arXiv subjects

Yuichi Matsuda

Publications and source records attributed to Yuichi Matsuda.

At least 19 recordsLinked to original sources

arXiv2026

FINER: development of the wideband millimeter-wave receiver system and preparations for first light on the Large Millimeter Telescope

The recent discovery of an excess of luminous galaxies in the early Universe necessitates sensitive and wideband millimeter spectroscopy to understand their rapid growth. To address this, we present the development of the Far-Infrared Nebular Emission Receiver (FINER) for the Large Millimeter Telescope (LMT). The FINER frontend comprises two receivers covering 120-350 GHz (corresponding to ALMA Bands 4+5 and 6+7). The warm optics are designed to enable simultaneous two-band observations. Combined with the 10.24-GHz-wide digital spectrometer array, the system aims to deliver an instantaneous bandwidth approximately five times wider than current ALMA capabilities. We report that the 210-350 GHz receiver has already achieved commissioning-level performance, with sideband rejection further enhanced by the digital sideband separation technique. With installation expected in 2026, we discuss parallel preparations, including integrated testing and commissioning plans for first-look targets.

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arXiv2026

Compact dusty starbursts at cosmic noon linked to high-energy neutrinos

The origin of high-energy astrophysical neutrinos remains unresolved, and secure electromagnetic counterparts to individual events are rare despite rapid follow-up. Dusty star-forming galaxies (DSFGs) at cosmic noon (z ~ 1-4) are natural cosmic-ray calorimeters, yet observational links between DSFGs and neutrinos have remained elusive. Here we report a compact-core DSFG within an IceCube localization, JCMT0402-0424, a quadruply lensed galaxy at z = 2.988 located inside the 90% containment region of the IceCube event IC 210922A. ALMA imaging and lens modeling resolve a highly magnified, compact starburst with no bright gamma-ray or X-ray counterpart above current sensitivity limits. Considering the positional agreement, the low chance-coincidence probability (less than about 1%) for such an extreme submillimeter source, the absence of equally plausible alternatives in the field, and the compact, gas-rich core revealed by ALMA, JCMT0402-0424 is the most plausible electromagnetic counterpart candidate within the IC 210922A localization. In a population context, compact-core starbursts at cosmic noon can provide a non-negligible population-level contribution to the diffuse high-energy neutrino background, even though the neutrino yield from any single DSFG is modest. This result connects high-energy neutrino production to the peak epoch of cosmic star formation, opening a new avenue to probe galaxy evolution and cosmic-ray acceleration across cosmic time.

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arXiv2025

Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies

We present an analysis of rest-frame optical and far-infrared continuum emission in three luminous submillimeter galaxies (SMGs) at $3.0\lesssim z\lesssim4.5$. The SMGs are spatially resolved down to 400-500 pc (0.05'') resolution by James Webb Space telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. Despite similarities in their observed far-infrared properties (flux density, infrared luminosity, and effective radius), the three SMGs exhibit heterogeneous morphologies both across wavelengths and among the sources themselves. While two of them (AzTEC-4 and AzTEC-8) show a disk-like structure in optical continuum, AzTEC-1 is dominated by highly concentrated component with the Sersic index of $n=5.4$, where its far-infrared continuum emission is clumpy and less concentrated. AzTEC-4, which is confirmed to be at $z=4.198$, shows a two-arm spiral of dust, but not in the stellar distribution. These three SMGs exemplify that multiple physical mechanisms exist in triggering starbursts in luminous SMGs at high redshift: secular instability in gas disks (AzTEC-4) in addition to possible minor mergers (AzTEC-8), and a combination of the efficient gas supply to the central core induced by a gas-rich major merger and the reformation of cold gas disk (AzTEC-1).

