scholarly journals Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 94
Author(s):  
Paola Marziani ◽  
Ascension del Olmo ◽  
Jaime Perea ◽  
Mauro D’Onofrio ◽  
Swayamtrupta Panda
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
General Purpose ◽  
Emission Lines ◽  
Impact Excitation ◽  
Ionization Degree ◽  
Uv Emission ◽  
Spectral Diagnostics ◽  
Ionization Parameter

This paper reviews several basic emission properties of the UV emission lines observed in the spectra of quasars and type-1 active galactic nuclei, mainly as a function of the ionization parameter, metallicity, and density of the emitting gas. The analysis exploits a general-purpose 4D array of the photoionization simulations computed using the code CLOUDY, covering ionization parameter in the range 10−4.5–10+1.0, hydrogen density nH∼107–1014 cm−3, metallicity Z between 0.01 and 100 Z⊙, and column density in the range 1021–1023 cm−2. The focus is on the most prominent UV emission lines observed in quasar spectra, namely Nvλ1240, Siivλ1397, Oiv]λ1402, Civλ1549, Heiiλ1640, Aliiiλ1860, Siiii]λ1892, and Ciii]λ1909, and on the physical conditions under which electron-ion impact excitation is predicted to be the dominant line producer. Photoionization simulations help constrain the physical interpretation and the domain of applicability of spectral diagnostics derived from measurements of emission line ratios, reputed to be important for estimating the ionization degree, density, and metallicity of the broad line emitting gas, as well as the relative intensity ratios of the doublet or multiplet components relevant for empirical spectral modeling.

scholarly journals Quasars as standard candles II

2019 ◽  
Vol 631 ◽  
pp. A120 ◽  
Author(s):  
F. Salvestrini ◽  
G. Risaliti ◽  
S. Bisogni ◽  
E. Lusso ◽  
C. Vignali
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
Galactic Nuclei ◽  
Observational Cosmology ◽  
X Ray ◽  
Uv Emission ◽  
Wide Range ◽  
Photon Index ◽  
Lower Redshift

A tight non-linear relation between the X-ray and the optical-ultraviolet (UV) emission has been observed in active galactic nuclei (AGN) over a wide range of redshift and several orders of magnitude in luminosity, suggesting the existence of an ubiquitous physical mechanism regulating the energy transfer between the accretion disc and the X-ray emitting corona. Recently, our group developed a method to use this relation in observational cosmology, turning quasars into standardizable candles. This work mainly seeks to investigate the potential evolution of this correction at high redshifts. We thus studied the LX − LUV relation for a sample of quasars in the redshift range 4 <  z <  7, adopting the selection criteria proposed in our previous work regarding their spectral properties. The resulting sample consists of 53 type 1 (unobscured) quasars, observed either with Chandra or XMM-Newton, for which we performed a full spectral analysis, determining the rest-frame 2 keV flux density, as well as more general X-ray properties such as the estimate of photon index, and the soft (0.5–2 keV) and hard (2–10 keV) unabsorbed luminosities. We find that the relation shows no evidence for evolution with redshift. The intrinsic dispersion of the LX–LUV for a sample free of systematics/contaminants is of the order of 0.22 dex, which is consistent with previous estimates from our group on quasars at lower redshift.

scholarly journals THE PREVALENCE OF NARROW OPTICAL Fe II EMISSION LINES IN TYPE 1 ACTIVE GALACTIC NUCLEI

2010 ◽  
Vol 721 (2) ◽  
pp. L143-L147 ◽  
Author(s):  
Xiao-Bo Dong ◽  
Luis C. Ho ◽  
Jian-Guo Wang ◽  
Ting-Gui Wang ◽  
Huiyuan Wang ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines

scholarly journals First HETDEX Spectroscopic Determinations of Lyα and UV Luminosity Functions at z = 2–3: Bridging a Gap between Faint AGNs and Bright Galaxies

