/[OII] versus rest-frame g-z colour to identify AGN and star forming galaxies out to z=1.4. [NeIII], which has a higher ionisation potential than other commonly used forbidden emission lines, appears to foster a more reliable selection of AGN-dominated galaxies. These findings suggest that both the X-ray and optical signal in BPT-comp are dominated by obscured or low accretion rate AGN activity rather than star formation. This is in contrast to claims by previous optical emission-line studies that the signal in BPT-comp is dominated by star-formation activity. Therefore, we recommend that groups carefully consider the impact of excluding or including BPT-comp on the interpretation of their results. For example, for studies involving determining the bolometric contribution from AGN activity

  17. Mechanism of hypertriglyceridemia in human apolipoprotein (apo) CIII transgenic mice. Diminished very low density lipoprotein fractional catabolic rate associated with increased apo CIII and reduced apo E on the particles.

    PubMed Central

    Aalto-Setälä, K; Fisher, E A; Chen, X; Chajek-Shaul, T; Hayek, T; Zechner, R; Walsh, A; Ramakrishnan, R; Ginsberg, H N; Breslow, J L

    1992-01-01

    Hypertriglyceridemia is common in the general population, but its mechanism is largely unknown. In previous work human apo CIII transgenic (HuCIIITg) mice were found to have elevated triglyceride levels. In this report, the mechanism for the hypertriglyceridemia was studied. Two different HuCIIITg mouse lines were used: a low expressor line with serum triglycerides of approximately 280 mg/dl, and a high expressor line with serum triglycerides of approximately 1,000 mg/dl. Elevated triglycerides were mainly in VLDL. VLDL particles were 1.5 times more triglyceride-rich in high expressor mice than in controls. The total amount of apo CIII (human and mouse) per VLDL particle was 2 and 2.5 times the normal amount in low and high expressors, respectively. Mouse apo E was decreased by 35 and 77% in low and high expressor mice, respectively. Under electron microscopy, VLDL particles from low and high expressor mice were found to have a larger mean diameter, 55.2 +/- 16.6 and 58.2 +/- 17.8 nm, respectively, compared with 51.0 +/- 13.4 nm from control mice. In in vivo studies, radiolabeled VLDL fractional catabolic rate (FCR) was reduced in low and high expressor mice to 2.58 and 0.77 pools/h, respectively, compared with 7.67 pools/h in controls, with no significant differences in the VLDL production rates. In an attempt to explain the reduced VLDL FCR in transgenic mice, tissue lipoprotein lipase (LPL) activity was determined in control and high expressor mice and no differences were observed. Also, VLDLs obtained from control and high expressor mice were found to be equally good substrates for purified LPL. Thus excess apo CIII in HuCIIITg mice does not cause reduced VLDL FCR by suppressing the amount of extractable LPL in tissues or making HuCIIITg VLDL a bad substrate for LPL. Tissue uptake of VLDL was studied in hepatoma cell cultures, and VLDL from transgenic mice was found to be taken up much more slowly than control VLDL (P < 0.0001), indicating that HuCIIITg VLDL is

  18. How accurate is [CII] tracing star formation in nearby luminous AGN?

    NASA Astrophysics Data System (ADS)

    Husemann, Bernd

    We propose [CII] line mapping with FIFI-LS to complete observations for 4 nearby luminous AGN as part of our Close AGN Reference Survey (CARS) unobserved in Cycle 4. Our aim is to create a spatially-resolved multi-wavelength dataset to understand whether and how AGN can control star formation in their hosts. We already obtained wide-field optical IFU spectroscopy with MUSE to disentangle emission from HII regions and photoionized gas by the AGN across the galaxies. Currently, there is a high pressure to understand the impact of AGN especially at the peak of cosmic star formation beyond z>2 where measuring the SF is diffcult. The [CII] line at 158microns has become an important diagnostic for SF in high-redshift galaxies with the advent of ALMA. However, the line can be excited by various mechanisms in a multi-phase ISM. In particular the hard radiation field of AGN is a major concern which can only be quantified in nearby galaxies. FIFI-LS aboard SOFIA is currently the only way to perform follow-up observations of FIR emission lines. By uniquily combining MUSE and FIFI-LS we will be able to 1. test if the empirical [CII]-SFR scaling relation hold for luminous nearby AGN, 2. quantifiy any deviation as a function of AGN luminosity, 3. test if the [CII] line kinematics are strongly affected by outflows or trace solely the kinematics of the cold gas disc. Those observations for nearby galaxies with FIFI-LS are crucially needed to establish a reference frame for interpreting high-redshift observation with ALMA at similar physical resolution.