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arXiv2025

ALMA Deep Field in SSA22: Reconstructed [CII] Luminosity Function at z = 6

The ADF22 line survey reported detections of two high-$z$ line-emitting source candidates above 6-$\sigma$, both of which were shown to be spurious after follow-up observations. We investigate the detectability of far-infrared emitters in ALMA deep fields using mock observations by injecting artificial line-emitting sources into the visibility planes. We also discuss our investigation, conducted together with the ALMA operations team, of a possible technical problem in the original observations. Finally, we devise a method to estimate the [CII] luminosity function (LF) at $z \sim 6$, including a full analysis of signal contamination and sample completeness. The comparison of pixel distributions between the real and mock datacubes does not show significant differences, confirming that the effect of non-Gaussian noise is negligible for the ADF22 datacube. Using 100 blank mock-mosaic datasets, we show 0.43 $\pm$ 0.67 false detections per datacube with the previous source-finding method. We argue that the underestimation of the contamination rate in the previous work is caused by the smaller number of datacubes, using only 4 real ADF22 datacubes. We compare the results of clump-finding between the time division mode and frequency division mode correlator datacubes and confirm that the velocity widths of the clumps in the TDM case are up to 3 times wider than in the FDM case. The LF estimation using our model shows that a correction for the number count is required, up to one order of magnitude, in the luminosity range of $\geq 5 \times 10^8 L_\odot$. Our reconstruction method for the line LF can be applied to future blind line surveys.

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arXiv2025

ADF22-WEB: ALMA and JWST (sub)kpc-scale views of dusty star-forming galaxies in a $z\approx$3 proto-cluster

We present a morphological analysis of ALMA and JWST NIRCam images of nine dusty star-forming galaxies (DSFGs) at zspec=3.09, all embedded within the cosmic web filaments at the SSA22 proto-cluster core. The ALMA 870um and 1.1mm images are obtained at spatial resolutions ranging from 0.5" to 0.05" (350 pc at z=3.09). The high-resolution images enable us to resolve inner structures traced by dust continuum, identifying compact dusty cores, clumps, and offset ridges within bars. Sersic profile fit was performed for both ALMA 870um and NIRCam F444W images at comparable resolutions (0.15"). The Sersic index measured for 870um, masking bright regions, indicates values close to unity, suggesting that dust emission arises from disks with superimposed compact core components. For the JWST F444W images (restframe 1um), the Sersic indices range between nF444W = 1-3, pointing to the coexistence of bulges and stellar disks in these DSFGs. A comparison of dust mass surface density, nF444W, and F200W-F444W color (restframe 0.5-1um) reveals diversity among the DSFGs, likely reflecting different evolutionary stages including some DSFGs with red cores, indicating ongoing rapid bulge growth phases heavily obscured by dust. The predominantly disk-like morphologies observed in most DSFGs in the proto-cluster core contrast sharply with early-type morphologies that dominate the highest density environment in the local universe. This suggests that we are witnessing the early formation of the morphology-density relation, as massive galaxies undergo rapid growth as late-type galaxies fueled by cosmic web gas filaments.

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arXiv2024

ALMA/SCUBA-2 COSMOS Survey: Properties of X-ray- and SED-selected AGNs in Bright Submillimeter Galaxies

We investigate the properties of active galactic nuclei (AGNs) in the brightest submillimeter galaxies (SMGs) in the COSMOS field. We utilize the bright sample of ALMA/SCUBA-2 COSMOS Survey (AS2COSMOS), which consists of 260 SMGs with $S_{\mathrm{870}\, \mu \mathrm{m}}=0.7\text{--}19.2\,\mathrm{mJy}$ at $z=0\text{--}6$. We perform optical to millimeter spectral energy distribution (SED) modeling for the whole sample. We identify 24 AGN-host galaxies from the SEDs. Supplemented by 23 X-ray detected AGNs (X-ray AGNs), we construct an overall sample of 40 AGN-host galaxies. The X-ray luminosity upper bounds indicate that the X-ray undetected SED-identified AGNs are likely to be nearly Compton thick or have unusually suppressed X-ray emission. From visual classification, we identify $25^{+6}_{-5}$\% of the SMGs without AGNs as major merger candidates. This fraction is almost consistent with the general galaxy population at $z\sim2$, suggesting that major mergers are not necessarily required for the enhanced star formation in SMGs. We also identify $47^{+16}_{-15}$\% of the AGN hosts as major merger candidates, which is about twice as high as that in the SMGs without AGNs. This suggests that major mergers play a key role in triggering AGN activity in bright SMGs.

