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Register a new userUnshifted Metastable He I* Mini-Broad Absorption Line System in the Narrow Line Type 1 Quasar SDSS J080248.18$+$551328.9
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We report the identification of an unusual absorption line system in the quasar SDSS J080248.18$+$551328.9 and present a detailed study of the system, incorporating follow-up optical and NIR spectroscopy. A few tens of absorption lines are detected, including He I*, Fe II* and Ni II* that arise from metastable or excited levels, as well as resonant lines in Mg I, Mg II, Fe II, Mn II, and Ca II. All of the isolated absorption lines show the same profile of width $Delta vsim 1,500$km s$^{-1}$ centered at a common redshift as that of the quasar emission lines, such as [O II], [S II], and hydrogen Paschen and Balmer series. With narrow Balmer lines, strong optical Fe II multiplets, and weak [O III] doublets, its emission line spectrum is typical for that of a narrow-line Seyfert 1 galaxy (NLS1). We have derived reliable measurements of the gas-phase column densities of the absorbing ions/levels. Photoionization modeling indicates that the absorber has a density of $n_{rm H} sim (1.0-2.5)times 10^5~ {rm cm}^{-3}$ and a column density of $N_{rm H} sim (1.0-3.2)times 10^{21} sim {rm cm}^{-2}$, and is located at $Rsim100-250$ pc from the central super-massive black hole. The location of the absorber, the symmetric profile of the absorption lines, and the coincidence of the absorption and emission line centroid jointly suggest that the absorption gas is originated from the host galaxy and is plausibly accelerated by stellar processes, such as stellar winds zhy{and/or} supernova explosions. The implications for the detection of such a peculiar absorption line system in an NLS1 are discussed in the context of co-evolution between super-massive black hole growth and host galaxy build-up.
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The accretion of interstellar medium onto the central super massive black holes is widely accepted as the source of the gigantic energy released by the active galactic nuclei. But few pieces of observational evidence have been confirmed directly demonstrating the existence of the inflows. The absorption line system in the spectra of quasar SDSS J112526.12+002901.3 presents an interesting example, in which the rarely detected hydrogen Balmer and metastable He I absorption lines are found redshifted to the quasars rest frame along with the low-ionization metal absorption lines Mg II, Fe II, etc. The repeated SDSS spectroscopic observations suggest a transverse velocity smaller than the radial velocity. The motion of the absorbing medium is thus dominated by infall. The He I* lines present a powerful probe to the strength of ionizing flux, while the Balmer lines imply a dense environment. With the help of photoionization simulations, we find the absorbing medium is exposed to the radiation with ionization parameter $Uapprox 10^{-1.8}$, and the density is $n(mathrm{H})approx 10^9 mathrm{cm}^{-3}$. Thus the absorbing medium is located $sim 4 mathrm{pc}$ away from the central engine. According to the similarity in the distance and physical conditions between the absorbing medium and the torus, we strongly propose the absorption line system as a candidate for the accretion inflow which originates from the inner surface of the torus.
CRTS J084133.15+200525.8 is an optically bright quasar at z=2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V~17.3 between 2002 and 2008. Then, over the following five years, the source slowly brightened by approximately one magnitude, to V~16.2. Only ~1 in 10,000 quasars show such extreme variability, as quantified by the extreme parameters derived for this quasar assuming a damped random walk model. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line (FeLoBAL) quasar with extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. We report the first definitive redshift for this source, based on the detection of broad H-alpha in a Keck/MOSFIRE spectrum. Absorption systems separated by several 1000 km/s in velocity show coordinated weakening in the depths of their troughs as the continuum flux increases. We interpret the broad absorption line variability to be due to changes in photoionization, rather than due to motion of material along our line of sight. This source highlights one sort of rare transition object that astronomy will now be finding through dedicated time-domain surveys.
The properties of narrow-line Seyfert 1 (NLS1) galaxies, the links and correlations between them, and the physics behind them, are still not well understood. Apart from accretion rates and black hole masses, density and outflows were speculated to be among the main drivers of the NLS1 phenomenon. Here, we utilize the diagnostic power of the [SII]6716,6731 intensity ratio to measure the density of the NLR systematically and homogeneously for a large sample of NLS1 galaxies, and we perform a comparison with a sample of broad-line type 1 AGN. We report the discovery of a zone of avoidance in density in the sense that AGN with broad lines (FWHM_Hbeta > 2000 km/s) avoid low densities, while NLS1 galaxies show a wider distribution in the NLR density, including a significant number of objects with low densities. A correlation analysis further shows that the Eddington ratio L/L_Edd anti-correlates with density. We investigate a number of different models for the zone of avoidance in density. Supersolar metallicities and temperature effects, a strong starburst contribution in NLS1 galaxies, different NLR extents and selective obscuration are considered unlikely. Possible differences in the fraction of matter-bounded clouds and differences in the interstellar media of the host galaxies of NLS1 galaxies and broad-line Seyfert 1 (BLS1) galaxies can only be tested further with future observations. We tentatively favor the effects of winds/outflows, stronger in NLS1 galaxies than in BLS1 galaxies, to explain the observations.
We consider whether Broad Absorption Line Quasars (BAL QSOs) and Narrow Line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt & Gallagher (2000) and Boroson (2002). For this purpose we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/Ledd, although BAL QSOs have slightly lower L/Ledd. BAL QSOs and NLS1s in general have high FeII/H$beta$ and low [OIII]/H$beta$ ratios following the classic Boroson & Green eigenvector 1 relation. We also found that the mass accretion rates $dot{M}$ of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 msun/year. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M-$sigma$ plot, we find that BAL QSOs contain fully developed black holes. Applying a principal component analysis to our sample we find eigenvector 1 to correspond to the Eddington ratio L/Ledd, and eigenvector 2 to black hole mass.
I report the discovery of blueshifted broad absorption line (BAL) troughs in at least six transitions of the Balmer series of hydrogen (Hbeta to H9) and in CaII, MgII and excited FeII in the quasar SDSS J125942.80+121312.6. This is only the fourth active galactic nucleus known to exhibit Balmer absorption, all four in conjunction with low-ionization BAL systems containing excited Fe II. The substantial population in the n=2 shell of H I in this quasars absorber likely arises from Ly-alpha trapping. In an absorber sufficiently optically thick to show Balmer absorption, soft X-rays from the quasar penetrate to large tau_Lyalpha and ionize H I. Recombination then creates Ly-alpha photons that increase the n=2 population by a factor tau_Lyalpha since they require about tau_Lyalpha scatterings to diffuse out of the absorber. Observing Ly-alpha trapping in a quasar absorber requires a large but Compton-thin column of gas along our line of sight which includes substantial H I but not too much dust. Presumably the rarity of Balmer-line BAL troughs reflects the rarity of such conditions in quasar absorbers.
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