分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The conditions under which galactic nuclear regions become active are largely
unknown, although it has been hypothesized that secular processes related to
galaxy morphology could play a significant role. We investigate this question
using optical i-band images of 3096 SDSS quasars and galaxies at 0.3
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The correlation between the mass of supermassive black holes (SMBHs; $\mathcal{M}_{\rm BH}$) and their host galaxies ($\mathcal{M}_\star$) in the reionization epoch provides valuable constraints on their early growth. High-redshift quasars typically have a $\mathcal{M}_{\rm BH}$/$\mathcal{M}_\star$ ratio significantly elevated in comparison to the local value. However, the degree to which this apparent offset is driven by observational biases is unclear for the most distant quasars. To address this issue, we model the sample selection and measurement biases for a compilation of 20 quasars at $z\sim6$ with host properties based on ALMA observations. We find that the observed distribution of quasars in the $\mathcal{M}_{\rm BH} - \mathcal{M}_\star$ plane can be reproduced by assuming that the underlying SMBH population at $z\sim6$ follows the relationship in the local universe. However, a positive or even a negative evolution in $\mathcal{M}_{\rm BH}$/$\mathcal{M}_\star$ can also explain the data, depending on whether the intrinsic scatter evolves and the strength of various systematic uncertainties. To break these degeneracies, an improvement in the accuracy of mass measurements and an expansion of the current sample to lower $\mathcal{M}_{\rm BH}$ limits are needed. Furthermore, assuming a radiative efficiency of 0.1 and quasar duty cycles estimated from the active SMBH fraction, significant outliers in $\mathcal{M}_{\rm BH}$/$\mathcal{M}_\star$ tend to move toward the local relation given their instantaneous BH growth rate and star formation rate. This may provide evidence for a self-regulated SMBH-galaxy coevolution scenario that is in place at $z\sim6$, with AGN feedback being a possible driver.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Recent high-$z$ quasar observations strongly indicate that super-Eddington accretion is a crucial phase to describe the existence of supermassive black holes (SMBHs) with $M_\mathrm{BH} \gtrsim 10^9 M_\odot$ at $z \gtrsim 7$. Motivated by the theoretical suggestion that the super-Eddington phase efficiently produces outflows and jets bright in radio bands, we search and find a super-Eddington radio-loud dust-obscured galaxy (DOG) J1406+0102 at $z=0.236$, through cross-matching of the infrared-bright DOGs of Noboriguchi et al. (2019) with the VLA/FIRST 1.4 GHz radio and the SDSS optical spectral catalog. DOG J1406+0102 shows broad components in the Balmer lines. Assuming those lines are from the broad line region, it gives BH mass estimation of $\log\ (M_\mathrm{BH}/M_\odot)=7.30 \pm 0.25$, and AGN luminosity of $\log (L_\mathrm{bol,[OIII]}/\mathrm{erg}~\mathrm{s}^{-1}) = 45.91\pm0.38$ estimated from the intrinsic [OIII] luminosity, resulting in super-Eddington accretion of $\lambda_\mathrm{Edd}\simeq 3$. We show that 1) DOG J1406+0102 is operating strong AGN feedback: the [OIII] outflow velocity exceeds the escape velocity of the host galaxy halo and the kinetic efficiency is obtained as $\approx$ 8% that can be sufficient to quench the host galaxy, 2) the expected future growth pathway of DOG J1406+0102 would join an over-massive BH trajectory and 3) radio-loud DOGs can provide a significant contribution to the high-energy ($\gtrsim$ 100 TeV) cosmic neutrino background if we assume DOG J1406+0102 as a representative of radio-loud DOGs.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We investigate the variation in the mid-infrared spectral energy distributions of 373 low-redshift ($z<0.4$) star-forming galaxies, which reflects a variety of polycyclic aromatic hydrocarbon (PAH) emission features. The relative strength of PAH emission is parameterized as $q_\mathrm{PAH}$, which is defined as the mass fraction of PAH particles in the total dust mass. With the aid of continuous mid-infrared photometric data points covering 7-24$\mu$m and far-infrared flux densities, $q_\mathrm{PAH}$ values are derived through spectral energy distribution fitting. The correlation between $q_\mathrm{PAH}$ and other physical properties of galaxies, i.e., gas-phase metallicity ($12+\mathrm{log(O/H)}$), stellar mass, and specific star-formation rate (sSFR) are explored. As in previous studies, $q_\mathrm{PAH}$ values of galaxies with high metallicity are found to be higher than those with low metallicity. The strength of PAH emission is also positively correlated with the stellar mass and negatively correlated with the sSFR. The correlation between $q_\mathrm{PAH}$ and each parameter still exists even after the other two parameters are fixed. In addition to the PAH strength, the application of metallicity-dependent gas-to-dust mass ratio appears to work well to estimate gas mass that matches the observed relationship between molecular gas and physical parameters. The result obtained will be used to calibrate the observed PAH luminosity-total infrared luminosity relation, based on the variation of MIR-FIR SED, which is used in the estimation of hidden star formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} < 23$), while the other shows signs of moderate absorption ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy distribution (SED) modelling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV X-ray luminosities of ${\sim}10^{\text{44--45}}\,\mathrm{erg\ s^{-1}}$) and star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes (SMBHs) in the high-redshift universe.