We present deep near-infrared spectroscopy of six quasars at 6.1 ≤ z ≤ 6.7 with Very Large Telescope/X-Shooter and Gemini-N/GNIRS. Our objects, originally discovered through a wide-field optical ...survey with the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP), have the lowest luminosities (−25.5 mag ≤ M1450 ≤ −23.1 mag) of the z > 5.8 quasars with measured black hole (BH) masses. From single-epoch mass measurements based on Mg ii λ2798, we find a wide range in BH masses, from MBH = 107.6 to 109.3 M . The Eddington ratios Lbol/LEdd range from 0.16 to 1.1, but the majority of the HSC quasars are powered by MBH ∼ 109 M supermassive black holes (SMBHs) accreting at sub-Eddington rates. The Eddington ratio distribution of the HSC quasars is inclined to lower accretion rates than those of Willott et al., who measured the BH masses for similarly faint z ∼ 6 quasars. This suggests that the global Eddington ratio distribution is wider than has previously been thought. The presence of MBH ∼ 109 M SMBHs at z ∼ 6 cannot be explained with constant sub-Eddington accretion from stellar remnant seed BHs. Therefore, we may be witnessing the first buildup of the most massive BHs in the first billion years of the universe, the accretion activity of which is transforming from active growth to a quiescent phase. Measurements of a larger complete sample of z 6 low-luminosity quasars, as well as deeper observations with future facilities, will enable us to better understand the early SMBH growth in the reionization epoch.
Abstract
Supermassive black holes (SMBHs) are thought to originate from early universe seed black holes of mass
M
BH
∼ 10
2
–10
5
M
⊙
and grown through cosmic time. Such seeds could be powering the ...active galactic nuclei (AGN) found in today’s dwarf galaxies. However, probing a connection between the early seeds and local SMBHs has not yet been observationally possible. Massive black holes hosted in dwarf galaxies at intermediate redshifts, on the other hand, may represent the evolved counterparts of the seeds formed at very early times. We present a sample of seven broad-line AGN in dwarf galaxies with a spectroscopic redshift ranging from
z
= 0.35 to
z
= 0.93. The sources are drawn from the VIPERS survey as having an Large Magellanic Cloud (LMC) like stellar mass (
M
∗
) derived from spectral energy distribution fitting, and they are all star-forming galaxies. Six of these sources are also X-ray AGN. The AGN are powered by SMBHs of >10
7
M
⊙
, more massive than expected from the
M
BH
–
M
∗
scaling relation of AGN. Based on semianalytical simulations, we find that these objects are likely overmassive with respect to their hosts since early times (
z
> 4), independently of whether they formed as heavy (∼10
5
M
⊙
) or light (∼10
2
M
⊙
) seed black holes. In our simulations, these objects tend to grow faster than their host galaxies, contradicting models of synchronized growth. The host galaxies are found to possibly evolve into massive systems by
z
∼ 0, indicating that local SMBHs in massive galaxies could originate in dwarf galaxies hosting seed black holes at higher
z
.
Abstract We report for the first time a sample of 12 supermassive black holes (SMBHs) hosted by low-mass galaxies at cosmic noon, i.e., in a redshift range consistent with the peak of star formation ...history: z ∼ 1–3. These black holes are 2 orders of magnitude too massive for the stellar content of their hosts when compared with the local relation for active galaxies. These overmassive systems at cosmic noon share similar properties with the high- z sources found ubiquitously in recent James Webb Space Telescope (JWST) surveys (same range of black-hole-to-stellar-mass ratio, bolometric luminosity, and Eddington ratio). We argue that black hole feedback processes, for which there is possible evidence in five of the sources, and the differing environments in galactic nuclei at these respective epochs play a key role in these overmassive systems. These findings contribute to our understanding of the growth and coevolution of SMBHs and their host galaxies across cosmic time, offering a link between the early Universe ( z > 4) observed by JWST and observations of the present-day Universe ( z ≲ 1).
