arXiv subjects

Tomoko Suzuki

Publications and source records attributed to Tomoko Suzuki.

4 recordsLinked to original sources

arXiv2024

Rich and diverse molecular gas environments of closely-separated dual quasars viewed by ALMA

We present a study of the molecular gas in five closely-spaced ($R_{\perp}<20$ kpc) dual quasars ($L_{\rm bol}\gtrsim10^{44}~\mathrm{erg~s}^{-1}$) at redshifts $0.4<z<0.8$ with the Atacama Large Millimeter/submillimeter Array. The dual quasar phase represents a distinctive stage during the interaction between two galaxies for investigating quasar fueling and feedback effects on the gas reservoir. The dual quasars were selected from the Sloan Digital Sky Survey and Subaru/Hyper Suprime-Cam Subaru Strategic Program, with confirmatory spectroscopic validation. Based on the detection of the CO J=2--1 emission line with Band 4, we derived key properties including CO luminosities, line widths, and molecular gas masses for these systems. Among the ten quasars of the five pairs, eight have line detections exceeding $5σ$. The detected sources prominently harbor substantial molecular gas reservoirs, with molecular gas masses ($M_{\text{molgas}}$) between $10^{9.6-10.5}~\mathrm{M_{\odot}}$, and molecular gas-to-stellar mass ratios ($μ_{\text{molgas}}$) spanning $18-97\%$. The overall $μ_{\text{molgas}}$ of these dual quasars agrees with that of inactive star-forming main-sequence galaxies at comparable redshifts, indicating no clear evidence of quenching. However, intriguing features in each individual system show possible evidence of AGN feedback, matter transfer, and compaction processes.

astro-ph.GA↗

arXiv2019

Environmental impacts on molecular gas in protocluster galaxies at z~2

We present the results from ALMA CO(3-2) observations of 66 Halpha-selected galaxies in three protoclusters around radio galaxies, PKS1138-262 (z=2.16) and USS1558-003 (z=2.53), and 4C23.56 (z=2.49). The pointing areas have an overdensity of ~100 compared to a mean surface number density of galaxies in field environments. We detect CO emission line in 16 star-forming galaxies, including previously published six galaxies, to measure the molecular gas mass. In the stellar mass range of 10.5 11.0 are comparable in mass to the scaling relation, or smaller. Our results suggest that the environmental effects on gas properties are mass-dependent: in high-density environments, gas accretion through cosmic filaments is accelerated in less massive galaxies while this is suppressed in the most massive system.

astro-ph.GA↗

arXiv2018

Alma Twenty-six Arcmin^2 Survey Of Goods-s At One-millimeter (asagao): Source Catalog And Number Counts

We present the survey design, data reduction, construction of images, and source catalog of the Atacama Large Millimeter/submillimeter Array (ALMA) twenty-six arcmin^2 survey of GOODS-S at one-millimeter (ASAGAO). ASAGAO is a deep (1sigma ~ 61 uJy/beam for a 250 klambda-tapered map with a synthesized beam size of 0.51" x 0.45") and wide area (26 arcmin^2) survey on a contiguous field at 1.2 mm. By combining with ALMA archival data in the GOODS-South field, we obtained a deeper map in the same region (1sigma ~ 30 uJy/beam for a deep region with a 250 klambda-taper, and a synthesized beam size of 0.59" x 0.53"), providing the largest sample of sources (25 sources at >=5.0sigma, 45 sources at >=4.5sigma) among ALMA blank-field surveys to date. The number counts shows that 52(+11 -8)% of the extragalactic background light at 1.2 mm is resolved into discrete sources at S1.2m > 135 uJy. We create infrared (IR) luminosity functions (LFs) in the redshift range of z = 1-3 from the ASAGAO sources with KS-band counterparts, and constrain the faintest luminosity of the LF at 2.0 < z < 3.0. The LFs are consistent with previous results based on other ALMA and SCUBA-2 observations, which suggest a positive luminosity evolution and negative density evolution with increasing redshift. We find that obscured star-formation of sources with IR luminosities of log(L(IR)/Lsun)} ~> 11.8 account for ~~60%-90% of the z ~ 2 cosmic star-formation rate density.

astro-ph.GA↗

arXiv2017

The nature of H$α$-selected galaxies along the large-scale structure at z=0.4 revealed by Subaru Hyper Suprime-Cam survey

We present the environmental dependence of colour, stellar mass, and star formation (SF) activity in H-alpha-selected galaxies along the large-scale structure at z=0.4 hosting twin clusters in DEEP2-3 field, discovered by Subaru Strategic Programme of Hyper Suprime-Cam (HSC SSP). By combining photo-z selected galaxies and H-alpha emitters selected with broad-band and narrow-band (NB) data of the recent data release of HSC SSP (DR1), we confirm that galaxies in higher-density environments or galaxies in the cluster central regions show redder colours. We find that there still remains a possible colour-density and colour-radius correlation even if we restrict the sample to H-alpha-selected galaxies, likely due to the presence of massive H-alpha emitters in denser regions. We also find a hint of increased star formation rates (SFR) amongst H-alpha emitters towards the highest-density environment, again primarily driven by the excess of red/massive H-alpha emitters in high-density environment, while their specific SFR does not significantly change with environment. This work demonstrates the power of the HSC SSP NB data to study SF galaxies across environment in the distant universe.

astro-ph.GA↗