arXiv subjects

Toru Misawa

Publications and source records attributed to Toru Misawa.

At least 19 recordsLinked to original sources

arXiv2026

H I Absorbers as Beacons of Hidden Structure at $z \sim 3$: Multi-Component, Metal-Rich Absorption System near a Protocluster

H I gas traces the large-scale structure and provides the primary fuel for star formation. High-$z$ protoclusters are ideal laboratories to study how H I gas is accreted and consumed during the formation of the most massive structures in the Universe. However, much remains unknown about the distribution and physical state of their H I gas. We examine a rare configuration in which a protocluster candidate is located in front of a quasar at $z=3.09$. Our spectroscopic campaign confirms a protocluster at $z=3.079$: however, no corresponding strong H I absorption is found in the background quasar spectrum. Instead, we serendipitously discover a prominent H I absorption feature at $z\sim 3.01$, offset by $\sim 60$ cMpc from the centre of the protocluster. Spanning an exceptionally broad velocity range of $\sim 2000$ km s$^{-1}$ ($\sim 40$ cMpc), this absorption is decoupled from the confirmed member galaxies. Detailed kinematic modelling reveals this absorption comprises five distinct components rather than a single cloud. Moreover, one of these components exhibits a super-solar metallicity ($[\mathrm{O/H}] = +1.19^{+0.91}_{-0.78}$). We propose two physical scenarios for this unique system: (1) an additional, hidden massive protocluster along the line of sight, and/or (2) metal-rich outflows and metal-poor inflows driven by a single massive galaxy. The discovery highlights that while protoclusters are not universally associated with strong H I absorption, targeting the strong H I absorbers may serve as a beacon for uncovering massive, metal-rich protoclusters or complex gas kinematics in the early Universe.

astro-ph.GA↗

arXiv2026

GREX-PLUS Science Book v2

GREX-PLUS (Galaxy Reionization EXplorer and PLanetary Universe Spectrometer) is a mission candidate for a JAXA strategic L-class mission to be launched in the 2030s. Its primary science goals are two-fold: galaxy formation and evolution, and planetary system formation and evolution. The GREX-PLUS spacecraft will carry a telescope with a 1 m primary mirror aperture cooled down to 50 K. The two science instruments will be onboard: a wide-field camera in the 2--8 $\mu$m wavelength band and a high-resolution spectrometer with a wavelength resolution of 30,000 in the 10--18 $\mu$m band. The GREX-PLUS wide-field camera aims to detect the first generation of galaxies at redshift $z>15$. The GREX-PLUS high-resolution spectrometer aims to identify the location of the water ``snowline'' in protoplanetary disks. Both instruments will provide unique datasets for a broad range of scientific topics, including galaxy mass assembly, the origin of supermassive blackholes, infrared background radiation, molecular spectroscopy in the interstellar medium, transit spectroscopy of exoplanet atmospheres, planetary atmospheres in the Solar System, and so on. This document is the second version of a collection of scientific themes that can be achieved with GREX-PLUS. Each section in Chapters~2 and 3 is based on presentations at several GREX-PLUS Science Workshops.

astro-ph.IM↗

arXiv2026

Blackbody Quasar and Radio Source (BBQSORS): A Candidate of Transitional Little Red Dots with a $T\sim10^4\ K$ Blackbody Spectrum

We report Subaru/PFS spectroscopic follow-up of a radio-loud quasar at $z=1.715$ from the UNVEIL radio AGN catalog and with X-ray detections. The PFS spectrum displays a broad MgII emission line with an $\mathrm{FWHM}\gtrsim4000\ km/s$, accompanied by a narrow absorption feature. The spectrum reveals a characteristic $\Lambda$-shape over the rest-frame wavelength ranging $\sim1500-3500\ \r{A}$. This underlying UV continuum is too curved to be reproduced by simply applying dust extinction to the spectrum of typical unobscured quasars. Alternatively, it is well described by a blackbody spectrum with a temperature of $T\approx10000\ K$. This result is in good agreement with its UV to MIR photometry that can be well modeled by three blackbody components representing the SMBH envelope ($\mathit{T}\approx9700\ K$), dust torus ($T\approx1500\ K$), and host galaxy dust ($T\approx80\ K$). The source is marginally detected in the GALEX NUV, revealing a potential V-shaped spectral energy distribution around $1400\ \r{A}$, reminiscent of the spectral feature reported for recently discussed LRDs whose V-shapes occur around $3000-4000\ \r{A}$. This wavelength shift is broadly consistent with the temperature contrast between our blackbody component, with $T\sim10^4\ K$, and the lower effective temperature of $T\sim5000\ K$ expected for an optically thick photosphere surrounding the SMBH in LRDs. These properties suggest that this source might be caught in a transient evolutionary phase in which the dense gas envelope characteristic of LRD has begun to fragment, allowing us to witness the emergence of a quasar from an LRD-like state.

