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Constraining the physical conditions of the ionized media in the vicinity of an active supermassive black hole (SMBH) is crucial to understanding how these complex systems operate. Metal emission lines such as iron (Fe) are useful probes to trace the gaseous media's abundance, activity, and evolution in these accreting systems. Among these, the Feii emission has been the focus of many prior studies to investigate the energetics, kinematics, and composition of the broad-emission line region (BELR) from where these emission lines are produced. In this paper, we present the first simultaneous Feii modeling in the optical and near-infrared (NIR) regions. We use cloudy photoionization code to simulate both spectral regions in the wavelength interval 4000–12,000 Å. We compare our model predictions with the observed line flux ratios for I Zw (Zwicky) 1—a prototypical strong Feii-emitting active galactic nuclei (AGNs). This allows setting constraints on the BLR cloud density and metal content that is optimal for the production of the Feii emission, which can be extended to I Zw 1-like sources by examining a broad parameter space. We demonstrate the salient and distinct features of the Feii pseudo-continuum in the optical and NIR, giving special attention to the effect of micro-turbulence on the intensity of the Feii emission. [ABSTRACT FROM AUTHOR]

Using bona-fide black hole (BH) mass estimates from reverberation mapping and the line ratio [Si  vi ] 1.963 |$\rm{\mu m}$| /Brγbroad as tracer of the AGN ionizing continuum, a novel BH-mass scaling relation of the form log(M BH) = (6.40 ± 0.17) − (1.99 ± 0.37) × log ([Si  vi ]/Brγbroad), dispersion 0.47 dex, over the BH mass interval, 106–108 M⊙ is found. Following on the geometrically thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe one of main drivers of the relation is the effective temperature of the disc, which is effectively sampled by the [Si  vi ] 1.963 |$\rm{\mu m}$| coronal line for the range of BH masses considered. By means of cloudy photoionization models, the observed anticorrelation appears to be formally in line with the thin disc prediction T disc ∝  M BH−1/4. [ABSTRACT FROM AUTHOR]

We study a sample of 67 active galactic nuclei (AGN) with moderate to strong Feii emission to investigate the relation between the observed AGN continuum and the lines produced by the broad line region (BLR), in particular, Feii. We found that the continuum in the optical/near‐infrared can be described in terms of two components: a power‐law, characterized by the spectral index α, and hot dust emission, represented by a Plank function of temperature T. These two parameters seem not to be related to the strength of Feii emission. In addition to Feii, we study other low‐ionization BLR lines such as Oi and Caii (hereafter CaT). We found that the full‐width at half maximum of these three lines are similar, suggesting that they are produced in the same spatial region of the BLR. We measure the Feii strength in the optical and the near‐infrared region and found that they are strongly correlated. This result evidences the presence of a common excitation mechanism for the Feii emission in the wavelength interval 4000–24000 Å. [ABSTRACT FROM AUTHOR]

In this second paper in the series, we carefully analyze the observational properties of the optical Fe ii and near-IR Ca ii triplet in active galactic nuclei (AGNs), as well as the luminosity, black hole mass, and Eddington ratio in order to define the driving mechanism behind the properties of our sample. The Ca ii shows an inverse Baldwin effect, bringing out the particular behavior of this ion with respect to the other low-ionization lines such as H β. We performed a principal component analysis, where 81.2% of the variance can be explained by the first three principal components drawn from the FWHMs, luminosity, and equivalent widths. The first principal component (PC1) is primarily driven by the combination of black hole mass and luminosity with a significance over 99.9%, which in turn is reflected in the strong correlation of the PC1 with the Eddington ratio. The observational correlations are better represented by the Eddington ratio; thus, it could be the primary mechanism behind the strong correlations observed in the Ca ii –Fe ii sample. Since calcium belongs to the α-elements, the Fe ii /Ca ii flux ratio can be used as a chemical clock for determining the metal content in AGNs and trace the evolution of the host galaxies. We confirm the de-enhancement of the ratio Fe ii /Ca ii by the Eddington ratio, suggesting a metal enrichment of the BLR in intermediate-z with respect to low-z objects. A larger sample, particularly at z > 2, is needed to confirm the present results. [ABSTRACT FROM AUTHOR]