We investigate the multi-wavelength properties of host galaxies of 3701 X-ray-selected active galactic nuclei (AGNs) out to z ∼ 5 in the Chandra-COSMOS Legacy Survey. Thanks to the extensive ...multi-wavelength photometry available in the COSMOS field, we derive AGN luminosities, host stellar masses, and star formation rates (SFRs) via a multi-component SED fitting technique. Type 1 and Type 2 AGNs follow the same intrinsic L2-10 keV-L6 m relation, suggesting that mid-infrared emission is a reasonably good measure of the AGN accretion power regardless of obscuration. We find that there is a strong increase in Type 1 AGN fraction toward higher AGN luminosity, possibly due to the fact that Type 1 AGNs tend to be hosted by more massive galaxies. The AGN luminosity and SFR are consistent with an increase toward high stellar mass, while the Mstellar dependence is weaker toward the high-mass end, which could be interpreted as a consequence of quenching both star formation and AGN activity in massive galaxies. AGN host galaxies tend to have SFRs that are consistent with normal star-forming galaxies, independent of AGN luminosities. We confirm that black hole accretion rate and SFR are correlated up to z ∼ 5, when forming stars. The majority (∼73%) of our AGN sample are faint in the far-infrared, implying that the moderate-luminosity AGNs seem to be still active after the star formation is suppressed. It is not certain whether AGN activity plays a role in quenching the star formation. We conclude that both AGN activity and star formation might be more fundamentally related to host stellar mass.
Abstract
We present Atacama Large Millimeter/submillimeter Array C
ii
158
μ
m line and underlying far-infrared (FIR) continuum emission observations (0.″70 × 0.″56 resolution) toward HSC ...J124353.93+010038.5 (J1243+0100) at
z
= 7.07, the only low-luminosity (
M
1450
> −25 mag) quasar currently known at
z
> 7. The FIR continuum is bright (1.52 mJy) and resolved with a total luminosity of
L
FIR
= 3.5 × 10
12
L
⊙
. The spatially extended component is responsible for ∼40% of the emission. The area-integrated C
ii
spectrum shows a broad wing (FWHM = 997 km s
−1
,
L
C
ii
= 1.2 × 10
9
L
⊙
), as well as a bright core (FWHM = 235 km s
−1
,
L
C
ii
= 1.9 × 10
9
L
⊙
). This wing is the first detection of a galactic-scale quasar-driven outflow (atomic outflow rate >447
M
⊙
yr
−1
) at
z
> 7. The estimated large mass-loading factor of the total outflow (e.g., ≳9 relative to the C
ii
-based star formation rate) suggests that this outflow will soon quench the star formation of the host. The core gas dynamics are governed by rotation, with a rotation curve suggestive of a compact bulge (∼3.3 × 10
10
M
⊙
), although it is not yet spatially resolved. Finally, we found that J1243+0100 has a black hole mass–to–dynamical mass (and –to–bulge mass) ratio of ∼0.4% (∼1%), consistent with the local value within the uncertainties. Our results therefore suggest that the black hole–host coevolution relation is already in place at
z
∼ 7 for this object.
Cardiovascular complications are the major causes of death in patients with diabetes mellitus. Several studies have demonstrated that endothelial progenitor cells (EPCs), adult stem cells ...contributing to the regeneration of vascular endothelium, are dysfunctional under diabetic condition resulting in impaired peripheral circulation and delayed wound healing. In this study, we investigated the cellular alteration of EPCs under high glucose condition, to elucidate the mechanisms underlying diabetes-associated EPC dysfunction. EPCs were isolated from bone marrow and cultured in normal glucose (5.5 mM)- or high glucose (HG; 30 mM)-containing medium. High glucose treated-EPCs showed decreased ability to form tubule-like networks in Matrigel compared to EPCs under normal glucose, which matched well to the clinical observation of diabetic EPC dysfunction. Conversion of LC3-I to LC3-II was increased in EPCs under HG condition, showing that HG induced autophagy in EPCs. Flow cytometric analysis revealed generation of oxidative stress and disruption of mitochondrial permeability in HG exposed EPCs. Increased mitochondrial oxidative stress was also observed by mitochondria-specific superoxide indicator, MitoSOXTM. Taken together, we demonstrated that autophagy and mitochondrial impairment were induced in EPCs under high glucose condition, giving a new insight into the mechanism underlying dysfunction of diabetic EPCs. We hope that our finding can contribute to the development of a new treatment option for cardiovascular complications in diabetic patients.