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arXiv2025

Reporting a Deficit of Intrinsic NV Absorbers in Core-dominated, Radio-loud Quasars

We searched the Hubble Space Telescope Cosmic Origins Spectrograph archive for ultraviolet spectra of 428 AGN to identify intrinsic NV absorption systems. We filtered out Type 2 AGN, blazars, and spectra that do not cover at least part of the velocity window from 5000 km/s blueward to 5000 km/s redward (hereafter, the ``associated'' region) of the NV emission line. This yielded 175 Type 1 quasars, 34 radio-loud, 133 radio-quiet, and eight unconstrained. Our survey uncovered 77 associated NV systems in the spectra of 48 of these low-redshift quasars. We consider the incidence of intrinsic absorbers as a function of quasar properties (optical, radio and X-ray). We find a statistically significant dearth of intrinsic NV systems in the spectra of the 34 radio-loud quasars (6%), compared to 29% of the 133 radio-quiet quasars containing at least one intrinsic system. Assuming intrinsic systems are equally likely to occur in radio-loud and radio-quiet quasars and the orientations of the two subsamples are comparable, there is a 0.1% probability of such a deficit occurring by chance in the radio-loud population. We propose that this deficit of systems is caused by orientation effects. FIRST radio images are available for 14 of the 33 radio-loud quasars. These show that only three of the 14 radio-loud quasars have lobe-dominated morphologies, whereas 11 of the 14 radio-loud quasars have compact radio morphologies, implying that these quasars are face on, and suggesting that clouds that produce NV absorption are rarely found along the polar axis.

astro-ph.CO↗

arXiv2025

An Extremely-High Velocity Outflow in SMSS J2157-3602, the most luminous quasar in the first 1.3 Gyr

We report the discovery of an extremely high-velocity outflow (EHVO) in the most luminous ($L\rm_{Bol}$ $\sim$ 2.29 $\times$ 10$^{48}$ erg/s) QSO, SMSS J2157-3602, at z=4.692. Combined XSHOOTER and NIRES observations reveal that the EHVO reaches a maximum velocity of v$_\mathrm{max} \sim 0.13c$ and persists over rest-frame timescales of a few months to one year. SMSS J2157-3602 also exhibits one of the highest balnicity index discovered in an EHVO so far. In addition, the blueshifted CIV emission traces a high-velocity (v$\rm_{CIV}^{50}\sim$ 4660 km/s) outflow from the broad-line region. Thanks to an XMM-Newton observation, we also discover the X-ray weak nature of this QSO, which likely prevents the overionization of the innermost disk atmosphere and facilitates the efficient launch of the detected EHVO and BLR winds. The extraordinary luminosity of SMSS J2157-3602 and the extreme velocity of the EHVO make it a unique laboratory for testing AGN driven feedback under extreme conditions. Current uncertainties on the outflow's location and column density strengthen the case for dedicated follow-up, which will be essential to assess the full feedback potential of this remarkable quasar.