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arXiv2024

A 100 Mpc$^2$ structure traced by hyperluminous galaxies around a massive $z$ = 2.85 protocluster

We present wide-field mapping at 850 $\mu$m and 450 $\mu$m of the $z$ = 2.85 protocluster in the HS1549$+$19 field using the Submillimetre Common User Bolometer Array 2 (SCUBA-2). Spectroscopic follow-up of 18 bright sources selected at 850 $\mu$m, using the Nothern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter Array (ALMA), confirms the majority lies near $z$ $\sim$ 2.85 and are likely members of the structure. Interpreting the spectroscopic redshifts as distance measurements, we find that the SMGs span 90 Mpc$^2$ in the plane of the sky and demarcate a 4100 Mpc$^3$ "pancake"-shaped structure in three dimensions. We find that the high star-formation rates (SFRs) of these SMGs result in a total SFR of 20,000 M$_\odot$ yr$^{-1}$ only from the brightest galaxies in the protocluster. These rapidly star-forming SMGs can be interpreted as massive galaxies growing rapidly at large cluster-centric distances before collapsing into a virialized structure. We find that the SMGs trace the Lyman-$\alpha$ surface density profile. Comparison with simulations suggests that HS1549$+$19 could be building a structure comparable to the most massive clusters in the present-day Universe.

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arXiv2024

FINER: Far-Infrared Nebular Emission Receiver for the Large Millimeter Telescope

Unveiling the emergence and prevalence of massive/bright galaxies during the epoch of reionization and beyond, within the first 600 million years of the Universe, stands as a pivotal pursuit in astronomy. Remarkable progress has been made by JWST in identifying an immense population of bright galaxies, which hints at exceptionally efficient galaxy assembly processes. However, the underlying physical mechanisms propelling their rapid growth remain unclear. With this in mind, millimeter and submillimeter-wave spectroscopic observations of redshifted far-infrared spectral lines, particularly the [O III] 88 micron and [C II] 158 micron lines, offers a crucial pathway to address this fundamental query. To this end, we develop a dual-polarization sideband-separating superconductor-insulator-superconductor (SIS) mixer receiver, FINER, for the Large Millimeter Telescope (LMT) situated in Mexico. Harnessing advancements from ALMA's wideband sensitivity upgrade (WSU) technology, FINER covers radio frequencies spanning 120-360 GHz, delivering an instantaneous intermediate frequency (IF) of 3-21 GHz per sideband per polarization, which is followed by a set of 10.24 GHz-wide digital spectrometers. At 40% of ALMA's light-collecting area, the LMT's similar atmospheric transmittance and FINER's 5 times wider bandwidth compared to ALMA culminate in an unparalleled spectral scanning capability in the northern hemisphere, paving the way for finer spectral-resolution detection of distant galaxies.

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arXiv2024

The Structure of Massive Star-Forming Galaxies from JWST and ALMA: Dusty, High Redshift Disk Galaxies

