Virial Mass Research Articles

A candidate for central tidal disruption event in the broad line AGN SDSS J1605 with double-peaked broad H β

ABSTRACT In this letter, motivated by double-peaked broad Balmer emission lines probably related to tidal disruption events (TDEs), a potential TDE candidate is reported in Sloan Digital Sky Survey (SDSS) J160536+134838 (=SDSS J1605) at z ∼ 0.44 having quasar-like spectrum but with double-peaked broad H β. The long-term Catalina Sky Survey (CSS) light curve can be naturally described by a main-sequence star of $2.82_{-0.19}^{+0.20}{\rm M_\odot }$ disrupted by the central black hole (BH) of $144_{-21}^{+26} \times 10^6{\rm M_\odot }$ in SDSS J1605. Meanwhile, the All-Sky Automated Survey for SuperNovae light curves afterwards show none apparent trend variability, indicating the bright CSS flare in SDSS J1605 unique and different enough from variability of normal active galactic nuclei (AGN). Furthermore, there is a consistency between the TDE model determined sizes of debris with the sizes of emission regions for the double-peaked broad H β described by the accretion disc model, supporting the disc-like broad emission line regions (BLRs) probably related to a central TDE in SDSS J1605. And the virial BH mass ∼7 times higher than the TDE model determined value can be naturally explained by R–L relation determined BLRs sizes very larger than the actual distance of emission regions related to TDEs debris in SDSS J1605. Although no clear conclusion on double-peaked broad lines absolutely related to TDEs, the results here provide clues to detect potential TDEs in AGN with double-peaked broad lines.

Dependence of star formation rate on different properties of molecular clouds

Properties of molecular clouds (MCs) lying in our Galaxy and their star formation scenarios have been investigated with the help of multivariate unsupervised machine learning techniques concerning several observable parameters. At first, the MCs have been classified into four coherent groups using the standard K-means clustering method. Subsequently, the optimum number of groups has been estimated by applying the Elbow method as well as the computation of Silhouette widths for a robustness check. Later, the properties of the groups are studied through several observable parameters as mentioned along with computed ones e.g. star formation rates (SFRs), virial masses, mass-spectra, dynamical time scales (Td), etc. to get a deeper understanding of the star formation process and dynamical evolution of these clouds. It is found that cluster 1 is suitable for the formation of field stars, binary pairs, or stellar associations, whereas the clouds in cluster 2 and cluster 3 are favorable sites for the formation of Galactic clusters of moderate masses, and cluster 4 may produce massive Galactic clusters as well as a few globular clusters. Surprisingly, for each cluster, clouds at around Galacto-centric radius ∼8 kpc, and on the near Galactic plane has a significantly low SFR. These occurrences indicate that the star formation phenomenon has yet not started or the proneness to start in that region.

PHYSICAL PROPERTIES AND KINEMATICS OF DENSE CORES ASSOCIATED WITH REGIONS OF MASSIVE STAR FORMATION FROM THE SOUTHERN SKY

The results of spectral observations in the \( \sim {\kern 1pt} 84{\kern 1pt} - {\kern 1pt} 92\) GHz frequency range of six objects from the southern sky having dense cores and associated with massive star and star cluster forming regions are presented. The observations are carried out with the MOPRA-22m radio telescope. Within the framework of the local thermodynamic equilibrium (LTE) approximation, column densities and abundances of the H13CN, H13CO+, HN13C, HC3N, c-C3H2, SiO, CH3C2H and CH3CN molecules are calculated. Kinetic temperatures (\( \sim 30{\kern 1pt} - {\kern 1pt} 50\) K), sizes of emission regions (\( \sim 0.2{\kern 1pt} - {\kern 1pt} 3.1\) pc) and virial mass esimates (\( \sim 70{\kern 1pt} - {\kern 1pt} 4600{\kern 1pt} {{M}_{ \odot }}\)) are obtained. The linewidths in the three cores decrease with increasing distance from the center. Four cores exhibit asymmetry in the profiles of the optically thick HCO+(1–0) and HCN(1–0) lines, indicating the presence of systematic motions in the line of sight. In two cases, the asymmetry can be caused by contraction of gas. The model HCO+(1–0) and H13CO+(1–0) spectral maps obtained within the non-LTE spherically symmetric model are fitted into observed ones. Radial density (\( \propto {\kern 1pt} {{r}^{{ - 1.6}}}\)), turbulent velocity (\( \propto {\kern 1pt} {{r}^{{ - 0.2}}}\)) and contraction velocity (\( \propto {\kern 1pt} {{r}^{{0.5}}}\)) profiles in the G268.42–0.85 core are obtained. The contraction velocity radial profile differs from expected both in the case of free fall of gas onto a protostar (\({{r}^{{ - 0.5}}}\)), and in the case of global core collapse (contraction velocity does not depend on distance). A discussion of the results obtained is provided.

