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Register a new userA Tentative Size-Luminosity Relation for the Iron Emission-Line Region in Quasars
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New reverberation mapping measurements of the size of the optical iron emission-line region in quasars are provided, and a tentative size-luminosity relation for this component is reported. Combined with lag measurements in low-luminosity sources, the results imply an emission-region size that is comparable to and at most twice that of the H$beta$ line, and is characterized by a similar luminosity dependence. This suggests that the physics underlying the formation of the optical iron blends in quasars may be similar to that of other broad emission lines.
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This paper reports results of the third-year campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs) in active galactic nuclei (AGNs) between 2014-2015. Ten new targets were selected from quasar sample of Sloan Digital Sky Survey (SDSS), which are generally more luminous than the SEAMBH candidates in last two years. H$beta$ lags ($tau_{_{rm Hbeta}}$) in five of the 10 quasars have been successfully measured in this monitoring season. We find that the lags are generally shorter, by large factors, than those of objects with same optical luminosity, in light of the well-known $R_{_{rm Hbeta}}-L_{5100}$ relation. The five quasars have dimensionless accretion rates of $dot{mathscr{M}}=10-10^3$. Combining measurements of the previous SEAMBHs, we find that the reduction of H$beta$ lags tightly depends on accretion rates, $tau_{_{rm Hbeta}}/tau_{_{R-L}}proptodot{mathscr{M}}^{-0.42}$, where $tau_{_{R-L}}$ is the H$beta$ lag from the normal $R_{_{rm Hbeta}}-L_{5100}$ relation. Fitting 63 mapped AGNs, we present a new scaling relation for the broad-line region: $R_{_{rm Hbeta}}=alpha_1ell_{44}^{beta_1},minleft[1,left(dot{mathscr{M}}/dot{mathscr{M}}_cright)^{-gamma_1}right]$, where $ell_{44}=L_{5100}/10^{44},rm erg~s^{-1}$ is 5100 AA continuum luminosity, and coefficients of $alpha_1=(29.6_{-2.8}^{+2.7})$ lt-d, $beta_1=0.56_{-0.03}^{+0.03}$, $gamma_1=0.52_{-0.16}^{+0.33}$ and $dot{mathscr{M}}_c=11.19_{-6.22}^{+2.29}$. This relation is applicable to AGNs over a wide range of accretion rates, from $10^{-3}$ to $10^3$. Implications of this new relation are briefly discussed.
I report a tentative ($sim4sigma$) emission line at $ u=100.84,$GHz from COS-3mm-1, a 3mm-selected galaxy reported by Williams et al. 2019 that is undetected at optical and near infrared wavelengths. The line was found in the ALMA Science Archive after re-processing ALMA band 3 observations targeting a different source. Assuming the line corresponds to the $rm CO(6to5)$ transition, this tentative detection implies a spectroscopic redshift of $z=5.857$, in agreement with the galaxys redshift constraints from multi-wavelength photometry. This would make this object the highest redshift 3mm-selected galaxy and one of the highest redshift dusty star-forming galaxies known to-date. Here, I report the characteristics of this tentative detection and the physical properties that can be inferred assuming the line is real. Finally, I advocate for follow-up observations to corroborate this identification and to confirm the high-redshift nature of this optically-dark dusty star-forming galaxy.
A method is proposed for measuring the size of the broad emission line region (BLR) in quasars using broadband photometric data. A feasibility study, based on numerical simulations, points to the advantages and pitfalls associated with this approach. The method is applied to a subset of the Palomar-Green quasar sample for which independent BLR size measurements are available. An agreement is found between the results of the photometric method and the spectroscopic reverberation mapping technique. Implications for the measurement of BLR sizes and black hole masses for numerous quasars in the era of large surveys are discussed.
We investigate the variability behaviour of the broad Hb emission-line to driving continuum variations in the best-studied AGN NGC 5548. For a particular choice of BLR geometry, Hb surface emissivity based on photoionization models, and using a scaled version of the 13 yr optical continuum light curve as a proxy for the driving ionizing continuum, we explore several key factors that determine the broad emission line luminosity L, characteristic size R(RW), and variability amplitude (i.e., responsivity) eta, as well as the interplay between them. For fixed boundary models which extend as far as the hot-dust the predicted delays for Hb are on average too long. However, the predicted variability amplitude of Hb provides a remarkably good match to observations except during low continuum states. We suggest that the continuum flux variations which drive the redistribution in Hb surface emissivity F(r) do not on their own lead to large enough changes in R(RW) or eta(eff). We thus investigate dust-bounded BLRs for which the location of the effective outer boundary is modulated by the continuum level and the dust-sublimation and dust-condensation timescales. We find that in order to match the observed variability amplitude of broad Hb in NGC 5548 a rather static outer boundary is preferred. Intriguingly, we show that the most effective way of reducing the Hb delay, while preserving its responsivity and equivalent width, is to invoke a smaller value in the incident ionizing photon flux Phi(H) for a given ionizing source--cloud radial distance r, than is normally inferred from the observed UV continuum flux and typical models of the continuum SED.
We aim to study the structure and kinematics of the broad line region (BLR) of a sample of 27 gravitationally lensed quasars with up to five different epochs of observation. This sample is composed of ~100 spectra from the literature plus 22 unpublished spectra of 11 systems. We measure the magnitude differences in the broad emission line (BEL) wings and statistically model the distribution of microlensing magnifications to determine a maximum likelihood estimate for the sizes of the C IV, C III], and Mg II emitting regions. The BELs in lensed quasars are expected to be magnified differently owing to the different sizes of the regions from which they originate. Focusing on the most common BELs in our spectra (C IV, C III], and Mg II), we find that the low-ionization line Mg II is only weakly affected by microlensing. In contrast, the high-ionization line C IV shows strong microlensing in some cases, indicating that its emission region is more compact. Thus, the BEL profiles are deformed differently depending on the geometry and kinematics of the corresponding emitting region. We detect microlensing in either the blue or the red wing (or in both wings with different amplitudes) of C IV in more than 50% of the systems and find outstanding asymmetries in the wings of QSO 0957+561, SDSS J1004+4112, SDSS J1206+4332, and SDSS J1339+1310. This observation indicates that the BLR is, in general, not spherically symmetric and supports the existence of two regions in the BLR, one insensitive to microlensing and another that only shows up when it is magnified by microlensing.
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