We present an analysis of the JWST NIRCam and MIRI morphological properties of 80 massive ($\log_{10}(M_\ast[M_{\odot}])$=11.2$\pm$0.1) dusty star-forming galaxies at $z$$=$2.7$^{+1.2}_{-0.7}$, identified as sub-millimetre galaxies (SMGs) by ALMA, that have been observed as part of the JWST PRIMER project. To compare the structure of these massive, active galaxies to more typical less actively star-forming galaxies, we define two comparison samples. The first of 850 field galaxies matched in specific star-formation rate and redshift and the second of 80 field galaxies matched in stellar mass. We identify 20$\pm$5% of the SMGs as candidate late-stage major mergers, a further 40$\pm$10% as potential minor mergers and 40$\pm$10% which have comparatively undisturbed disk-like morphologies, with no obvious massive neighbours. These rates are comparable to those for the field samples and indicate that the majority of the sub-millimetre-detected galaxies are not late-stage major mergers, but have interaction rates similar to the less-active population at $z$$\sim$2-3. We establish that SMGs have comparable near-infrared sizes to the less active populations, but exhibit lower S\'ersic indices, consistent with bulge-less disks and have more structured morphologies at 2$\mu$m relative to 4$\mu$m. We find evidence for dust reddening as the origin of the morphological differences between the populations, identifying a strong correlation between the F200W$-$F444W pixel colour and the 870$\mu$m surface brightness. We conclude that SMGs and less active galaxies at the same epochs share a common disk-like structure, but the weaker bulge components of the SMGs results in a lower dynamical stability. Consequently, instabilities triggered either secularly or by minor external perturbations result in higher levels of activity (and dust content) in SMGs compared to typical star-forming galaxies. [Abridged]

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arXiv2023

SILVERRUSH. XIII. A Catalog of 20,567 Ly$α$ Emitters at $z=2-7$ Identified in the Full-depth Data of the Subaru/HSC-SSP and CHORUS Surveys

We present 20,567 Ly$α$ emitters (LAEs) at $z=2.2-7.3$ that are photometrically identified by the SILVERRUSH program in a large survey area up to 25 deg$^2$ with deep images of five broadband filters (grizy) and seven narrowband filters targeting Ly$α$ lines at $z=2.2$, $3.3$, $4.9$, $5.7$, $6.6$, $7.0$, and $7.3$ taken by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) and the Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS) survey. We select secure $>5σ$ sources showing narrowband color excesses via Ly$α$ break screening, taking into account the spatial inhomogeneity of limiting magnitudes. After removing spurious sources by careful masking and visual inspection of coadded and multi-epoch images obtained over the 7 yr of the surveys, we construct LAE samples consisting of 6995, 4641, 726, 6124, 2058, 18, and 5 LAEs at $z=2.2$, 3.3, 4.9, 5.7, 6.6, 7.0, and 7.3, respectively, although the $z=7.3$ candidates are tentative. Our LAE catalogs contain 241 spectroscopically confirmed LAEs at the expected redshifts from previous work. We demonstrate that the number counts of our LAEs are consistent with previous studies with similar LAE selection criteria. The LAE catalogs will be made public on our project webpage with detailed descriptions of the content and ancillary information about the masks and limiting magnitudes.

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arXiv2023

The SSA22 HI Tomography Survey (SSA22-HIT). I. Data Set and Compiled Redshift Catalog

We conducted a deep spectroscopic survey, named SSA22-HIT, in the SSA22 field with the DEep Imaging MultiObject Spectrograph (DEIMOS) on the Keck telescope, designed to tomographically map high-z HI gas through analysis of Lya absorption in background galaxies' spectra. In total, 198 galaxies were spectroscopically confirmed at 2.5 < z < 6 with a few low-z exceptions in the 26 x 15 arcmin^2 area, of which 148 were newly determined in this study. Our redshift measurements were merged with previously confirmed redshifts available in the 34 x 27 arcmin^2 area of the SSA22 field. This compiled catalog containing 730 galaxies of various types at z > 2 is useful for various applications, and it is made publicly available. Our SSA22-HIT survey has increased by approximately twice the number of spectroscopic redshifts of sources at z > 3.2 in the observed field. From a comparison with publicly available redshift catalogs, we show that our compiled redshift catalog in the SSA22 field is comparable to those among major extragalactic survey fields in terms of a combination of wide area and high surface number density of objects at z > 2. About 40 % of the spectroscopically confirmed objects in SSA22-HIT show reasonable quality of spectra in the wavelengths shorter than Lya when a sufficient amount of smoothing is adopted. Our data set enables us to make the HI tomographic map at z > 3, which we present in a parallel study.