Gemini near-infrared spectroscopy of high-redshift Fermi blazars: jetted black holes in the early universe were overly massive

ABSTRACT Jetted active galactic nuclei (AGNs) are the principal extragalactic γ-ray sources. Fermi-detected high-redshift (z > 3) blazars are jetted AGNs thought to be powered by massive, rapidly spinning supermassive black holes (SMBHs) in the early universe (<2 Gyr). They provide a laboratory to study early black hole (BH) growth and super-Eddington accretion – possibly responsible for the more rapid formation of jetted BHs. However, previous virial BH masses of z > 3 blazars were based on C iv λ1549 in the observed optical, but C iv λ1549 is known to be biased by strong outflows. We present new Gemini/GNIRS near-infrared spectroscopy for a sample of nine z > 3 Fermi γ-ray blazars with available multiwavelength observations that maximally sample the spectral energy distributions (SEDs). We estimate virial BH masses based on the better calibrated broad H β and/or Mg ii λ2800. We compare the new virial BH masses against independent mass estimates from SED modelling. Our work represents the first step in campaigning for more robust virial BH masses and Eddington ratios for high-redshift Fermi blazars. Our new results confirm that high-redshift Fermi blazars indeed host overly massive SMBHs as suggested by previous work, which may pose a theoretical challenge for models of the rapid early growth of jetted SMBHs.

SDSS-IV MaNGA: the role of the environment in AGN triggering

ABSTRACT The large- and small-scale environments around optically-selected AGN host galaxies and a control sample of non-active galaxies in the MaNGA survey have been investigated in order to evaluate the importance of the environment in AGN triggering. Using the MaNGA integral field spectroscopy, we quantify non-circular motions of the ionized gas and detect an excess of radial gas motions in AGN hosts relative to control galaxies, not associated to AGN feedback and are most likely the result of tidal interactions, possibly associated with the triggering of the AGN. We find that the large-scale environments are similar for the AGN hosts and control galaxies in our sample and are biased towards lower large-scale densities and group virial masses, suggestive that the large-scale environment properties is only relevant to the AGN phenomenon in an indirect way, in the form, e.g. of the morphology-density relation. The small-scale environment, as measured by the frequency and luminosity of close neighbours, was also found to be similar for AGN and control galaxies. However, we find a correlation between the intensity of the non-circular gas motions in AGN hosts and the strength of the tidal field, while the control sample does not present such correlation. Also, AGN hosts with the most intense radial gas motions present larger tidal fields than their control galaxies. These findings indicate that at least a fraction of the AGN hosts in our sample have been triggered by tidal interactions with nearby galaxies.