The unique combination of superb spatial resolution, wide-area coverage, and deep depth of the optical imaging from the Hyper Suprime-Cam (HSC) Subaru Strategic Program is utilized to search for dual ...quasar candidates. Using an automated image analysis routine on 34,476 known Sloan Digital Sky Survey quasars, we identify those with two (or more) distinct optical point sources in HSC images covering 796 deg2. We find 421 candidates out to a redshift of 4.5 of which one hundred or so are more likely after filtering out contaminating stars. Angular separations of 0 6-4 0 correspond to projected separations of 3-30 kpc, a range relatively unexplored for population studies of luminous dual quasars. Using Keck I/Low Resolution Imaging Spectrometer and Gemini-N/Near-Infrared Integral Field Spectrometer, we spectroscopically confirm three dual quasar systems at z < 1, two of which are previously unknown out of eight observed, based on the presence of characteristic broad emission lines in each component, while highlighting that the continuum of one object in one of the pairs is reddened. In all cases, the O iiiλ5007 emission lines have mild velocity offsets, thus the joint O iii line profile is not double-peaked. We find a dual quasar fraction of 0.26 0.18% and no evidence for evolution. A comparison with the Horizon-AGN simulation seems to support the case of no evolution in the dual quasar fraction when broadly matching the quasar selection. These results may indicate a scenario in which the frequency of the simultaneous triggering of luminous quasars is not as sensitive as expected to the cosmic evolution of the merger rate or gas content of galaxies.
Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation ...emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet established. We present spectroscopic observations of a galaxy at redshift z = 3.328, which hosts an actively accreting, extremely massive BH, in its final stages of growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy, suggesting that it has grown much more efficiently than the host, contrary to models of synchronized coevolution. The host galaxy is forming stars at an intense rate, despite the presence of a SMBH-driven gas outflow.
Abstract
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, including three previously published, we find that the black holes in these systems have black hole masses (
M
BH
∼ 10
8−9
M
⊙
), bolometric luminosities (log
L
bol
∼ 44.5–47.5 erg s
–1
) and Eddington ratios (0.01–0.3) similar to single SDSS quasars. 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 by mergers prior to the final coalescence of the two SMBHs, resulting in early mass growth of the black holes relative to their host galaxies.
Abstract
We present Atacama Large Millimeter/submillimeter Array C
ii
158
μ
m line and far-infrared (FIR) continuum emission observations toward HSC J120505.09−000027.9 (J1205−0000) at
z
= 6.72 with ...a beam size of ∼0.″8 × 0.″5 (or 4.1 kpc × 2.6 kpc), the most distant red quasar known to date. Red quasars are modestly reddened by dust and are thought to be in rapid transition from an obscured starburst to an unobscured normal quasar, driven by powerful active galactic nucleus (AGN) feedback that blows out a cocoon of interstellar medium. The FIR continuum of J1205−0000 is bright, with an estimated luminosity of
L
FIR
∼ 3 × 10
12
L
⊙
. The C
ii
line emission is extended on scales of
r
∼ 5 kpc, greater than that of the FIR continuum. The line profiles at the extended regions are complex and broad (FWHM ∼ 630–780 km s
−1
). Although it is not practical to identify the nature of this extended structure, possible explanations include (i) companion/merging galaxies and (ii) massive AGN-driven outflows. For the case of (i), the companions are modestly star-forming (∼10
M
⊙
yr
−1
) but are not detected by our Subaru optical observations (
y
AB,5
σ
= 24.4 mag). For the case of (ii), our lower limit to the cold neutral outflow rate is ∼100
M
⊙
yr
−1
. The outflow kinetic energy and momentum are both much lower than predicted in energy-conserving wind models, suggesting that the AGN feedback in this quasar is not capable of completely suppressing its star formation.
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