  19. How accurate is [CII] tracing star formation in nearby luminous AGN?

    NASA Astrophysics Data System (ADS)

    Husemann, Bernd

    2015-10-01

    We propose [CII] line mapping with FIFI-LS for a sample of 8 nearby luminous AGN as part of our Close AGN Reference Survey (CARS). Our aim is to create a spatially-resolved multi-wavelength dataset to understand whether and how AGN can control star formation in their hosts. We already obtained wide-field optical IFU spectroscopy with MUSE to disentangle emission from HII regions and photoionized gas by the AGN across the galaxies. Currently, there is a high pressure to understand the impact of AGN especially at the peak of cosmic star formation beyond z>2 where measuring the SF is diffcult. The [CII] line at 158microns has become an important diagnostic for SF in high-redshift galaxies with the advent of ALMA. However, the line can be excited by various mechanisms in a multi-phase ISM. In particular the hard radiation field of AGN is a major concern which can only be quantified in nearby galaxies. FIFI-LS aboard SOFIA is currently the only way to perform follow-up observations of FIR emission lines. By uniquily combining MUSE and FIFI-LS we will be able to 1. test if the empirical [CII]-SFR scaling relation hold for luminous nearby AGN, 2. quantifiy any deviation as a function of AGN luminosity, 3. test if the [CII] line kinematics are strongly affected by outflows or trace solely the kinematics of the cold gas disc. Those observations for nearby galaxies with FIFI-LS are crucially needed to establish a reference frame for interpreting high-redshift observation with ALMA at similar physical resolution.

  20. Results from the NuSTAR Survey of Swift/BAT AGN

    NASA Astrophysics Data System (ADS)

    Balokovic, Mislav; Harrison, Fiona

    2015-08-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) has enabled studies of the local active galactic nuclei (AGN) to extend into the spectral window above 10 keV with unprecedented spatial resolution and two orders of magnitude better sensitivity than any other instrument operating in that energy range. As a part of its long-term extragalactic program NuSTAR is surveying the nearby population of AGN detected at hard X-ray energies by the Swift Burst Alert Telescope (Swift/BAT). We present results based on 15-25 ks observations of ~150 Swift/BAT AGN surveyed in the first 2.5 years of NuSTAR operation. This sample forms an atlas of the highest quality hard X-ray spectra available to date for a large number of AGN. Assuming a range of hard X-ray spectral models, phenomenological as well as physically motivated, we constrain the main spectral parameters for each source individually and test the applicability of the models on a large sample for the first time. This analysis allows us to determine distributions of the main spectral parameters (spectral index, high-energy cut-off, absorption column, reflection strength, iron line equivalent width) in a well-defined population of nearby AGN. We find that approximately 70% of obscured AGN spectra can be well modeled in terms of simple models used in the literature, while the rest requires careful consideration of more advanced models. We will discuss the implications for the local AGN population, the effects on interpretation of high-redshift AGN observations, and the limitations of the current results.

  1. Ultra-fast outflows (aka UFOs) in AGNs and their relevance for feedback

    NASA Astrophysics Data System (ADS)

    Cappi, Massimo; Tombesi, F.; Giustini, M.; Dadina, M.; Braito, V.; Kaastra, J.; Reeves, J.; Chartas, G.; Gaspari, M.; Vignali, C.; Gofford, J.; Lanzuisi, G.

    2012-09-01

    During the last decade, several observational evidences have been accumulated for the existence of massive, high velocity winds/outflows (aka UFOs) in nearby AGNs and, possibly, distant quasars. I will review here such evidences, present some of the latest results in this field, and discuss the relevance of UFOs for both understanding the physics of accretion/ejection flows on supermassive black holes, and for quantifying the amount of AGN feedback.

  2. The Search for Molecular Outflows in Local Volume AGNs with Herschel-PACS

    NASA Astrophysics Data System (ADS)

    Stone, M.; Veilleux, S.; Meléndez, M.; Sturm, E.; Graciá-Carpio, J.; González-Alfonso, E.

    2016-08-01

    We present the results from a systematic search for galactic-scale, molecular (OH 119 μm) outflows in a sample of 52 Local Volume (d\\lt 50 Mpc) Burst Alert Telescope detected active galactic nuclei (BAT AGNs) with Herschel-PACS. We combine the results from our analysis of the BAT AGNs with the published Herschel/PACS data of 43 nearby (z\\lt 0.3) galaxy mergers, mostly ultra-luminous infrared galaxies (ULIRGs) and QSOs. The objects in our sample of BAT AGNs have, on average, ˜ 10{--}100 times lower AGN luminosities, star formation rates, and stellar masses than those of the ULIRG and QSO samples. OH 119 μm is detected in 42 of our BAT AGN targets. Evidence for molecular outflows (i.e., OH absorption profiles with median velocities more blueshifted than -50 km s-1 and/or blueshifted wings with 84% velocities less than -300 km s-1) is seen in only four BAT AGNs (NGC 7479 is the most convincing case). Evidence for molecular inflows (i.e., OH absorption profiles with median velocities more redshifted than 50 km s-1) is seen in seven objects, although an inverted P-Cygni profile is detected unambiguously in only one object (Circinus). Our data show that both the starburst and AGN contribute to driving OH outflows, but the fastest OH winds require AGNs with quasar-like luminosities. We also confirm that the total absorption strength of OH 119 μm is a good proxy for dust optical depth as it correlates strongly with the 9.7 μm silicate absorption feature, a measure of obscuration originating in both the nuclear torus and host galaxy disk. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  3. Angular Broadening of Intraday Variable AGNs II. Interstellar and Intergalactic Scattering