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arXiv2023

UV & Ly$α$ halos of Ly$α$ emitters across environments at z=2.84

We present UV and Ly$α$ radial surface brightness (SB) profiles of Ly$α$ emitters (LAEs) at $z=2.84$ detected with the Hyper Suprime-Cam (HSC) on the Subaru Telescope. The depth of our data, together with the wide field coverage including a protocluster, enable us to study the dependence of Ly$α$ halos (LAHs) on various galaxy properties, including Mpc-scale environments. UV and Ly$α$ images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of $\sim1\times10^{-20}\mathrm{~erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ in Ly$α$, reaching the expected level of optically thick gas illuminated by the UV background at $z\sim3$. Fitting of the two-component exponential function gives the scale-lengths of $1.56\pm0.01$ and $10.4\pm0.3$ pkpc. Dividing the sample according to their photometric properties, we find that while the dependence of halo scale-length on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters appear to have very large LAHs which could be caused by combined effects of source overlapping and diffuse Ly$α$ emission from cool intergalactic gas permeating the forming protocluster core irradiated by active members. For the first time, we identify ``UV halos'' around bright LAEs which are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude that, while scattered Ly$α$ photons from the host galaxies are dominant, star formation in satellites evidently contributes to LAHs, and that fluorescent Ly$α$ emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs.

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arXiv2023

The JCMT SCUBA-2 Survey of the James Webb Space Telescope North Ecliptic Pole Time-Domain Field

The James Webb Space Telescope Time-Domain Field (JWST-TDF) is an $\sim$14$'$ diameter field near the North Ecliptic Pole that will be targeted by one of the JWST Guaranteed Time Observations programs. Here, we describe our James Clerk Maxwell Telescope SCUBA-2 850 $μ$m imaging of the JWST-TDF and present the submillimeter source catalog and properties. We also present a catalog of radio sources from Karl J. Jansky Very Large Array 3 GHz observations of the field. These observations were obtained to aid JWST's study of the dust-obscured galaxies that contribute significantly to the cosmic star formation at high redshifts. Our deep 850 $μ$m map covers the JWST TDF at a noise level of $σ_{850}$ = 1.0 mJy beam$^{-1}$, detecting 83/31 sources in the main/supplementary signal-to-noise ratio (S/N $>$ 4 / S/N = 3.5 - 4) sample respectively. The 3 GHz observations cover a 24$'$ diameter field with a 1 $σ$ noise of 1$μ$Jy beam$^{-1}$ at a 0$.\!\!^{\prime\prime}$7 FWHM. We identified eighty-five 3 GHz counterparts to sixty-six 850 $μ$m sources and then matched these with multiwavelength data from the optical to the mid-infrared wave bands. We performed spectral energy distribution fitting for 61 submillimeter galaxies (SMGs) matched with optical/near-infrared data, and found that SMGs at S/N $>$ 4 have a median value of $z_{phot} = $2.22 $\pm$ 0.12, star formation rates of 300 $\pm$ 40 M$_{\odot}\,{\rm yr^{-1}}$ (Chabrier initial mass function), and typical cold dust masses of 5.9 $\pm$ 0.7 $ \times$ 10$^{8} $M$_{\odot}$, in line with bright SMGs from other surveys. The large cold dust masses indicate correspondingly large cool gas masses, which we suggest are a key factor necessary to drive the high star formation rates seen in this population

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arXiv2022

An AGN with an ionized gas outflow in a massive quiescent galaxy in a protocluster at $\bf z=3.09$