astro-ph.GA↗

arXiv2025

AGN Feedback Efficiency of NAL Quasars

We consider if outflowing winds that are detected via narrow absorption lines (NALs) with FWHM of $<$ 500 km/s (i.e., NAL outflows) in quasar spectra contribute to feedback. As our sample, we choose 11 NAL systems in eight optically luminous quasars from the NAL survey of Misawa et al. (2007a), based on the following selection criteria: i) they exhibit ``partial coverage'' suggesting quasar origin (i.e., intrinsic NALs), ii) they have at least one low-ionization absorption line (C II and/or Si II), and iii) the Ly$\alpha$ absorption line is covered by available spectra. The results depend critically on this selection method, which has caveats and uncertainties associated with it, as we discuss in a dedicated section of the paper. Using the column density ratio of the excited and ground states of C II and Si II, we place upper limits on the electron density as $n_{\rm e}$ $<$ 0.2 - 18 cm$^{-3}$ and lower limits on their radial distance from the flux source $R$ as greater than several hundreds of kpc. We also calculate lower limits on the mass outflow rate and kinetic luminosity of $\log(\dot{M}/{\rm M_{\odot}~s}^{-1}) > 79$ - (3.1$\times 10^{5})$ and $\log(\dot{E_{\rm k}}/{\rm erg~s}^{-1}) > 42.9$ - 49.8, respectively. Taking the NAL selection and these results at face value, the inferred feedback efficiency can be comparable to or even larger than those of broad absorption line and other outflow classes, and large enough to generate significant AGN feedback. However, the question of the connection of quasar-driven outflows to NAL absorbers at large distances from the central engine remains open and should be addressed by future theoretical work.

astro-ph.GA↗

arXiv2025

The first direct imaging of the silhouette of a damped Lyman $\alpha$ system along the line-of-sight to a background galaxy

The H~{\sc i} gas distribution in damped Lyman $\alpha$ absorbers (DLAs) has remained elusive due to the point-source nature of background quasar emission. Observing DLAs against spatially extended background galaxies provides a new method for constraining their size and structure. Using the Keck Cosmic Web Imager, we present the first ``silhouette'' image of a DLA at $z=3.34$, identified in the spectrum of a background galaxy at $z=3.61$. Although the silhouette remains unresolved due to limited spatial resolution, this represents a successful proof-of-concept for studying DLA morphology using extended background sources. Possible residual emission in the DLA trough suggests an optical depth contrast exceeding $10^7$ in the internal structure, implying a sharp edge or patchy structure. A Lyman $\alpha$ emitter (LAE) at $z_{\rm LAE}=3.3433\pm0.0005$, consistent with the DLA redshift, is detected at an angular separation of $1.''73\pm0.''28$ ($12.9\pm2.1$ kpc). The DLA is surrounded by three galaxies within 140 kpc in projected distance and 500 km s$^{-1}$ in line-of-sight velocity, indicating that it resides in the circumgalactic medium of the LAE or within a galaxy group/protocluster environment. An O~{\sc i} $\lambda1302$ absorption at $z_{\rm OI}=3.3288\pm0.0004$ is also detected along the line of sight. This absorber may trace metal-enriched outflow from the LAE or a gas-rich galaxy exhibiting the highest star formation activity among the surrounding galaxies. Future large spectroscopic surveys of galaxies will expand such a DLA sample, and three-dimensional spectroscopy for it will shed new light on the role of intergalactic dense gas in galaxy formation and evolution.

astro-ph.CO↗

arXiv2024

The possible long-term periodic variability of the extremely luminous quasar WISE J090924.01+000211.1

The extremely luminous infrared galaxy (ELIRG), WISE J090924.01+000211.1 (hereafter; WISE J0909+0002, $z=1.87$) is an extraordinary object with a quasar aspect. This study performs monitoring observations of WISE J0909+0002 with the 105 cm Murikabushi telescope, Okayama and Akeno 50 cm telescopes/MITSuME ($g'$, $R_{\rm c}$, and $I_{\rm c}$ bands), and the SaCRA 55 cm telescope/MuSaSHI ($r$, $i$, and $z$ bands). We obtain the following results by combining the UV/optical light curves of the CRTS, Pan-STARRS, and ZTF archive data, and our observational data: (1) the light curves of WISE J0909+0002 present quasi-periodic (sinusoidal) oscillations with the rest-frame period of $\sim$ 660$-$689 day; (2) the structure functions of WISE J0909+0002 do not show a damped random walk (DRW) trend; (3) the mock DRW light curves present periodic-like trend on rare occasions in 10000 simulations; (4) the relativistic boost scenario is favored, since the relation between variability amplitude and power-law slope ratio is consistent with the theoretical prediction of this scenario, and a substantial parameter space exists between the inclination angles and the black hole mass; (5) the circumbinary disk model is difficult to explain the spectral energy distribution of our target; (6) the significant radio flux density of WISE J0909+0002 is not detected from the VLA FIRST Survey, thus the radio jet precession scenario is ruled out. From our results, the Doppler boost scenario is likely as a cause of the periodic variability, consequently the quasi-periodic oscillations in WISE J0909+0002 is possibly interpreted by a supermassive blackhole binary. Additional observations to investigate the continuity of the periodic trend would bring new insights into mechanisms of the quasi-periodic oscillations and/or ELIRGs.

