Abstract
We present ALMA C ii line and far-infrared (FIR) continuum observations of three $z \gt 6$ low-luminosity quasars ($M_{\rm 1450} \gt -25$ mag) discovered by our Subaru Hyper Suprime-Cam ...(HSC) survey. The C ii line was detected in all three targets with luminosities of $(2.4\mbox{--}9.5) \times 10^8\, L_{\odot }$, about one order of magnitude smaller than optically luminous ($M_{\rm 1450} \lesssim -25$ mag) quasars. The FIR continuum luminosities range from $\lt 9 \times 10^{10}\, L_{\odot }$ (3 $\sigma$ limit) to ${\sim } 2 \times 10^{12}\, L_{\odot }$, indicating a wide range in star formation rates in these galaxies. Most of the HSC quasars studied thus far show C ii/ FIR luminosity ratios similar to local star-forming galaxies. Using the C ii-based dynamical mass ($M_{\rm dyn}$) as a surrogate for bulge stellar mass ($M_{\rm\, bulge}$), we find that a significant fraction of low-luminosity quasars are located on or even below the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ relation, particularly at the massive end of the galaxy mass distribution. In contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. Given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. Almost all of the quasars presented in this work are growing their black hole mass at a much higher pace at $z \sim 6$ than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at $z \sim 6$, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.
Abstract
We present deep Keck/MOSFIRE near-infrared spectroscopy of a strong Ly
α
emitting source at
z
= 6.1292, HSC J142331.71−001809.1, which was discovered by the SHELLQS program from imaging data ...of the Subaru Hyper Suprime-Cam (HSC) survey. This source is one of five objects that show narrow (FWHM < 500 km s
−1
) and prominent (
L
Ly
α
> 10
44
erg s
−1
) Ly
α
emission lines at absolute 1450 Å continuum magnitudes of
M
1450
∼ −22 mag. Its rest-frame Ly
α
equivalent width (EW) is 370 ± 30 Å. In the 2 hr Keck/MOSFIRE spectrum in
Y
band, the high-ionization C
iv
λλ
1548,1550 doublet emission line was clearly detected with
FWHM
=
120
−
20
+
20
km s
−1
and a total rest-frame EW of
37
−
5
+
6
Å. We also report the detection of weak continuum emission, and the tentative detection of O
iii
λλ
1661,1666 in the 4 hr
J
-band spectrum. Judging from the UV magnitude, line widths, luminosities, and EWs of Ly
α
and C
iv
, we suggest that this source is a reionization-era analog of classical type-II AGNs, although there is a possibility that it represents a new population of AGN/galaxy composite objects in the early universe. We compare the properties of J1423−0018 to intermediate-redshift type-II AGNs and C
iv
emitters seen in
z
= 6–7 galaxy samples. Further observations of other metal emission lines in the rest-frame UV or optical, along with X-ray follow-up observations of the
z
= 6–7 narrow-line quasars, are needed for more robust diagnostics and to determine their nature.
We explore X-ray evidence for the presence of active galactic nuclei (AGNs) in the two most actively star-forming Green Pea galaxies (GPs), SDSS J0749+3337 and SDSS J0822+2241, which have star ...formation rates (SFRs) of 123 M yr−1 and 78 M yr−1, respectively. The GPs have red mid-infrared (MIR) spectral energy distributions and higher 22 m luminosities than expected from a proxy of the SFR (H luminosity), consistent with hosting AGNs with 2-10 keV luminosities of ∼1044 erg s−1. We thus obtain and analyze the first hard (>10 keV) X-ray data observed with NuSTAR and archival XMM-Newton data below 10 keV. From the NuSTAR 20 ks data, however, we find no significant hard X-ray emission. By contrast, soft X-ray emission with 0.5-8 keV luminosities of 1042 erg s−1 is significantly detected in both targets, which can be explained only by star formation (SF). A possible reason for the lack of clear evidence is that a putative AGN torus absorbs most of the X-ray emission. Applying a smooth-density AGN torus model, we determine minimum hydrogen column densities along the equatorial plane ( ) consistent with the nondetection. The results indicate cm−2 for SDSS J0749+3337 and cm−2 for SDSS J0822+2241. Therefore, the GPs may host such heavily obscured AGNs. Otherwise, no AGN exists and the MIR emission is ascribed to SF. Active SF in low-mass galaxies is indeed suggested to reproduce red MIR colors. This would imply that diagnostics based on MIR photometry data alone may misidentify such galaxies as AGNs.