Characterizing high-z quasar environments is key to understanding the coevolution of quasars and the surrounding galaxies. To restrict their global picture, we statistically examine the g-dropout galaxy overdensity distribution around 570 faint quasar candidates at z ∼ 4, based on the Hyper Suprime-Cam Subaru Strategic Program survey. We compare the overdensity significances of g-dropout galaxies around the quasars with those around g-dropout galaxies, and find no significant difference between their distributions. A total of 4 (22) out of the 570 faint quasars, , are found to be associated with the >4σ overdense regions within an angular separation of 1.8 (3.0) arcmin, which is the typical size of protoclusters at this epoch. This is similar to the fraction of g-dropout galaxies associated with the >4σ overdense regions. This result is consistent with our previous work in which and of luminous quasars detected in the Sloan Digital Sky Survey exist in the >4σ overdense regions within 1.′8 and 3.′0 separations, respectively. Therefore, we suggest that the galaxy number densities around quasars are independent of their luminosity, and most quasars do not preferentially appear in the richest protocluster regions at z ∼ 4. The lack of an apparent positive correlation between the quasars and the protoclusters implies that (i) the gas-rich major merger rate is relatively low in the protocluster regions, (ii) most high-z quasars may appear through secular processes, or (iii) some dust-obscured quasars exist in the protocluster regions. [ABSTRACT FROM AUTHOR]

We report the rest-frame ultraviolet luminosity function of g-dropout galaxies in 177 protocluster candidates (PC UVLF) at z ∼ 4 selected in the Hyper Suprime-Cam Subaru Strategic Program. Comparing it with the UVLF of field galaxies at the same redshift, we find that the PC UVLF shows a significant excess toward the bright end. This excess cannot be explained by the contribution of only active galactic nuclei, and we also find that this excess is more significant in higher density regions. Assuming that all protocluster members are located on the star formation main sequence, the PC UVLF can be converted into a stellar mass function. Consequently, our protocluster members are inferred to have a 2.8 times more massive characteristic stellar mass than that of the field Lyman break galaxies at the same redshift. This study, for the first time, clearly shows that the enhancement in star formation or stellar mass in overdense regions can generally be seen as early as at z ∼ 4. We also estimate the star formation rate density (SFRD) in protocluster regions as ≃6%–20% of the cosmic SFRD, based on the measured PC UVLF after correction for the selection incompleteness in our protocluster sample. This high value suggests that protoclusters make a nonnegligible contribution to the cosmic SFRD at z ∼ 4, as previously suggested by simulations. Our results suggest that protoclusters are essential components for galaxy evolution at z ∼ 4. [ABSTRACT FROM AUTHOR]

We present near-infrared spectroscopy of the NLS1 galaxy PHL 1092 (z  = 0.394), the strongest Fe  ii emitter ever reported, combined with optical and UV data. We modelled the continuum and the broad emission lines using a power-law plus a blackbody function and Lorentzian functions, respectively. The strength of the Fe  ii emission was estimated using the latest Fe  ii templates in the literature. We re-estimate the ratio between the Fe  ii complex centred at 4570 Å and the broad component of H β, R 4570, obtaining a value of 2.58, nearly half of that previously reported (R 4570 = 6.2), but still placing PHL 1092 among extreme Fe  ii emitters. The full width at half-maximum (FWHM) values found for low-ionization lines are very similar (FWHM ∼ 1200 km s−1), but significantly narrower than those of the hydrogen lines (FWHMH β ∼ 1900 km s−1). Our results suggest that the Fe  ii emission in PHL 1092 follows the same trend as in normal Fe  ii emitters, with Fe  ii being formed in the outer portion of the BLR and co-spatial with Ca  ii , and O  i , while H β is formed closer to the central source. The flux ratio between the UV lines suggests high densities, log(n H) ∼ 13.0 cm−3, and a low ionization parameter, log(U) ∼ −3.5. The flux excess found in the Fe  ii bump at 9200 Å after the subtraction of the NIR Fe  ii template and its comparison with optical Fe  ii emission suggests that the above physical conditions optimize the efficiency of the Ly α-fluorescence process, which was found to be the main excitation mechanism in the Fe  ii production. We discuss the role of PHL 1092 in the eigenvector 1 context. [ABSTRACT FROM AUTHOR]

In this work, we study the optical properties of 58 CSS/GPS radio sources selected from the literature in order to determine the impact of the radio-jet in the circumnuclear environment of these objects. We obtained optical spectra for all sources from SDSS-DR12 and performed a stellar population synthesis using the Starlight code. Our results indicate that the sample is dominated by intermediate to old stellar populations and there is no strong correlation between optical and radio properties of these sources. [ABSTRACT FROM AUTHOR]