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We use machine learning techniques to investigate their performance in classifying active galactic nuclei (AGNs), including X-ray selected AGNs (XAGNs), infrared selected AGNs (IRAGNs), and radio selected AGNs (RAGNs). Using known physical parameters in the Cosmic Evolution Survey (COSMOS) field, we are able to well-established training samples in the region of Hyper Suprime-Cam (HSC) survey. We compare several Python packages (e.g., scikit-learn, Keras, and XGBoost), and use XGBoost to identify AGNs and show the performance (e.g., accuracy, precision, recall, F1 score, and AUROC). Our results indicate that the performance is high for bright XAGN and IRAGN host galaxies. The combination of the HSC (optical) information with the Wide-field Infrared Survey Explorer (WISE) band-1 and WISE band-2 (near-infrared) information perform well to identify AGN hosts. For both type-1 (broad-line) XAGNs and type-1 (unobscured) IRAGNs, the performance is very good by using optical to infrared information. These results can apply to the five-band data from the wide regions of the HSC survey, and future all-sky surveys.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We investigate the physical properties, such as star-forming activity, disk
vs. bulge nature, galaxy size, and obscuration of 3796 X-ray selected AGNs at
$0.2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The relationship between quasars and their host galaxies provides clues on
how supermassive black holes (SMBHs) and massive galaxies are jointly
assembled. To elucidate this connection, we measure the structural and
photometric properties of the host galaxies of ~5000 SDSS quasars at 0.2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We measure the evolution of the $M_{\rm BH}-M_*$ relation using 584
uniformly-selected SDSS quasars at $0.2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Which galaxies in the general population turn into active galactic nuclei
(AGN) is a keystone of galaxy formation and evolution. Thanks to SRG/eROSITA's
contiguous 140 square degrees pilot survey field, we constructed a large,
complete, and unbiased soft X-ray flux-limited AGN sample at low redshift
$0.05
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We construct the eROSITA X-ray catalog of radio galaxies discovered by the
WERGS survey that is made by the cross-matching of the wide-area Subaru/HSC
optical survey and VLA/FIRST 1.4 GHz radio survey. We find 393 eROSITA detected
radio galaxies in the 0.5--2 keV band in the eFEDS field covering 140~deg$^2$.
Thanks to the wide and medium depth eFEDS X-ray survey, the sample contains the
rare and most X-ray luminous radio galaxies above the knee of the X-ray
luminosity function, spanning 4422$. Those obscured
and radio AGN reside in $0.4
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report on a spectroscopic program to search for dual quasars using Subaru Hyper Suprime-Cam (HSC) images of SDSS quasars which represent an important stage during galaxy mergers. Using Subaru/FOCAS and Gemini-N/GMOS, we identify three new physically associated quasar pairs having projected separations less than 20 kpc, out of 26 observed candidates. These include the discovery of the highest redshift ($z=3.1$) quasar pair with a separation $<$ 10 kpc. Based on the sample acquired to date, the success rate of identifying physically associated dual quasars is $19\%$ when excluding stars based on their HSC colors. Using the full sample of six spectroscopically confirmed dual quasars, we find that the black holes in these systems have black hole masses ($M_{BH} \sim 10^{8-9}M_{\odot}$) similar to single SDSS quasars as well as their bolometric luminosities and Eddington ratios. We measure the stellar mass of their host galaxies based on 2D image decomposition of the five-band ($grizy$) optical emission and assess the mass relation between supermassive black holes (SMBHs) and their hosts. Dual SMBHs appear to have elevated masses relative to their host galaxies. Thus mergers may not necessarily align such systems onto the local mass relation, as suggested by the Horizon-AGN simulation. This study suggests that dual luminous quasars are triggered prior to the final coalescence of the two SMBHs, resulting in early mass growth of the black holes relative to their host galaxies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The existence of high-redshift supermassive black holes (SMBHs) -- shining brightly as quasars during the first billion years of our universe -- presents a conundrum in astrophysics. A broad variety of physical mechanisms have been proposed for the formation and rapid growth of these early SMBHs. Promising diagnostics are the relative properties of the black hole and its host galaxy. However, up to now, the detection of stars in quasar host galaxies has been elusive beyond $z>2$, even with deep HST observations. Here, we report the first detections of the stellar component of the host galaxies of two relatively low-luminosity quasars at $z>6$ observed with JWST using NIRCam. After modeling and subtracting the glare from the quasar itself, we find that the host galaxies are massive (stellar mass of $2.5\times$ and $6.3\times10^{10}$ M$_{\odot}$), compact, and disk-like. Unlike most SMBHs in the nearby universe, these quasars are displaced from the centers of their host galaxies in the rest-frame optical, in one case by $0.9$ kpc. These first positive detections of quasar hosts at $z>6$ are a pivotal milestone; we can now assess the stellar environment along with star formation and black hole accretion to determine the physical conditions that govern the formation and evolution of the first SMBHs.