astro-ph.HE↗

arXiv2023

Similarity between compact extremely red objects discovered with JWST in cosmic dawn and blue-excess dust-obscured galaxies known in cosmic noon

Spatially compact objects with extremely red color in the rest-frame optical to near-infrared (0.4--1 ${\rm μm}$) and blue color in the rest-frame ultraviolet (UV; 0.2--0.4 ${\rm μm}$) have been discovered at $5 < z < 9$ using the James Webb Space Telescope (JWST). These extremely red objects (JWST-EROs) exhibit spectral energy distributions (SEDs) that are difficult to explain using a single component of either star-forming galaxies or quasars, leading to two-component models in which the blue UV and extremely red optical are explained using less-dusty and dusty spectra of galaxies or quasars, respectively. Here, we report the remarkable similarity in SEDs between JWST-EROs and blue-excess dust-obscured galaxies (BluDOGs) identified at $2 < z < 3$. BluDOGs are a population of active galactic nuclei (AGNs) with blackhole masses of $\sim10^{8-9}$ M$_\odot$, which are one order of magnitude larger than those in some JWST-EROs. The Eddington ratios of BluDOGs are one or higher, whereas those of JWST-EROs are in the range of 0.1--1. Therefore, JWST-EROs are less massive, less active, and more common counterparts in higher-$z$ of BluDOGs in cosmic noon. Conversely, JWST-EROs have a significantly higher fraction of those with blue-excess than DOGs. We present the average UV spectra of BluDOGs as a comparison to JWST-EROs and discuss a coherent evolutionary scenario for dusty AGN populations.

astro-ph.GA↗

arXiv2023

GREX-PLUS Science Book

GREX-PLUS (Galaxy Reionization EXplorer and PLanetary Universe Spectrometer) is a mission candidate for a JAXA's strategic L-class mission to be launched in the 2030s. Its primary sciences are two-fold: galaxy formation and evolution and planetary system formation and evolution. The GREX-PLUS spacecraft will carry a 1.2 m primary mirror aperture telescope cooled down to 50 K. The two science instruments will be onboard: a wide-field camera in the 2-8 $μ$m wavelength band and a high resolution spectrometer with a wavelength resolution of 30,000 in the 10-18 $μ$m band. The GREX-PLUS wide-field camera aims to detect the first generation of galaxies at redshift $z>15$. The GREX-PLUS high resolution spectrometer aims to identify the location of the water ``snow line'' in proto-planetary disks. Both instruments will provide unique data sets for a broad range of scientific topics including galaxy mass assembly, origin of supermassive blackholes, infrared background radiation, molecular spectroscopy in the interstellar medium, transit spectroscopy for exoplanet atmosphere, planetary atmosphere in the Solar system, and so on.

astro-ph.CO↗

arXiv2022

The physical origin for spatially large scatter of IGM opacity at the end of reionization: the IGM Ly$α$ opacity-galaxy density relation