We report the detection of an ionized gas outflow from an $X$-ray active galactic nucleus (AGN) hosted in a massive quiescent galaxy in a protocluster at $z=3.09$ (J221737.29+001823.4). It is a type-2 QSO with broad ($W_{80}>1000$ km s$^{-1}$) and strong ($\log (L_{\rm [OIII]}$ / erg s$^{-1})\approx43.4$) [O {\footnotesize III}]$λλ$4959,5007 emission lines detected by slit spectroscopy in three-position angles using Multi-Object Infra-Red Camera and Spectrograph (MOIRCS) on the Subaru telescope and the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on the Keck-I telescope. In the all slit directions, [O {\footnotesize III}] emission is extended to $\sim15$ physical kpc and indicates a powerful outflow spreading over the host galaxy. The inferred ionized gas mass outflow rate is $\rm 22\pm3~M_{\odot}~yr^{-1}$. Although it is a radio source, according to the line diagnostics using H$β$, [O {\footnotesize II}], and [O {\footnotesize III}], photoionization by the central QSO is likely the dominant ionization mechanism rather than shocks caused by radio jets. On the other hand, the spectral energy distribution of the host galaxy is well characterized as a quiescent galaxy that has shut down star formation by several hundred Myr ago. Our results suggest a scenario that QSOs are powered after the shut-down of the star formation and help to complete the quenching of massive quiescent galaxies at high redshift.

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arXiv2022

Where Outflows Meet Inflows: Gas Kinematics in SSA22 Lyman-$α$ Blob 2 Decoded by Advanced Radiative Transfer Modelling

We present new spectroscopic observations of Lyman-$α$ (Ly$α$) Blob 2 ($z \sim$ 3.1). We observed extended Ly$α$ emission in three distinct regions, where the highest Ly$α$ surface brightness (SB) center is far away from the known continuum sources. We searched through the MOSFIRE slits that cover the high Ly$α$ SB regions, but were unable to detect any significant nebular emission near the highest SB center. We further mapped the flux ratio of the blue peak to the red peak and found it is anti-correlated with Ly$α$ SB with a power-law index of $\sim$ -0.4. We used radiative transfer models with both multiphase, clumpy and shell geometries and successfully reproduced the diverse Ly$α$ morphologies. We found that most spectra suggest outflow-dominated kinematics, while 4/15 spectra imply inflows. A significant correlation exists between parameter pairs, and the multiphase, clumpy model may alleviate previously reported discrepancies. We also modeled Ly$α$ spectra at different positions simultaneously and found that the variation of the inferred clump outflow velocities can be approximately explained by line-of-sight projection effects. Our results support the `central powering + scattering' scenario, i.e. the Ly$α$ photons are generated by a central powering source and then scatter with outflowing, multiphase HI gas while propagating outwards. The infalling of cool gas near the blob outskirts shapes the observed blue-dominated Ly$α$ profiles, but its energy contribution to the total Ly$α$ luminosity is less than 10%, i.e. minor compared to the photo-ionization by star-forming galaxies and/or AGNs.

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arXiv2022

Detection of nitrogen and oxygen in a galaxy at the end of reionization

We present observations of [NII] 205 $μ$m, [OIII] 88 $μ$m and dust emission in a strongly-lensed, submillimeter galaxy (SMG) at $z=6.0$, G09.83808, with the Atacama Large Millimeter/submillimeter Array (ALMA). Both [NII] and [OIII] line emissions are detected at $>12σ$ in the 0.8$"$-resolution maps. Lens modeling indicates that the spatial distribution of the dust continuum emission is well characterized by a compact disk with an effective radius of 0.64$\pm$0.02 kpc and a high infrared surface brightness of $Σ_\mathrm{IR}=(1.8\pm0.3)\times10^{12}~L_\odot$ kpc$^{-2}$. This result supports that G09.83808 is the progenitors of compact quiescent galaxies at $z\sim4$, where the majority of its stars are expected to be formed through a strong and short burst of star formation. G09.83808 and other lensed SMGs show a decreasing trend of the [NII] line to infrared luminosity ratio with increasing continuum flux density ratio between 63 $μ$m and 158 $μ$m, as seen in local luminous infrared galaxies (LIRGs). The decreasing trend can be reproduced by photoionization models with increasing ionization parameters. Furthermore, by combining the [NII]/[OIII] luminosity ratio with far-infrared continuum flux density ratio in G09.83808, we infer that the gas phase metallicity is already $Z\approx 0.5-0.7~Z_\odot$. G09.83808 is likely one of the earliest galaxies that has been chemically enriched at the end of reionization.