2021 ◽  
Vol 922 (2) ◽  
pp. 167
Author(s):  
Yechi Zhang ◽  
Masami Ouchi ◽  
Karl Gebhardt ◽  
Erin Mentuch Cooper ◽  
Chenxu Liu ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Bright Galaxy ◽  
Number Density ◽  
Luminosity Functions ◽  
Best Fit

Abstract We present Lyα and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0–3.5 determined by the untargeted optical spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg2 of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Lyα emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s−1) Lyα emission lines. We derive the Lyα (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in log L Ly α / [ erg s − 1 ] = 43.3 – 45.5 (−27 < M UV < −20) by the 1/V max estimator. Our results reveal that the bright-end hump of the Lyα LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be α Sch = − 1.70 − 0.14 + 0.13 , which indicates that α Sch steepens from z = 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Lyα-emitting objects (X LAE) increases from M UV * ∼ − 21 to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X Lyα decreases from faint magnitudes to M UV * , suggesting a valley in the X Lyα –magnitude relation at M UV * . Comparing our UV LF of type 1 AGNs at z = 2–3 with those at z = 0, we find that the number density of faint (M UV > −21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright (M UV < −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.

scholarly journals The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

2014 ◽  
Vol 54 (7) ◽  
pp. 1382-1388 ◽  
Author(s):  
G. La Mura ◽  
M. Berton ◽  
S. Ciroi ◽  
V. Cracco ◽  
F. Di Mille ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Emission Lines ◽  
X Ray

scholarly journals Wolf-Rayet stars in Active Galactic Nuclei

1999 ◽  
Vol 193 ◽  
pp. 760-761
Author(s):  
Robin J.R. Williams ◽  
John E. Dyson ◽  
Judith J. Perry
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Emission Lines ◽  
Supply Rate ◽  
Stellar Cluster ◽  
Uv Emission ◽  
Ram Pressure

Starbursts, black holes and AGN have strong observational links, as discussed elsewhere in these proceedings. Perry & Dyson (1985 (PD), see also Perry 1994) studied the role of shocks around supernovae and stellar wind bubbles in the nuclei of active galaxies. Both the ejecta and the ambient ISM are initially shocked to high temperatures. PD found that while the shocked gas is maintained at high pressure by ram pressure, it cools rapidly, to then produce the observed optical and UV emission lines. The mass supply rate from the nuclear starburst, inferred from the strength of the emission lines, tallies well with that required by an accreting black hole to generate the observed luminosity. A symbiosis between a starburst stellar cluster and an accreting black hole naturally generates the observational features associated with QSOs.

scholarly journals Soft X-ray emission lines in the X-ray binary Swift J1858.6–0814 observed with XMM–Newton Reflection Grating Spectrometer: disc atmosphere or wind?

2020 ◽  
Vol 498 (1) ◽  
pp. 68-76 ◽  
Author(s):  
D J K Buisson ◽  
D Altamirano ◽  
M Díaz Trigo ◽  
M Mendez ◽  
M Armas Padilla ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Accretion Disc ◽  
Emission Lines ◽  
X Ray ◽  
Grating Spectrometer ◽  
Optical Wavelengths ◽  
X Ray Binaries ◽  
Ionization Parameter ◽  
Reflection Grating

ABSTRACT We find soft X-ray emission lines from the X-ray binary Swift J1858.6–0814 in data from XMM–NewtonReflection Grating Spectrometer (RGS): N vii, O vii, and O viii, as well as notable residuals short of a detection at Ne ix and other higher ionization transitions. These could be associated with the disc atmosphere, as in accretion disc corona sources, or with a wind, as has been detected in Swift J1858.6–0814 in emission lines at optical wavelengths. Indeed, the N vii line is redshifted, consistent with being the emitting component of a P-Cygni profile. We find that the emitting plasma has an ionization parameter log (ξ) = 1.35 ± 0.2 and a density n &gt; 1.5 × 1011 cm−3. From this, we infer that the emitting plasma must be within 1013 cm of the ionizing source, ∼5 × 107 rg for a 1.4 M⊙ neutron star, and from the line width that it is at least 104 rg away [2 × 109(M/1.4 M⊙) cm]. We compare this with known classes of emission-line regions in other X-ray binaries and active galactic nuclei.