The large opacity fluctuations in the $z > 5.5$ Ly$α$ forest may indicate inhomogeneous progress of reionization. To explain the observed large scatter of the effective Ly$α$ optical depth ($τ_{\rm eff}$) of the intergalactic medium (IGM), fluctuation of UV background ($Γ$ model) or the IGM gas temperature ($T$ model) have been proposed, which predict opposite correlations between $τ_{\rm eff}$ and galaxy density. In order to address which model can explain the large scatter of $τ_{\rm eff}$, we search for Ly$α$ emitters (LAEs) around two (J1137+3549 and J1602+4228) quasar sightlines with $τ_{\rm eff}\sim3$ and J1630+4012 sightline with $τ_{\rm eff}\sim5.5$. Using a narrowband imaging with Subaru/Hyper Suprime-Cam, we draw LAE density maps to explore their spatial distributions. Overdensities are found within 20 $h^{-1}$Mpc of the quasar sightlines in the low $τ_{\rm eff}$ regions, while a deficit of LAEs is found in the high $τ_{\rm eff}$ region. Although the $τ_{\rm eff}$ of the three quasar sightlines are neither high nor low enough to clearly distinguish the two models, these observed $τ_{\rm eff}$-galaxy density relations all consistently support the $Γ$ model rather than the $T$ model in the three fields, along with the previous studies. The observed overdensities near the low $τ_{\rm eff}$ sightlines may suggest that the relic temperature fluctuation does not affect reionization that much. Otherwise, these overdensities could be attributed to other factors besides the reionization process, such as the nature of LAEs as poor tracers of underlying large-scale structures.

astro-ph.GA↗

arXiv2022

Exploratory Study of Transverse Proximity Effect around BAL Quasars

We aim to find out the reason why there exists an anisotropic HI absorption around quasars; i.e., the environments around quasars are highly biased toward producing strong HI absorption in transverse direction while there exists a significant deficit of HI absorption within a few Mpc of quasars along line-of-sight. The most plausible explanation for this opposite trend is that the transverse direction is shadowed from the quasar UV radiation due to dust torus. However, a critical weakness of this idea is that we have no information on inclination angle of our sightline relative to the torus. In this study, we examine environments of quasars with broad absorption troughs in their spectra (i.e., BAL quasars) because it is widely believed that BAL troughs are observed if the central continuum is viewed from the side through their powerful outflows near the dust torus. With closely separated 12 projected quasar pairs at different redshift with separation angle of $θ$$<$120$^{\prime\prime}$, we examine HI absorption at foreground BAL quasars in spectra of background quasars. We confirm there exist optically thick gas around two of 12 BAL quasars, and that the mean HI absorption strength is EW$_{\rm rest}$$\sim$1A. These are consistent to the past results around non-BAL quasars, although not statistically significant. However, the origins of optically thick HI absorbers around BAL and non-BAL quasars could be different since their column densities are different by $\sim$3 orders of magnitude. The larger sample would be required for narrowing down possible scenarios for the anisotropic HI absorption around quasars.

astro-ph.GA↗

arXiv2021

Multiple MgII Absorption Systems in the Lines of Sight to Quadruply Lensed Quasar H1413+1143

We find multiple Mg II absorption systems at redshift z=1.66, 2.069, and 2.097 in the spatially resolved spectra of the quadruply gravitationally lensed quasar H1413+1143 utilizing the Kyoto tridimensional spectrograph II (Kyoto 3DII) spectrograph on board the Subaru telescope. Here we present the first measurement of differences in Mg II absorption strength of the multiple intervening absorbers, which include ones identified as damped Lyman alpha (DLA) absorption systems. Our detection of the significant Mg II absorptions in the spatially resolved spectra reveals the inhomogeneous chemical enrichment on scales of about 12 kpc within the separation of the four sightlines. For the DLA system at z=1.66, the rest equivalent widths of the Mg II absorption lines between the four spatially resolved lines of sight change by factors of up to about 6, which trace the variations in the H I absorption strength. This suggests that inhomogeneous cold absorbers that give rise to the strong H I/Mg II absorptions dwell on a scale of about 6-12 kpc between the four lines of sight. We also investigate the degree of variation in the equivalent width of the absorption lines between the lines of sight. We find that the systems giving rise to strong absorptions in the spectra of the quadruply lensed quasars tend to have a high degree of variation in absorption strength between the lines of sight toward the lensed quasars.