XQz5: a new ultraluminous z ∼ 5 quasar legacy sample

ABSTRACT Bright quasar samples at high redshift are useful for investigating active galactic nuclei evolution. In this study, we describe XQz5, a sample of 83 ultraluminous quasars in the redshift range 4.5 < z < 5.3 with optical and near-infrared spectroscopic observations, with unprecedented completeness at the bright end of the quasar luminosity function. The sample is observed with the Southern Astrophysical Research Telescope, the Very Large Telescope, and the Australian National University 2.3 m Telescope, resulting in a high-quality, moderate-resolution spectral atlas of the brightest known quasars within the redshift range. We use established virial mass relations to derive the black hole masses by measuring the observed Mg ii λ2799 Å emission line and we estimate the bolometric luminosity with bolometric corrections to the ultraviolet continuum. Comparisons to literature samples show that XQz5 bridges the redshift gap between other X-shooter quasar samples, XQ-100 and XQR-30, and is a brighter sample than both. Luminosity-matched lower redshift samples host more massive black holes, which indicate that quasars at high redshift are more active than their counterparts at lower redshift, in concordance with recent literature.

Taking the Milky Way for a spin: disc formation in the artemis simulations

ABSTRACT We investigate the formation (spin-up) of galactic discs in the artemis simulations of Milky Way (MW)-mass galaxies. In almost all galaxies, discs spin up at higher [Fe/H] than the MW. Those galaxies that contain an analogue of the Gaia Sausage-Enceladus (GSE) spin up at a lower average metallicity than those without. We identify six galaxies with spin-up metallicity similar to that of the MW, which formed their discs ∼8–11 Gyr ago. Five of these experience a merger similar to the GSE. The spin-up times correlate with the halo masses at early times: galaxies with early spin-up have larger virial masses at a lookback time tL = 12 Gyr. The fraction of stars accreted from outside the host galaxy is smaller in galaxies with earlier spin-ups. Accreted fractions small enough to be comparable to the MW are only found in galaxies with the earliest disc formation and large initial virial masses (M200c ≈ 2 × 1011 M⊙ at tL = 12 Gyr). We find that discs form when the halo’s virial mass reaches a threshold of M200c ≈ (6 ± 3) × 1011 M⊙, independent of the spin-up time. However, the failure to form a disc in other galaxies appears to be instead related to mergers at early times. We also find that discs form when the central potential is not particularly steep. Our results indicate that the MW assembled its mass and formed its disc earlier than the average galaxy of a similar mass.

Identifying the discs, bulges, and intra-halo light of simulated galaxies through structural decomposition

ABSTRACT We perform a structural decomposition of galaxies identified in three cosmological hydrodynamical simulations by applying Gaussian mixture models (GMMs) to the kinematics of their stellar particles. We study the resulting disc, bulge, and intra-halo light (IHL) components of galaxies whose host dark matter haloes have virial masses in the range M200 = 1011–$10^{15}\, {\rm M_\odot }$. Our decomposition technique isolates galactic discs whose mass fractions, fdisc, correlate strongly with common alternative morphology indicators; for example, fdisc is approximately equal to κco, the fraction of stellar kinetic energy in corotation. The primary aim of our study, however, is to characterize the IHL of galaxies in a consistent manner and over a broad mass range, and to analyse its properties from the scale of galactic stellar haloes up to the intra-cluster light. Our results imply that the IHL fraction, fIHL, has appreciable scatter and is strongly correlated with galaxy morphology: at fixed stellar mass, the IHL of disc galaxies is typically older and less massive than that of spheroids. Above $M_{200}\approx 10^{13}\, {\rm M_\odot }$, we find, on average, fIHL ≈ 0.37, albeit with considerable scatter. The transition radius beyond which the IHL dominates the stellar mass of a galaxy is roughly $30\, {\rm kpc}$ for disc galaxies, but depends strongly on halo mass for spheroids. However, we find that no alternative IHL definitions – whether based on the ex situ stellar mass, or the stellar mass outside a spherical aperture – reproduce our dynamically defined IHL masses.

