Radio Loud AGN in the Context of the Eigenvector 1 Parameter Space

We consider the properties of radio-loud (RL) AGN in the context of the Eigenvector 1 (E1) parameter space. RL sources show a restricted E1 parameter space occupation relative to the radio-quiet (RQ) majority. The Fanaroff-Riley II ``parent population'' of relatively un-boosted RL sources (median radio/optical flux ratio ~490) shows the most restricted occupation. RL sources have different broad line properties (and inferred black hole masses and Eddington ratios). FWHM H_beta for the broad line component in RL sources are at least twice as large as the RQ majority. The average broad FeII emission line strength is also about half that for RQ sources. Our sample suggests that the RL cutoff occurs near R_k=70 or logP(6cm)=32.0 ergs/s/Hz. Sources below this cutoff are RQ although we cannot rule out the existence of a distinct intermediate population. We show that the Doppler boosted core-dominated RL sources (median flux ratio ~1000) lie towards smaller FWHM(H_beta_bc) and stronger FeII in E1 as expected if the lines arise in an accretion disk. Our subsample of superluminal sources, with orientation inferred from the synchrotron self Compton model, reinforce this general E1 trend and allow us to estimate the role of source orientation in driving E1 domain occupation.Comment: 9 pages, 3 figures, accepted for publication in ApJ

Probing the Ionizing Continuum of Narrow-Line Seyfert 1 Galaxies. I.Observational Results

We present optical spectra and emission-line ratios of 12 Narrow-Line Seyfert 1 (NLS1) galaxies that we observed to study the ionizing EUV continuum. A common feature in the EUV continuum of active galactic nuclei is the big blue bump (BBB), generally associated with thermal accretion disk emission. While Galactic absorption prevents direct access to the EUV range, it can be mapped by measuring the strength of a variety of forbidden optical emission lines that respond to different EUV continuum regions. We find that narrow emission-line ratios involving [OII]3727, Hbeta, [OIII]5007, [OI]6300, Halpha,[NII]6583, and [SII]6716,6731 indicate no significant difference between NLS1s and Broad-Line Seyfert 1 (BLS1) galaxies, which suggests that the spectral energy distributions of their ionizing EUV - soft X-ray continua are similar. The relative strength of important forbidden high ionization lines like [NeV]3426 compared to HeII4686 and the relative strength of [FeX]6374 appear to show the same range as in BLS1 galaxies. However, a trend of weaker F([OI]6300)/F(Halpha) emission-line ratios is indicated for NLS1s compared to BLS1s. To recover the broad emission-line profiles we used Gaussian components. This approach indicates that the broad Hbeta profile can be well described with a broad component (FWHM = 3275 +- 800 km/s) and an intermediate broad component (FWHM = 1200 +- 300 km/s). The width of the broad component is in the typical range of normal BLS1s. The emission-line flux that is associated with the broad component in these NLS1s amounts to at least 60% of the total flux. Thus it dominates the total line flux, similar to BLS1 galaxies.Comment: 34 pages, 9 figures. accepted for publication in the Astrophys.Journa

Hazards of volcanic lakes: analysis of Lakes Quilotoa and Cuicocha, Ecuador

International audienceVolcanic lakes within calderas should be viewed as high-risk systems, and an intensive lake monitoring must be carried out to evaluate the hazard of potential limnic or phreatic-magmatic eruptions. In Ecuador, two caldera lakes ? Lakes Quilotoa and Cuicocha, located in the high Andean region >3000 a.s.l. ? have been the focus of these investigations. Both volcanoes are geologically young or historically active, and have formed large and deep calderas with lakes of 2 to 3 km in diameter, and 248 and 148 m in depth, respectively. In both lakes, visible gas emissions of CO2 occur, and an accumulation of CO2 in the deep water body must be taken into account. Investigations were carried out to evaluate the hazards of these volcanic lakes, and in Lake Cuicocha intensive monitoring was carried out for the evaluation of possible renewed volcanic activities. At Lake Quilotoa, a limnic eruption and diffuse CO2 degassing at the lake surface are to be expected, while at Lake Cuicocha, an increased risk of a phreatic-magmatic eruption exists

Tidal Disruption of a Star By a Black Hole : Observational Signature

We have modeled the time-variable profiles of the Halpha emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a million solar mass black hole. Two tidal disruption event simulations were carried out using a three dimensional relativistic smooth-particle hydrodynamic code, to describe the early evolution of the debris during the first fifty to ninety days. We have calculated the physical conditions and radiative processes in the debris using the photoionization code CLOUDY. We model the emission line profiles in the period immediately after the accretion rate onto the black hole became significant. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. As a result of the uneven distribution of the debris and the existence of a ``tidal tail'' (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Moreover, the predicted line profiles vary on fairly short time scales (of order hours to days). Given the accretion rate onto the black hole we also model the Halpha light curve from the debris and the evolution of the Halpha line profiles in time.Comment: 20 pages, 9 figures, to appear in ApJ, 1 August 2004 issue; mpeg simulations of tidal disruption available at http://www.astro.psu.edu/users/tamarab/tdmovies.htm

X-ray Absorption and Optical Extinction in the Partially Obscured Seyfert Nucleus in Mrk 1393