astro-ph.GA↗

arXiv2021

MCMC-based Voigt Profile fitting to a Mini-BAL System in the Quasar UM675

We introduce a Bayesian approach coupled with a Markov Chain Monte Carlo (MCMC) method and the maximum likelihood statistic for fitting the profiles of narrow absorption lines (NALs) in quasar spectra. This method also incorporates overlap between different absorbers. We illustrate and test this method by fitting models to a "mini-broad" (mini-BAL) and six NAL profiles in four spectra of the quasar UM675 taken over a rest-frame interval of 4.24 years. Our fitting results are consistent with past results for the mini-BAL system in this quasar by Hamann et al. (1997b). We also measure covering factors ($C_{\rm f}$) for two narrow components in the CIV and NV mini-BALs and their overlap covering factor with the broad component. We find that $C_{\rm f}$(NV) is always larger than $C_{\rm f}$(CIV) for the broad component, while the opposite is true for the narrow components in the mini-BAL system. This could be explained if the broad and narrow components originated in gas at different radial distances, but it seems more likely to be due to them produced by gas at the same distance but with different gas densities (i.e., ionization states). The variability detected only in the broad absorption component in the mini-BAL system is probably due to gas motion since both $C_{\rm f}$(CIV) and $C_{\rm f}$(NV) vary. We determine for the first time that multiple absorbing clouds (i.e., a broad and two narrow components) overlap along our line of sight. We conclude that the new method improves fitting results considerably compared to previous methods.

astro-ph.GA↗

arXiv2021

The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems

We present here results from a survey of intervening C IV absorbers at $z < 0.16$ conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems (83%) out of the total sample of 69 have simple kinematics with 1 or 2 C IV components. In the 22 C IV systems with well constrained H I column densities, the temperatures from the $b$-values imply predominantly photoionized plasma ($T\leq 10^5$ K) and non-thermal dynamics. These systems also have solar or higher metallicities. We obtain a C IV line density of $d\mathcal{N}/dX = 5.1\pm 1.0$ for $\log [N(C~IV)~(cm^{-2})]\geq12.9$, and $Ω_{C~IV}=(8.01\pm 1.62) \times 10^{-8}$ for $12.9 \leq \log [N(C~IV)~(cm^{-2})] \leq 15.0$. The C IV bearing diffuse gas in the $z < 0.16$ Universe has a metallicity of $(2.07~{\pm}~0.43)~\times~10^{-3}$ Z$_{\odot}$, an order of magnitude more than the metal abundances in the IGM at high redshifts ($z \gtrsim 5$), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For $z<0.015$ (complete above $L>0.01L^\star$), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C IV ($N>10^{13.5}~cm^{-2}$) with $ρ$ (impact parameter) and $ρ/R_\mathrm{vir}$. However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C IV absorption at $z<0.051$ is not coincident with galaxy over-dense regions complete for $L>0.13L^\star$

astro-ph.GA↗

arXiv2020

Origin of Weak MgII and Higher Ionization Absorption Lines in an Outflow from an Intermediate-Redshift Dwarf Satellite Galaxy

Observations at intermediate redshifts reveal the presence of numerous, compact, weak MgII absorbers with near to super-solar metallicities, often surrounded by more extended regions that produce CIV and/or OVI absorption in the circumgalactic medium at large impact parameters from luminous galaxies. Their origin and nature remains unclear. We hypothesize that undetected, satellite dwarf galaxies are responsible for producing some of these weak MgII absorbers. We test our hypothesis using gas dynamical simulations of galactic outflows from a dwarf satellite galaxy with a halo mass of $5\times10^{9}$ M$_{\odot}$, which could form in a larger $L^{*}$ halo at z=2, to study the gas interaction in the halo. We find that thin, filamentary, weak MgII absorbers are produced in two stages: 1) when shocked core collapse supernova (SNII) enriched gas descending in a galactic fountain gets shock compressed by upward flows driven by subsequent SNIIs and cools (phase 1), and later, 2) during an outflow driven by Type Ia supernovae that shocks and sweeps up pervasive SNII enriched gas, which then cools (phase 2). The width of the filaments and fragments are $\lesssim~100$ pc, and the smallest ones cannot be resolved at 12.8 pc resolution. The MgII absorbers in our simulations are continuously generated for >150 Myr by shocks and cooling, though each cloud survives for only ~60 Myr. Their metallicity is 10-20% solar metallicity and column density is $<10^{12}$ cm$^{-2}$. They are also surrounded by larger (0.5-1 kpc) CIV absorbers that seem to survive longer. In addition, larger-scale (>1 kpc) CIV and OVI clouds are produced in both expanding and shocked SNII enriched gas which is photoionized by the UV metagalactic radiation at intermediate redshift. Our simulation highlights the possibility of dwarf galactic outflows producing highly enriched multiphase gas.