Catalogue of model star clusters in the Milky Way and M31 galaxies

ABSTRACT Detailed understanding of the formation and evolution of globular clusters (GCs) has been recently advanced through a combination of numerical simulations and analytical models. We employ a state-of-the-art model to create a comprehensive catalogue of simulated clusters in three Milky Way (MW) and three Andromeda (M31) analogue galaxies. Our catalogue aims to connect the chemical and kinematic properties of GCs to the assembly histories of their host galaxies. We apply the model to a selected sample of simulated galaxies that closely match the virial mass, circular velocity profile, and defining assembly events of the MW and M31. The resulting catalogue has been calibrated to successfully reproduce key characteristics of the observed GC systems, including total cluster mass, mass function, metallicity distribution, radial profile, and velocity dispersion. We find that clusters in M31 span a wider range of age and metallicity, relative to the MW, possibly due to M31’s recent major merger. Such a merger also heated up the in-situ GC population to higher orbital energy and introduced a large number of ex-situ clusters at large radii. Understanding the impacts of galaxy mergers and accretion on the GC populations is crucial for uncovering the galaxy assembly histories.

The compactness of ultra-faint dwarf galaxies: A new challenge?

So far, numerical simulations of ultra-faint dwarf galaxies (UFDs) have failed to properly reproduce the observed size–luminosity relation. In particular, no hydrodynamical simulation run has managed to form UFDs with a half-light radius as small as 30 pc, as seen in observations of several UFD candidates. We tackle this problem by developing a simple but numerically clean and powerful method in which predictions of the stellar content of UFDs from ΛCDM cosmological hydrodynamical simulations are combined with very high-resolution dark-matter-only runs. This method allows us to trace the buildup history of UFDs and to determine the impact of the merger of building-block objects on their final size. We find that, while no UFDs more compact than 20 pc can be formed, slightly larger systems are only reproduced if all member stars originate from the same initial mini-halo. However, this imposes that (i) the total virial mass is smaller than 3 × 108 M⊙, and (ii) the stellar content prior to the end of the reionisation epoch is very compact (< 15 pc) and strongly gravitationally bound, which is a challenge for current hydrodynamical numerical simulations. If initial stellar building blocks are larger than 35 pc, the size of the UFD will extend to 80 pc. Finally, our study shows that UFDs keep strong imprints of their buildup history in the form of elongated or extended stellar halos. Those features can erroneously be interpreted as tidal signatures.

Towards accurate field-level inference of massive cosmic structures

ABSTRACT We investigate the accuracy requirements for field-level inference of cluster and void masses using data from galaxy surveys. We introduce a two-step framework that takes advantage of the fact that cluster masses are determined by flows on larger scales than the clusters themselves. First, we determine the integration accuracy required to perform field-level inference of cosmic initial conditions on these large scales by fitting to late-time galaxy counts using the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. A 20-step COLA integrator is able to accurately describe the density field surrounding the most massive clusters in the local super-volume ($\lt 135\, {h^{-1}\mathrm{\, Mpc}}$), but does not by itself lead to converged virial mass estimates. Therefore, we carry out ‘posterior resimulations’, using full N-body dynamics while sampling from the inferred initial conditions, and thereby obtain estimates of masses for nearby massive clusters. We show that these are in broad agreement with existing estimates, and find that mass functions in the local super-volume are compatible with ΛCDM.

SDSS J1619 with blueshifted broad components in H α and in [O iii] having similar line width and velocity shifts: a recoiling SMBH candidate?

ABSTRACT In this letter, we report a potential candidate of recoiling supermassive black hole (rSMBH) in Sloan Digital Sky Survey (SDSS) J1619 based on similar velocity shifts and line widths of the blueshifted broad components in H α and [O iii] doublet. The measured line width ratio between blueshifted broad H α and broad [O iii] line is 1.06, if compared with common values around 5.12 for normal Type-1 active galactic nuclei, indicating different properties of the blueshifted broad components in SDSS J1619 from those of normal Quasi Stellar Objects (QSOs). The virial BH mass MBHr derived from the broad H α is consistent with the mass expected from the MBH–σ relation. The similar velocity shifts and line widths of the blueshifted broad components in H α and [O iii] and the virial BH mass derived from the H α broad line emissions that is consistent with the mass expected from the MBH–σ relation, can be explained by an rSMBH scenario. Besides the rSMBH scenario, either the similar line widths of the blueshifted broad components in H α and in [O iii] or the consistency between the virial BH mass and the mass expected from the MBH–σ relation cannot be explained by the other proposed models in SDSS J1619.