    DTIC Science & Technology

    2008-01-01

    scattering from any possible intergalactic contribution, we have searched for pulsars within 1 of theAGNs in our sample.We find no pulsars this close to any...of our sources.Given the relatively low density of pulsars on the sky, a significantly larger sample of AGNs would be required in order to make such a...in pulsar dynamic spectra (Hill et al. 2005). We can also use the difference between the scintillating and nonscintillating sources to set

  4. Differences in Halo-scale Environments between Type 1 and Type 2 AGNs at Low Redshift

    NASA Astrophysics Data System (ADS)

    Jiang, Ning; Wang, Huiyuan; Mo, Houjun; Dong, Xiao-Bo; Wang, Tinggui; Zhou, Hongyan

    2016-12-01

    Using low-redshift (z\\lt 0.09) samples of active galactic nuclei (AGNs), normal galaxies and groups of galaxies selected from the Sloan Digital Sky Survey, we study the environments of Type 1 and Type 2 AGNs, both on small and large scales. Comparisons are made for galaxy samples matched in redshift, r-band luminosity, [O iii] luminosity, and also the position in groups (central or satellite). We find that Type 2 AGNs and normal galaxies reside in similar environments. Type 1 and Type 2 AGNs have similar clustering properties on large scales (≳ 1 {h}-1 {Mpc}), but at scales smaller than 100 {h}-1 {kpc}, Type 2s have significantly more neighbors than Type 1s (3.09 ± 0.69 times more for central AGNs at ≲ 30 {h}-1 {kpc}). These results suggest that Type 1 and Type 2 AGNs are hosted by halos of similar masses, as can also be seen directly from the mass distributions of their host groups (˜ {10}12 {h}-1 {M}⊙ for centrals and ˜ {10}13 {h}-1 {M}⊙ for satellites). Type 2s have significantly more satellites around them, and the distribution of their satellites is also more centrally concentrated. The host galaxies of both types of AGNs have similar optical properties, but their infrared colors are significantly different. Our results suggest that the simple unified model based solely on torus orientation is not sufficient, but that galaxy interactions in dark matter halos must have played an important role in the formation of the dust structure, which obscures AGNs.

  5. The Wide-angle Outflow of the Lensed z = 1.51 AGN HS 0810+2554

    NASA Astrophysics Data System (ADS)

    Chartas, G.; Cappi, M.; Hamann, F.; Eracleous, M.; Strickland, S.; Giustini, M.; Misawa, T.

    2016-06-01

    We present results from X-ray observations of the gravitationally lensed z = 1.51 active galactic nucleus (AGN) HS 0810+2554 performed with the Chandra X-ray Observatory and XMM-Newton. Blueshifted absorption lines are detected in both observations at rest-frame energies ranging between ˜1 and 12 keV at ≳99% confidence. The inferred velocities of the outflowing components range between ˜0.1c and ˜0.4c. A strong emission line at ˜6.8 keV that is accompanied by a significant absorption line at ˜7.8 keV is also detected in the Chandra observation. The presence of these lines is a characteristic feature of a P-Cygni profile supporting the presence of an expanding, outflowing, highly ionized iron absorber in this quasar. Modeling of the P-Cygni profile constrains the covering factor of the wind to be ≳0.6, assuming disk shielding. A disk-reflection component is detected in the XMM-Newton observation accompanied by blueshifted absorption lines. The XMM-Newton observation constrains the inclination angle to be <45° at 90% confidence, assuming that the hard excess is due to blurred reflection from the accretion disk. The detection of an ultrafast and wide-angle wind in an AGN with intrinsic narrow absorption lines (NALs) would suggest that quasar winds may couple efficiently with the intergalactic medium and provide significant feedback if ubiquitous in all NAL and broad absorption line (BAL) quasars. We estimate the mass-outflow rate of the absorbers to lie in the range of 1.5-3.4 M ⊙ yr-1 for the two observations. We find that the fraction of kinetic to electromagnetic luminosity released by HS 0810+2554 is large (ɛ k = 9{}-6+8), which suggests that magnetic driving is likely a significant contributor to the acceleration of this outflow.

  6. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

    Describes a very successful attempt to