astro-ph.GA↗

arXiv2020

Search for intrinsic NALs in BAL/mini-BAL quasar spectra

Some fraction of narrow absorption lines are physically associated to the quasar/host-galaxy materials (i.e., intrinsic NALs) like those of BALs and mini-BALs. The relation between these three types of absorption lines has not been understood yet, however one interpretation is that these absorption features correspond to different inclination angles. In this study, we search for intrinsic NALs in 11 BAL/mini-BAL quasar spectra retrieved from VLT/UVES public archive, in order to test a possible relation of intrinsic NALs and BALs/mini-BALs in the geometry models. We use partial coverage analysis to separate intrinsic NALs from ones which are associated to cosmologically intervening materials like foreground galaxies and intergalactic medium (i.e., intervening NALs). We identify one reliable and two possible intrinsic NAL systems out of 36 NAL systems in 9 BAL/mini-BAL quasar spectra after removing two quasars without clear BAL features. In spite of a small sample size, we placed a lower limit on the fraction of BAL/mini-BAL quasars that have at least one intrinsic C IV NAL ($\sim33^{+33}_{-18}\%$). This can be interpreted that intrinsic NAL absorbers exist everywhere regardless of inclination angle. We found that one of the intrinsic NAL systems detected in SDSS J121549.80-003432.1 is located at a large radial distance of R > 130 kpc, using a method of photoionization model with ground/excited-state lines. Considering the wide range of intrinsic NAL absorber distribution in inclination angles and radial distances, it suggests that origins and geometry of them are more complicated than we expected.

astro-ph.GA↗

arXiv2020

3D Distribution Map of HI Gas and Galaxies Around an Enormous Ly$α$ Nebula and Three QSOs at $z=2.3$ Revealed by the HI Tomographic Mapping Technique

We present an IGM HI tomography map in a survey volume of $16 \times 19 \times 131 \ h^{-3} {\rm comoving \ Mpc}^{3}$ (cMpc$^3$) centered at MAMMOTH-1 nebula and three neighbouring quasars at $z=2.3$. MAMMOTH-1 nebula is an enormous Ly$α$ nebula (ELAN), hosted by a type-II quasar dubbed MAMMOTH1-QSO, that extends over $1\ h^{-1}$ cMpc with not fully clear physical origin. Here we investigate the HI-gas distribution around MAMMOTH1-QSO with the ELAN and three neighbouring type-I quasars, making the IGM HI tomography map with a spatial resolution of $2.6\ h^{-1}$ cMpc. Our HI tomography map is reconstructed with HI Ly$α$ forest absorption of bright background objects at $z=2.4-2.9$: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate the radial profile of HI flux overdensity for MAMMOTH1-QSO, and find that MAMMOTH1-QSO resides in a volume with significantly weak HI absorption. This suggests that MAMMOTH1-QSO has a proximity zone where quasar illuminates and photo-ionizes the surrounding HI gas and suppresses HI absorption, and that the ELAN is probably a photo-ionized cloud embedded in the cosmic web. The HI radial profile of MAMMOTH1-QSO is very similar to those of three neighbouring type-I quasars at $z=2.3$, which is compatible with the AGN unification model. We compare the distributions of the HI absorption and star-forming galaxies in our survey volume, and identify a spatial offset between density peaks of star-forming galaxies and HI gas. This segregation may suggest anisotropic UV background radiation created by star-forming galaxy density fluctuations.

astro-ph.GA↗