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Title: Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442

Abstract

We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He i lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. They were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, i.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would bemore » very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.« less

Authors:
; ; ; ; ; ;  [1];  [2]; ;  [3]
  1. Polar Research Institute of China, Jinqiao Road 451, Shanghai 200136 (China)
  2. Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan 650011 (China)
  3. Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China)
Publication Date:
OSTI Identifier:
22654445
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 843; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ACCRETION DISKS; BALMER LINES; HYDROGEN; OSCILLATOR STRENGTHS; OSCILLATORS; PHOTOIONIZATION; QUASARS; RESOLUTION; SPECTRA; TELESCOPES; VELOCITY; WAVELENGTHS

Citation Formats

Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA725E.
Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, & Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442. United States. doi:10.3847/2041-8213/AA725E.
Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Sat . "Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442". United States. doi:10.3847/2041-8213/AA725E.
@article{osti_22654445,
title = {Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442},
author = {Shi, Xi-Heng and Pan, Xiang and Zhang, Shao-Hua and Sun, Lu-Ming and Ji, Tuo and Liu, Bo and Zhou, Hong-Yan and Wang, Jian-Guo and Yang, Chen-Wei and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn},
abstractNote = {We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He i lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. They were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, i.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would be very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.},
doi = {10.3847/2041-8213/AA725E},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 843,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}
  • IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasar are within the range normally measured in quasars. Its redshift is low enough to allow the morphology of the host galaxy to be studied in deep broad-band and intermediate-band CCD images. The galaxy appears to be a large spiral with a very long arm or tail. Themore » inclination angle is 57 deg, which rules out the possibility that the line of sight to the nucleus intersects a large path length in a galactic disk. 32 references.« less
  • We explore the formation of the hydrogen La, Balmer, and Paschen lines and the Balmer continuum in highly idealized QSO broad emission line clouds (ELCs) of constant temperature and density irradiated by an external source of power-law spectral form. We simultaneously solve the equations governing excitation, ionization, and transfer of both external and diffuse radiation fields. Our calculations show that the typical observed broad emission line radios of La/Ha, Hb/Ha, Pa/Ha, and Balmer continuum/Ha can be understood for ELC conditions in the temperature range 7 x 10/sup 3/< or approx. =T/sub e/< or approx. =2 x 10/sup 4/ K, hydeogenmore » density range 10/sup 8/< or approx. =n/sub H/< or approx. =10/sup 12/ cm/sup -3/, and for external fluxes F< or approx. =/sup -6/ ergs cm/sup -2/ s/sup -1/ at the Lyman continuum limit.« less
  • We present IUE and optical observations demonstrating that the z/sub em/ = 0.29 ZSO PG 1700+518 is a broad absorption line (BAL) QSO. This object is unique because of its low redshift and because it is one of only two BAL QSOs which exhibit moderate strength Mg II BALs. The discovery is noteworthy because, barring systematics between redshift and the strength of Mg II BALs in BAL QSOs, it suggests that the fraction of QSOs with BALs at low redshifts is comparable to the observed fraction at high redshifts. We discuss implications for the evolutionary history of the QSO andmore » its BAL region (BALR). Optical spectroscopy of PG 1700+518 shows substantial Fe II emission, but little (if any) broad (O III) lambda 5007 emission. The lack of broad (O III) emission requires either BALR covering factors of q/sub c/<0.05 or electron densities of n/sub e/>10/sup 5/-10/sup 6/ m/sup -3/ for larger values of q/sub c/. The model we present for PG 1700+518 has a BALR-central source distance of r = 31(n/sub e//10/sup 6/)/sup -1/2/ pc. For the highest luminosity BAL QSOs, this distance scales to 10 or more times larger. We discuss why models with n/sub e/>10/sup 6/-10/sup 7/ cm/sup -3/ are favored.« less
  • We present deep Keck/LRIS spectroscopy and Hubble Space Telescope/WFC3 imaging in the rest-frame optical for a sample of eight galaxies at z {approx} 1.5 with high photometrically determined stellar masses. The data are combined with five Very Large Telescope/X-Shooter spectra. We find that these 13 galaxies have high velocity dispersions, with a median of {sigma} = 301 km s{sup -1}. This high value is consistent with their relatively high stellar masses and compact sizes. We study their stellar populations using the strength of Balmer absorption lines, which are not sensitive to dust absorption. We find a large range in Balmermore » absorption strength, with many galaxies showing very strong lines indicating young ages. The median H{delta}{sub A} equivalent width, determined directly or inferred from the H10 line, is 5.4 A, indicating a luminosity-weighted age of {approx}1 Gyr. Although this value may be biased toward higher values because of selection effects, high-dispersion galaxies with such young ages are extremely rare in the local universe. Interestingly, we do not find a simple correlation with rest-frame U - V color: some of the reddest galaxies have very strong Balmer absorption lines, which may indicate the importance of multiple bursts of star formation. These results demonstrate that many high-dispersion galaxies at z {approx} 1.5 were recently quenched. This implies that there must be a population of star-forming progenitors at z {approx} 2 with high velocity dispersions or linewidths, which are notoriously absent from CO/H{alpha} selected surveys.« less