BASS. XXXV. The M BH–σ* Relation of 105 Month Swift-BAT Type 1 AGNs

We present two independent measurements of stellar velocity dispersions (σ ⋆) from the Ca ii H+K λ3969, 3934 and Mg i b λ 5183, 5172, 5167 region (3880–5550 Å) and the calcium triplet region (8350–8750 Å) for 173 hard X-ray-selected Type 1 active galactic nuclei (AGNs; z ≤ 0.08) from the 105 month Swift-BAT catalog. We construct one of the largest samples of local Type 1 AGNs that have both single-epoch virial black hole mass (M BH) estimates and σ ⋆ measurements obtained from high spectral resolution data, allowing us to test the usage of such methods for supermassive black hole studies. We find that the two independent σ ⋆ measurements are highly consistent with each other, with an average offset of only 0.002 ± 0.001 dex. Comparing M BH estimates based on broad emission lines and stellar velocity dispersion measurements, we find that the former is systematically lower by ≈0.12 dex. Consequently, Eddington ratios estimated through broad-line M BH determinations are similarly biased (but in the opposite way). We argue that the discrepancy is driven by extinction in the broad-line region. We also find an anticorrelation between the offset from the M BH–σ ⋆ relation and the Eddington ratio. Our sample of Type 1 AGNs shows a shallower M BH–σ ⋆ relation (with a power-law exponent of ≈3.5) compared with that of inactive galaxies (with a power-law exponent of ≈4.5), confirming earlier results obtained from smaller samples.

The MUSE-Faint survey

Aims. We use the stellar line-of-sight velocities of Antlia B (Ant B), a faint dwarf galaxy in the NGC 3109 association, to derive constraints on the fundamental properties of scalar field dark matter (SFDM), which was originally proposed to solve the small-scale problems faced by cold dark matter models. Methods. We used the first spectroscopic observations of Ant B, a distant (d ∼ 1.35 Mpc) faint dwarf (MV = −9.7, M⋆ ∼ 8 × 105 M⊙), from MUSE-Faint, a survey of ultra-faint dwarfs conducted using the Multi Unit Spectroscopic Explorer. By measuring the line-of-sight velocities of stars in the 1′×1′ field of view, we identified 127 stars as members of Ant B, which enabled us to model its dark matter density profile with the Jeans modelling code GRAVSPHERE. We implemented a model for SFDM into GRAVSPHERE and used this to place constraints on the self-coupling strength of this model. Results. We find a virial mass of M200 ≈ 1.66−0.92+2.51 × 109 M⊙ and a concentration parameter of c200 ≈ 17.38−4.20+6.06 for Ant B. These results are consistent with the mass-concentration relations in the literature. We constrain the characteristic length scale of the repulsive self-interaction RTF of the SFDM model to RTF ≲ 180 pc (68% confidence level), which translates to a self-coupling strength of g/m2c4 ≲ 5.2 × 10−20 eV−1 cm3. The constraint on the characteristic length scale of the repulsive self-interaction is inconsistent with the value required to match observations of the cores of dwarf galaxies in the Local Group, suggesting that the cored density profiles of those galaxies are not caused by SFDM.

