AGN black hole mass estimates using polarization in broad emission lines

Savić, Đorđe; Goosmann, R. W.; Popović, L. Č.; Marin, Frédéric; Afanasiev, V. L.

doi:10.1051/0004-6361/201732220

Cited by 50 publications

(77 citation statements)

References 76 publications

(110 reference statements)

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“…Another method is based on polarisation of the broad emission lines (e.g. Afanasiev & Popović 2015;Songsheng & Wang 2018;Savić et al 2018), and has been applied to Ark 120 by Afanasiev & Popović (2015). The inferred a BH mass of 1.04 +1.38 −0.58 × 10 8 M that is compatible within its error bars with the values used in this work.…”

Section: Black Hole Mass Valuesupporting

confidence: 62%

A deep X-ray view of the bare AGN Ark 120

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Reeves

et al. 2019

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Context. The spin of supermassive black holes (SMBH) in active galactic nuclei (AGN) can be determined from spectral signature(s) of relativistic reflection such as the X-ray iron Kα line profile, but this can be rather uncertain when the line of sight intersects the so-called warm absorber and/or other wind components as these distort the continuum shape. Therefore, AGN showing no (or very weak) intrinsic absorption along the line-of-sight such as Ark 120, a so-called bare AGN, are the ideal targets for SMBH spin measurements. However, in our previous work on Ark 120, we found that its 2014 X-ray spectrum is dominated by Comptonisation, while the relativistic reflection emission only originates at tens of gravitational radii from the SMBH. As a result, we could not constrain the SMBH spin from disc reflection alone. Aims. Our aim is to determine the SMBH spin in Ark 120 from an alternative technique based on the global energetics of the disc-corona system. Indeed, the mass accretion rate (Ṁ) through the outer disc can be measured from the optical-UV emission, while the bolometric luminosity (Lbol) can be fairly well constrained from the optical to hard X-rays spectral energy distribution, giving access to the accretion efficiency η = Lbol/(Ṁc2) which depends on the SMBH spin. Methods. The spectral analysis uses simultaneous XMM-Newton (OM and pn) and NuSTAR observations on 2014 March 22 and 2013 February 18. We applied the OPTXCONV model (based on OPTXAGNF) to self consistently reproduce the emission from the inner corona (warm and hot thermal Comptonisation) and the outer disc (colour temperature corrected black body), taking into account both the disc inclination angle and relativistic effects. For self-consistency, we modelled the mild relativistic reflection of the incident Comptonisation components using the XILCONV convolution model. Results. We infer a SMBH spin of 0.83+0.05−0.03, adopting the SMBH reverberation mass of 1.50 × 108 M⊙. In addition, we find that the coronal radius decreases with increasing flux (by about a factor of two), from 85+13−10Rg in 2013 to 14 ± 3 Rg in 2014. Conclusions. This is the first time that such a constraint is obtained for a SMBH spin from this technique, thanks to the bare properties of Ark 120, its well determined SMBH reverberation mass, and the presence of a mild relativistic reflection component in 2014 which allows us to constrain the disc inclination angle. We caution that these results depend on the detailed disc-corona structure, which is not yet fully established. However, the realistic parameter values (e.g. Lbol/LEdd, disc inclination angle) found suggest that this is a promising method to determine spin in moderate-Ṁ AGN.

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Section: Black Hole Mass Valuesupporting

confidence: 62%

A deep X-ray view of the bare AGN Ark 120

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Reeves

et al. 2019

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“…Better constraints might be obtained by considering polarized lines, as discussed in Popovic et al (2018) and Savić et al (2018), for example, because the width of the line directly measures the radial velocity of the material and is thus connected to the position of the emitting material in the BLR. We leave this for a future work.…”

Section: Resultsmentioning

confidence: 99%

Reverberation mapping of AGNs through continuum polarization

Lobos

Goosmann

Hameury

et al. 2020

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Context. The size and geometry of the broad-line region (BLR) in active galactic nuclei (AGNs) are among the main ingredients in determining the mass of the accreting black hole. Size and geometry can be constrained by determining the delay between the optical continuum and the flux reprocessed by the BLR, in particular, through the emission lines. Aims. We propose here that the delay between polarized and unpolarized light can also be used in much the same way to constrain the size of the BLR; we verify that meaningful results can be expected from observations using this technique. Methods. We used our code STOKES to simulate polarized radiative transfer. We determined the response of the environment of the central source (BLR, dust torus, and polar wind) to randomly generated fluctuations in the central source. We then calculated the cross correlation between the simulated polarized flux and the total flux to estimate the time delay that would be provided by observations using the same method. Results. The BLR is the main contributor to the delay between the polarized flux and the total flux. This delay is independent of the observation wavelength. Conclusions. This validates the use of polarized radiation in the optical/UV band to estimate the geometrical properties of the BLR in type I AGNs, in which the viewing angle is close to pole-on and the BLR is not obscured by the dust torus.

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“…The equation above has been tested in a group of broad line AGNs (see Afanasiev and Popović 2015;, where the measurements of SMBH masses with polarization method were compared with other methods (reverberation and M BH − σ method), and it was found that the polarization method gives very good SMBH mass estimates. On the other hand, the limitation of the method was investigated by Savić et al (Savić et al 2018) using the STOKES code, and it was found that the method can be used in the case where, beside Keplerian-like motion, also some outflows/inflows exist in the BLR. The method is robust and can be applied for one epoch observations, and also can be applied for different emission lines.…”

Section: Polarization In Broad Lines -A Methods For Smbh Mass Measuremmentioning

confidence: 99%

“…These facts are often used to estimate the SMBH masses. Additionally, it has been found, recently, that polarization in broad lines of Type 1 AGNs can be used for SMBH mass measurements (see Afanasiev and Popović 2015;Savić et al 2018;Afanasiev et al 2019), and that this method gives good agreement in comparison with reverberation and M SMBHσ * methods (Afanasiev et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Broad spectral lines in AGNs and supermassive black hole mass measurements

Popović

2020

Open Astronomy

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The mass measurement of supermassive black holes (SMBHs) is a very complex task. Between several methods for SMBH mass measurements, some of them use the spectral lines, which indicate the motion of the emitting/absorbing material around an SMBH. Mostly, there is an assumption of virialization of line emitting gas in the region which is close to the central SMBH. In this paper we will give an overview of methods for the SMBH mass measurements using broad emission spectral lines observed in Type 1 AGNs. First we give the basic idea to use the parameters of broad lines to SMBH mass measurements. After that we give an overview of broad lines from X-ray (Fe kα) to the IR (Pashen and Brecket lines) which have been used for SMBH mass estimates. Additionally, we describe and discuss a new method for SMBH mass measurements using the polarization in the broad lines emitted from Type 1 AGNs.

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AGN black hole mass estimates using polarization in broad emission lines

Cited by 50 publications

References 76 publications

A deep X-ray view of the bare AGN Ark 120

A deep X-ray view of the bare AGN Ark 120

Reverberation mapping of AGNs through continuum polarization

Broad spectral lines in AGNs and supermassive black hole mass measurements

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