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arXiv2022

FOREVER22: galaxy formation in protocluster regions

We present results from a new cosmological hydrodynamics simulation campaign of protocluster (PC) regions, FOREVER22: FORmation and EVolution of galaxies in Extremely-overdense Regions motivated by SSA22. The simulations cover a wide range of cosmological scales using three different zoom set-ups in a parent volume of $(714.2~\rm cMpc)^{3}$: PCR (Proto-Cluster Region; $V= (28.6~{\rm cMpc})^{3} $, SPH particle mass, $m_{\rm{SPH}} = 4.1 \times 10^{6}~\rm M_{\odot}$ and final redshift, $z_{\rm end}=2.0$), BCG (Brightest proto-Cluster Galaxy; $V \sim (10~{\rm cMpc})^{3} $, $m_{\rm SPH} = 5.0\times10^{5}~\rm M_{\odot}$ and $z_{\rm end}=4.0$ ), and First ( $V \sim (3~{\rm cMpc})^{3} $, $m_{\rm SPH} = 7.9 \times 10^{3}~\rm M_{\odot}$ and $z_{\rm end}=9.5$) runs, that allow to focus on different aspects of galaxy formation. In the PCR runs, we follow 10 PCs, each harbouring 1 - 4 SMBHs with $M_{\rm BH} \ge 10^{9}~\rm M_{\odot}$. One of the PC cores shows a spatially close arrangement of seven starburst galaxies with ${\rm SFR} \gtrsim 100~\rm M_{\odot}~yr^{-1}$ each, that are dust-obscured and would appear as submillimeter galaxies with flux $\gtrsim 1~$ mJy at $1.1~ \rm mm$ in observations. The BCG runs show that the total SFRs of haloes hosting BCGs are affected by AGN feedback, but exceed $1000~\rm M_{\odot}~yr^{-1}$ at $z \lesssim 6$. The First runs resolve mini-haloes hosting population (Pop) III stars and we show that, in PC regions, the dominant stellar population changes from Pop III to Pop II at $z \gtrsim 20$, and the first galaxies with ${\rm SFR} \gtrsim 18~\rm M_{\odot}~yr^{-1}$ form at $z \sim 10$. These can be prime targets for future observations with the James Webb Space Telescope. Our simulations successfully reproduce the global star formation activities in observed PCs and suggest that PCs can kickstart cosmic reionization.

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arXiv2021

A VLA Survey of Late-time Radio Emission from Superluminous Supernovae and the Host Galaxies

We present the results of 3 GHz radio continuum observations of 23 superluminous supernovae (SLSNe) and their host galaxies by using the Karl G. Jansky Very Large Array conducted 5-21 years after the explosions. The sample consists of 15 Type I and 8 Type II SLSNe at z < 0.3, providing one of the largest sample of SLSNe with late-time radio data. We detected radio emission from one SLSN (PTF10hgi) and 5 hosts with a significance of >5$σ$. No time variability is found in late-time radio light curves of the radio-detected sources in a timescale of years except for PTF10hgi, whose variability is reported in a separate study. Comparison of star-formation rates (SFRs) derived from the 3 GHz flux densities with those derived from SED modeling based on UV-NIR data shows that four hosts have an excess of radio SFRs, suggesting obscured star formation. Upper limits for undetected hosts and stacked results show that the majority of the SLSN hosts do not have a significant obscured star formation. By using the 3 GHz upper limits, we constrain the parameters for afterglows arising from interaction between initially off-axis jets and circumstellar medium (CSM). We found that the models with higher energies ($E_{\rm iso} \gtrsim$ several $\times 10^{53}$ erg) and CSM densities ($n \gtrsim 0.01$ cm$^{-3}$) are excluded, but lower energies or CSM densities are not excluded with the current data. We also constrained the models of pulsar wind nebulae powered by a newly born magnetar for a subsample of SLSNe with model predictions in the literature.

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