WALLABY pre-pilot survey: ultra-diffuse galaxies in the Eridanus supergroup

ABSTRACT We present a pilot study of the atomic neutral hydrogen gas (H i) content of ultra-diffuse galaxy (UDG) candidates. In this paper, we use the pre-pilot Eridanus field data from the Widefield ASKAP L-band Legacy All-sky Blind Survey to search for H i in UDG candidates found in the Systematically Measuring Ultra-diffuse Galaxies survey (SMUDGes). We narrow down to 78 SMUDGes UDG candidates within the maximum radial extents of the Eridanus subgroups for this study. Most SMUDGes UDGs candidates in this study have effective radii smaller than 1.5 kpc and thus fail to meet the defining size threshold. We only find one H i detection, which we classify as a low-surface-brightness dwarf. Six putative UDGs are H i-free. We show the overall distribution of SMUDGes UDG candidates on the size–luminosity relation and compare them with low-mass dwarfs on the atomic gas fraction versus stellar mass scaling relation. There is no correlation between gas-richness and colour indicating that colour is not the sole parameter determining their H i content. The evolutionary paths that drive galaxy morphological changes and UDG formation channels are likely the additional factors to affect the H i content of putative UDGs. The actual numbers of UDGs for the Eridanus and NGC 1332 subgroups are consistent with the predicted abundance of UDGs and the halo virial mass relation, except for the NGC 1407 subgroup, which has a smaller number of UDGs than the predicted number. Different group environments suggest that these putative UDGs are likely formed via the satellite accretion scenario.

Shaping the unseen: the influence of baryons and environment on low-mass, high-redshift dark matter haloes in the SIEGE simulations

ABSTRACT We use zoom-in, hydrodynamical, cosmological N-body simulations tracing the formation of the first stellar clumps from the SImulating the Environments where Globular clusters Emerged project, to study key structural properties of dark matter haloes when the Universe was only $0.92\, {\rm Gyr}$ old. The very high resolution (maximum physical resolution $0.3\, {h}^{-1}\, {\rm pc}$ at z = 6.14, smallest dark matter particle mass $164\, {\rm M}_{\odot }$) allows us to reach the very low mass end of the stellar-to-halo mass relation ($M_{\rm vir}=10^{7.5{\!-\!}9.5}\, {\rm M}_{\odot }$) to study the processes that mould dark matter haloes during the first stages of structure formation. We investigate the role of baryonic cooling and stellar feedback, modelled from individual stars, in shaping haloes, and of environmental effects as accretion of dark matter along cosmic filaments and mergers. We find that the onset of star formation (typically for $\log M_{\rm vir}/\, {\rm M}_{\odot }\simeq 7.6$) causes the inner cusp in the haloes’ density profile to flatten into a core with constant density and size proportionally to the halo virial mass. Even at these mass scales, we confirm that baryons make haloes that have formed stars rounder in the central regions than haloes that have not formed stars yet, with median minor-to-major 〈q〉 and intermediate-to-major 〈s〉 axes 0.66 and 0.84, respectively. Our morphological analysis shows that, at z = 6.14, haloes are largely prolate in the outer parts, with the major axis aligned along filaments of the cosmic web or towards smaller sub-haloes, with the degree of elongation having no significant dependence on the halo mass.

Spurious heating of stellar motions by dark matter particles in cosmological simulations of galaxy formation

ABSTRACT We use two cosmological simulations to study the impact of spurious heating of stellar motions within simulated galaxies by dark matter (DM) particles. The simulations share the same numerical and subgrid parameters, but one used a factor of 7 more DM particles. Many galaxy properties are unaffected by spurious heating, including their masses, star formation histories, and the spatial distribution of their gaseous baryons. The distribution and kinematics of stellar and DM particles, however, are affected. Below a resolution-dependent virial mass, $M_{200}^{\rm spur}$, galaxies have higher characteristic velocities, larger sizes, and more angular momentum in the simulation with lower DM mass resolution; haloes have higher central densities and lower velocity dispersions. Above $M_{200}^{\rm spur}$, galaxies and haloes have similar properties in both runs. The differences arise due to spurious heating, which transfers energy from DM to stellar particles, causing galaxies to heat up and haloes to cool down. The value of $M_{200}^{\rm spur}$ can be derived from an empirical disc heating model, and coincides with the mass below which the predicted spurious velocity dispersion exceeds the measured velocity dispersion of simulated galaxies. We predict that galaxies in the $100^3\, {\rm Mpc}^3$eagle run and IllustrisTNG-100 are robust to spurious collisional effects at their half-mass radii provided $M_{200}^{\rm spur}\approx 10^{11.7}\, {\rm M_\odot }$; for the $25^3\, {\rm Mpc}^3$eagle run and IllustrisTNG-50, we predict $M_{200}^{\rm spur}\approx 10^{11}\, {\rm M_\odot }$. Suppressing spurious heating at smaller/larger radii, or for older/younger stellar populations, requires haloes to be resolved with more/fewer DM particles.