We present a detailed study of the X-ray and optical spectra of the luminous Seyfert galaxy Mrk 1393, which revealed variable partial obscuration of the active nucleus. The X-ray spectra obtained by XMM-Newton and Swift show moderate absorption with a column density around 3x10^21 cm^-2, consistent with a dust-reddening interpretation of the steep Balmer decrement seen in recent optical spectra. The X-ray flux in the 0.5 to 2 keV band during the XMM-Newton observation in 2005 and Swift observation in 2006 was a factor 6 brighter than that of the ROSAT All Sky Survey in 1991. In the past 4 years, the broad H\alpha line brightened by a factor of 4 accompanied by a decrease in the Balmer decrement. A comparison with literature spectra reveals variations in the dust extinction on time scales of several years, suggesting that the obscuring material is very close to the active nucleus. These observations indicate that a dust-to-gas ratio as high as the Galactic value can be present in moderately thick gas in the vicinity of the central engine within a few parsecs. We suggest that the obscuring material may be debris disrupted from the dusty torus.Comment: 25 pages, 5 figures, accepted to A

X-ray Observations of the Seyfert galaxy LB 1727 (1H 0419-577)

We discuss the properties of the Seyfert 1.5 galaxy LB 1727, also known as 1H 0419-577, from X-ray observations obtained by ASCA and ROSAT along with optical observations from earlier epochs. ASCA shows only modest (< 20%) variations in X-ray flux within or between the observations. In contrast, a daily monitoring campaign over 1996 Jun - Sept by the ROSAT HRI instrument reveals the soft X-ray (0.1-2 keV) flux to have increased by a factor ~3. The 2 - 10 keV continuum can be parameterized as a power-law with a photon index Gamma ~ 1.45-1.68 across ~0.7 - 11 keV in the rest-frame. We also report the first detection of iron Kalpha line emission in this source. Simultaneous ASCA and ROSAT data show the X-ray spectrum to steepen sharply at a rest-energy \~0.75 keV, the spectrum below this energy can be parameterized as a power-law of slope Gamma ~3.6. We show that LB 1727 is one of the few Seyferts for which we can rule out the possibility that the presence of a warm absorber is solely responsible for the spectral steepening in the soft X-ray regime. Consideration of the overall spectral-energy-distribution for this source indicates the presence of a pronounced XUV-bump visible in optical, ultraviolet and soft X-ray data.Comment: 27 pages, 7 figures. LaTeX with encapsulated postscript. To appear in the Astrophysical Journa

Enhanced Star Formation in Narrow Line Seyfert 1 AGN revealed by Spitzer

We present new low resolution Spitzer mid-infrared spectroscopy of a sample of 20 ROSAT selected local Narrow Line Seyfert 1 galaxies (NLS1s). We detect strong AGN continuum in all and clear PAH emission in 70% of the sources. The 6.2 micron PAH luminosity spans three orders of magnitudes, from ~10^(39) erg/s to ~10^(42) erg/s providing strong evidence for intense ongoing star formation in the circumnuclear regions of these sources. Using the IRS/Spitzer archive we gather a large number of additional NLS1s and their broad line counterparts (BLS1s) and constructed NLS1 and BLS1 sub-samples to compare them in various ways. The comparison shows a clear separation according to FWHM(H_beta) such that objects with narrower broad H_beta lines are the strongest PAH emitters. We test this division in various ways trying to remove biases due to luminosity and aperture size. Specifically, we find that star formation activity around NLS1 AGN is larger than around BLS1 of the same AGN luminosity. The above result seems to hold over the entire range of distance and luminosity. Moreover the star formation rate is higher in low black hole mass and high L/L_Edd systems indicating that black hole growth and star formation are occurring simultaneously.Comment: 30 pages, 11 figures, 4 tables. Now accepted in MNRA

Understanding AGN-Host Connection in Partially Obscured Active Galactic Nuclei. Part I: The Nature of AGN+HII Composites

The goal of our serial papers is to examine the evolutionary connection between AGN and star formation in its host galaxy in the partially obscured AGNs (i.e., Seyfert 1.8 and 1.9 galaxies). Taking advantage of these galaxies, the properties of both components can be studied together by direct measurements. In this paper, we focus on the broad-line composite galaxies (composite AGNs) which are located between the theoretical and empirical separation lines in the [NII]/Ha vs. [OIII]/Hb diagram. These galaxies are searched for from the composite galaxies provided by the SDSS DR4 MPA/JHU catalogs. After re-analyze the spectra, we perform a fine classification for the 85 composite AGNs in terms of the BPT diagrams. All the objects located below the three theoretical separation lines are associated with a young stellar population (<1Gyrs), while either a young or old stellar population is identified in the individual multiply-classified object. The multiply-classified objects with a very old stellar population are located in the LINER region in the [OI]/Ha vs. [OIII]/Hb diagram. We then consider the connection between AGN and star formation to derive the key results. The Eddington ratio inferred from the broad Ha emission, the age of the stellar population of AGN's host as assessed by D_n(4000), and the line ratio [OI]/Ha are found to be related with each other. These relations strongly support the evolutionary scenario in which AGNs evolve from high L/L_Edd state with soft spectrum to low L/L_Edd state with hard spectrum as young stellar population ages and fades. The significant correlation between the line ratio [OI]/Ha and D_n(4000) leads us to suggest that the line ratio could be used to trace the age of stellar population in type I AGNs.Comment: 39 pages, 11 figures, 1 table, accepted by Ap