SDSS J154751.94+025550 with double-peaked broad H β but single-peaked broad H α: a candidate for central binary black hole system?

2021 ◽  
Vol 507 (4) ◽  
pp. 5205-5213
Author(s):  
XueGuang Zhang
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Broad Line ◽  
Line Profiles ◽  
Physical Conditions ◽  
Binary Black Hole ◽  
Sinusoidal Function

ABSTRACT In this manuscript, an interesting blue active galactic nuclei (AGNs) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H β but single-peaked broad H α. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical conditions to two central BLRs in a central BBH system in SDSS J1547. Furthermore, the long-term light curve from CSS can be well described by a sinusoidal function with a periodicity about 2159 d, providing further evidence to support the expected central BBH system in SDSS J1547. Therefore, it is interesting to treat different line profiles of broad Balmer emission lines as intrinsic indicators of central BBH systems in broad line AGN. Under assumptions of BBH systems, 0.125 per cent of broad-line AGN can be expected to have very different line profiles of broad Balmer emission lines. Future study on more broad line AGN with very different line profiles of broad Balmer emission lines could provide further clues on the different line profiles of broad Balmer emission lines as indicator of BBH systems.

scholarly journals Constraints on the production and escape of ionizing radiation from the emission-lines of metal-poor star-forming galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 121-122
Author(s):  
A. Plat ◽  
S. Charlot ◽  
G. Bruzual ◽  
A. Feltre ◽  
A. Vidal-Garca ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Radiative Shocks ◽  
Metal Poor Star

AbstractTo understand how the nature of the ionizing sources and the leakage of ionizing photons in high-redshift galaxies can be constrained from their emission-line spectra, we compare emission-line models of star-forming galaxies including leakage of ionizing radiation, active galactic nuclei (AGN) and radiative shocks, with observations of galaxies at various redshifts with properties expected to approach those of primeval galaxies.

scholarly journals A Systematic Search for Dual AGNs in Merging Galaxies (Astro-daring): III: Results from the SDSS Spectroscopic Surveys

2021 ◽  
Vol 162 (6) ◽  
pp. 276
Author(s):  
Yang-Wei Zhang ◽  
Yang Huang ◽  
Jin-Ming Bai ◽  
Xiao-Wei Liu ◽  
Jian-guo Wang ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Angular Separation ◽  
Careful Analysis ◽  
Emission Lines ◽  
Host Galaxies ◽  
Merging Galaxies ◽  
The Third ◽  
First Time ◽  
Consistent Approach

Abstract As the third installment in a series systematically searching dual active galactic nuclei (AGN) among merging galaxies, we present the results of 20 dual AGNs found by using the SDSS fiber spectra. To reduce the flux contamination from both the fiber aperture and seeing effects, the angular separation of two cores in our merging galaxy pairs sample is restricted at least larger than 3″. By careful analysis of the emission lines, 20 dual AGNs are identified from 61 merging galaxies with their two cores both observed by the SDSS spectroscopic surveys. 15 of them are identified for the first time. The identification efficiency is about 32.79% (20/61), comparable to our former results (16 dual AGNs identified from 41 merging galaxies) based on the long-slit spectroscopy. Interestingly, two of the 20 dual AGNs show two prominent cores in radio images and their radio powers show they as the radio-excess AGNs. So far, 31 dual AGNs are found by our project and this is the current largest dual AGN sample, ever constructed with a consistent approach. This sample, together with more candidates from ongoing observations, is of vital importance to study the AGN physics and the coevolution between the supermassive black holes and their host galaxies.

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