Karl–Fisher titration is used to estimate water contents in activated carbon and the distribution of impurity-level water in an activated carbon–solvent system. Normalization of the water content of ...activated carbon is attempted using vacuum drying after immersion in water was controlled. Although vacuum drying at 473 K and 24 h can remove large amounts of water, a substantial amount of water remains in the activated carbon. The water release to propylene carbonate is less than that to acetonitrile. The degradation of capacitor cell capacitance for activated carbon with some amount of water differs according to the electrolyte solvent type: acetonitrile promotes greater degradation than propylene carbonate does.
•Water content in activated carbon was estimated.•Karl–Fisher titration was applied for the contacted solvent.•Water release from activated carbon differs by the kind of solvent.•Capacitance degradation is related to the water content in activated carbon.
Abstract
The correlation between the mass of supermassive black holes (SMBHs;
BH
) and their host galaxies (
⋆
) in the reionization epoch provides valuable constraints on their early growth. ...High-redshift quasars typically have an
BH
/
⋆
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
∼ 6 with host properties based on ALMA observations. We find that the observed distribution of quasars in the
BH
–
⋆
plane can be reproduced by assuming that the underlying SMBH population at
z
∼ 6 follows the relationship in the local universe. However, a positive or even a negative evolution in
BH
/
⋆
can also explain the data, depending on whether the intrinsic scatter evolves and on 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
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
BH
/
⋆
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
∼ 6, with active galactic nucleus feedback being a possible driver.
Abstract
We present an imaging molecular line survey in the 3 mm band (85–114 GHz) focused on one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068, based on observations taken ...with the Atacama Large Millimeter/submillimeter Array. Distributions of 23 molecular transitions are obtained in the central ∼3 kpc region, including both the circumnuclear disk (CND) and starburst ring (SBR) with 60 and 350 pc resolution. The column densities and relative abundances of all the detected molecules are estimated under the assumption of local thermodynamic equilibrium in the CND and SBR. Then, we discuss the physical and chemical effects of the AGN on molecular abundance corresponding to the observation scale. We found that H
13
CN, SiO, HCN, and H
13
CO
+
are abundant in the CND relative to the SBR. In contrast,
13
CO is more abundant in the SBR. Based on the calculated column density ratios of
N
(HCN)/
N
(HCO
+
),
N
(HCN)/
N
(CN), and other molecular distributions, we conclude that the enhancement of HCN in the CND may be due to high-temperature environments resulting from strong shocks, which are traced by the SiO emission. Moreover, the abundance of CN in the CND is significantly lower than the expected value of the model calculations in the region affected by strong radiation. The expected strong X-ray irradiation from the AGN has a relatively lower impact on the molecular abundance in the CND than mechanical feedback.
Abstract
We present Karl G. Jansky Very Large Array
K
-band (19 GHz) observations of the redshifted CO(1–0) line emission toward the radio galaxy TN J0924−2201 at
z
= 5.2, which is one of the most ...distant radio galaxies with CO detected. With an angular resolution of ∼2″, the CO(1–0) line emission is resolved into three clumps, within ±500 km s
−1
relative to its redshift, which is determined by Ly
α
. We find that the clumps are located off-center and 12–33 kpc away from the center of the host galaxy, which has counterparts in the Hubble Space Telescope
i
band, Spitzer/IRAC, and the Atacama Large Millimeter/submillimeter Array (ALMA) band 6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate the infrared luminosity
L
IR
and the star formation rate (SFR) of the host galaxy to be (9.3 ± 1.7) × 10
11
L
⊙
and 110 ± 20
M
⊙
yr
−1
, respectively. We also derive the 3
σ
upper limit of
M
H
2
<
1.3
×
10
10
M
⊙
at the host galaxy. The detected CO(1–0) line luminosities of the three clumps,
L
′
CO
(
1
−
0
)
= (3.2–4.7) × 10
10
K km s
−1
pc
2
, indicate the presence of three massive molecular gas reservoirs, with
M
H
2
= (2.5–3.7) × 10
10
M
⊙
, assuming a CO-to-H
2
conversion factor of
α
CO
= 0.8
M
⊙
(
K
km
s
−
1
pc
2
)
−
1
, although the SFR is not elevated due to the nondetection of the ALMA 1.3 mm continuum (SFR < 40
M
⊙
yr
−1
). From the host galaxy, the nearest molecular gas clump, labeled “clump A,” is apparently in alignment with the radio jet axis, showing radio–CO alignment. The origins of these three clumps around TN J0924–2201 can possibly be interpreted as outflows, mergers, or jet-induced metal enrichment.