A physical and concise halo model based on the depletion radius

ABSTRACT We develop a self-consistent and accurate halo model by partitioning matter according to the depletion radii of haloes. Unlike conventional models that define haloes with the virial radius while relying on a separate exclusion radius or ad hoc fixes to account for halo exclusion, our model distributes mass across all scales self-consistently and accounts for both the virialized and non-virialized matter distribution around each halo. Using a cosmological simulation, we show that our halo definition leads to very simple and intuitive model components, with the one-halo term given by the Einasto profile with no truncation needed, and the halo–halo correlation function following a universal power-law form down to the halo boundary. The universal halo–halo correlation also allows us to easily model the distribution of unresolved haloes as well as diffuse matter. Convolving the halo profile with the halo–halo correlation function, we obtain a complete description of the halo–matter correlation across all scales, which self-consistently accounts for halo exclusion at the transition scale. Mass conservation is explicitly maintained in our model, and the scale dependence of the classical halo bias is easily reproduced. Our model can successfully reconstruct the halo–matter correlation function within an accuracy of 9 per cent for halo virial masses in the range of 1011.5h−1 M⊙ < Mvir < 1015.35h−1 M⊙ at z = 0, and covers the radial range of 0.01 h−1 Mpc < r < 20 h−1 Mpc. We also show that our model profile can accurately predict the characteristic depletion radius at the minimum bias and the splash-back radius at the steepest density slope locations.

The Seoul National University AGN Monitoring Project. IV. Hα Reverberation Mapping of Six AGNs and the Hα Size–Luminosity Relation

The broad-line region (BLR) size–luminosity relation has paramount importance for estimating the mass of black holes in active galactic nuclei (AGNs). Traditionally, the size of the Hβ BLR is often estimated from the optical continuum luminosity at 5100 Å, while the size of the Hα BLR and its correlation with the luminosity is much less constrained. As a part of the Seoul National University AGN Monitoring Project, which provides 6 yr photometric and spectroscopic monitoring data, we present our measurements of the Hα lags of high-luminosity AGNs. Combined with the measurements for 42 AGNs from the literature, we derive the size–luminosity relations of the Hα BLR against the broad Hα and 5100 Å continuum luminosities. We find the slope of the relations to be 0.61 ± 0.04 and 0.59 ± 0.04, respectively, which are consistent with the Hβ size–luminosity relation. Moreover, we find a linear relation between the 5100 Å continuum luminosity and the broad Hα luminosity across 7 orders of magnitude. Using these results, we propose a new virial mass estimator based on the Hα broad emission line, finding that the previous mass estimates based on scaling relations in the literature are overestimated by up to 0.7 dex at masses lower than 107 M ⊙.

Looking for Traces of Nonminimally Coupled Dark Matter in the X-COP Galaxy Clusters Sample

We look for possible evidence of a nonminimal coupling (NMC) between dark matter (DM) and gravity using data from the X-COP compilation of galaxy clusters. We consider a theoretically motivated NMC that may dynamically arise from the collective behavior of the coarse-grained DM field (e.g., via Bose–Einstein condensation) with averaging/coherence length L NMC. In the Newtonian limit, the NMC modifies the Poisson equation by a term proportional to the Laplacian of the DM density itself. We show that this term, when acting as a perturbation over the standard Navarro–Frenk–White (NFW) profile of cold DM particles, can yield DM halo density profiles capable of correctly fitting galaxy clusters’ pressure profiles with an accuracy comparable to and, in some cases, even better than the standard cold DM NFW profile. We also show that the observed relation between the NMC length scale and the virial mass found in Gandolfi et al. for late-type galaxies is consistent with the relation we find in the current work, suggesting that the previously determined power-law scaling law holds up to galaxy cluster mass scales.