We present a dynamical mass measurement of the supermassive black hole (SMBH) in the nearby double-barred spiral galaxy NGC 3504 as part of the Measuring Black Holes in below Milky Way (M ) Mass ...Galaxies Project. Our analysis is based on Atacama Large Millimeter/submillimeter Array cycle 5 observations of the emission line. These observations probe NGC 3504's circumnuclear gas disk (CND). Our dynamical model of the CND simultaneously constrains a black hole (BH) mass of M , which is consistent with the empirical BH-galaxy scaling relations and a mass-to-light ratio in the H band of 0.44 0.12 (M / ). This measurement also relies on our new estimation of the distance to the galaxy of 32.4 2.1 Mpc using the surface brightness fluctuation method, which is much further than the existing distance estimates. Additionally, our observations detect a central deficit in the integrated intensity map with a diameter of 6.3 pc at the putative position of the SMBH. However, we find that a dense gas tracer CS(5 − 4) peaks at the galaxy center, filling in the 12CO(2 − 1)-attenuated hole. Holes like this one are observed in other galaxies, and our observations suggest these may be caused by changing excitation conditions rather than a true absence of molecular gas around the nucleus.
We present measurements of the size of the quasar proximity zone (Rp) for 11 low-luminosity ( ) quasars at z ∼ 6, discovered by the Subaru High-z Exploration of Low-Luminosity Quasars project. Our ...faint quasar sample expands the Rp measurement down to mag, where more common quasar populations dominate at the epoch. We restrict the sample to quasars whose systemic redshifts have been precisely measured by C ii 158 m or Mg ii λ2798 emission lines. We also update the Rp measurements for 26 luminous quasars presented in Eilers et al. by using the latest systemic redshift results. The luminosity dependence on Rp is found to be consistent with the theoretical prediction assuming a highly ionized intergalactic medium. We find a shallow redshift evolution of the luminosity-corrected Rp, ( ) over . This trend is steeper than that of Eilers et al., but significantly shallower than those of the earlier studies. Our results suggest that Rp,corr is insensitive to the neutral fraction of the universe at z ∼ 6. Four quasars show exceptionally small ( proper Mpc), which could be the result of their young age (<104 yr) in the reionization epoch, though statistics on this are still scarce.
Abstract
We present new Atacama Large Millimeter/submillimeter Array (ALMA) results obtained from spatially resolved CO
J
= 2–1 line (0.″4 resolution) and 870
μ
m continuum (0.″2 resolution) ...observations of cluster galaxies in XMMXCS J2215.9-1738 at
z
= 1.46. Our sample comprises 17 galaxies within ∼0.5 Mpc (0.6
R
200
) of the cluster center, all of which have previously been detected in the CO
J
= 2–1 line at a lower resolution. The effective radii of both the CO
J
= 2–1 line and 870
μ
m dust continuum emissions are robustly measured for nine galaxies by modeling the visibilities. We find that the CO
J
= 2–1 line emission in all of the nine galaxies is more extended than the dust continuum emission by a factor of 2.8 ± 1.4. We investigate the spatially resolved Kennicutt–Schmidt (KS) relation in two regions within the interstellar medium of the galaxies. The relation for our sample reveals that the central region (0 <
r
<
R
e
,870
μ
m
) of galaxies tends to have a shorter gas depletion timescale, i.e., a higher star formation efficiency, compared to the extended region (
R
e
,870
μ
m
<
r
<
R
e
,CO
). Overall, our result suggests that star formation activities are concentrated inside the extended gas reservoir, possibly resulting in the formation of a bulge structure. We find consistency between the ALMA 870
μ
m radii of star-forming members and the Hubble Space Telescope/1.6
μ
m radii of passive members in a mass–size distribution, which suggests a transition from star-forming to passive members within ∼0.5 Gyr. In addition, no clear differences in the KS relation nor in the sizes are found between galaxies with and without a close companion.
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