Search

We investigate the origin of star formation activity in early-type galaxies with current star formation using spatially resolved spectroscopic data from the Mapping Nearby Galaxies at APO (MaNGA) in the Sloan Digital Sky Survey (SDSS). We first identify star-forming early-type galaxies from the SDSS sample, which are morphologically early-type but show current star formation activity in their optical spectra. We then construct comparison samples with different combinations of star formation activity and morphology, which include star-forming late-type galaxies, quiescent early-type galaxies and quiescent late-type galaxies. Our analysis of the optical spectra reveals that the star-forming early-type galaxies have two distinctive episodes of star formation, which is similar to late-type galaxies but different from quiescent early-type galaxies with a single star formation episode. Star-forming early-type galaxies have properties in common with star-forming late-type galaxies, which include stellar population, gas and dust content, mass and environment. However, the physical properties of star-forming early-type galaxies derived from spatially resolved spectroscopy differ from those of star-forming late-type galaxies in the sense that the gas in star-forming early-type galaxies is more concentrated than their stars, and is often kinematically misaligned with stars. The age gradient of star-forming early-type galaxies also differs from those of star-forming late-type galaxies. Our findings suggest that the current star formation in star-forming early-type galaxies has an external origin including galaxy mergers or accretion gas from the cosmic web., 19 pages, 12 figures

Full list of authors: Lan, Ting-Wen; Tojeiro, R.; Armengaud, E.; Prochaska, J. Xavier; Davis, T. M.; Alexander, David M.; Raichoor, A.; Zhou, Rongpu; Yeche, Christophe; Balland, C.; BenZvi, S.; Berti, A.; Canning, R.; Carr, A.; Chittenden, H.; Cole, S.; Cousinou, M. -c.; Dawson, K.; Dey, Biprateep; Douglass, K.; Edge, A.; Escoffier, S.; Glanville, A.; Gontcho, S. Gontcho; Guy, J.; Hahn, C.; Howlett, C.; Hwang, Ho Seong; Jiang, L.; Kovacs, A.; Mezcua, M.; Moore, S.; Nadathur, S.; Oh, M.; Parkinson, D.; Rocher, A.; Ross, A. J.; Ruhlmann-Kleider, V.; Sabiu, C. G.; Said, K.; Saulder, C.; Sierra-Porta, D.; Weiner, B.; Yu, J.; Zarrouk, P.; Zhang, Y.; Zou, H.; Ahlen, S.; Bailey, S.; Brooks, D.; Cooper, A. P.; de la Macorra, A.; Dey, A.; Dhungana, G.; Doel, P.; Eftekharzadeh, S.; Fanning, K.; Font-Ribera, A.; Garrison, L.; Gaztanaga, E.; Kehoe, R.; Kisner, T.; Kremin, A.; Landriau, M.; Le Guillou, L.; Levi, Michael E.; Magneville, C.; Meisner, Aaron M.; Miquel, R.; Moustakas, J.; Myers, Adam D.; Newman, Jeffrey A.; Nie, J. D.; Palanque-Delabrouille, N.; Percival, W. J.; Poppett, C.; Prada, F.; Schubnell, M.; Tarle, Gregory; Weaver, B. A.; Zhang, K.; Zhou, Zhimin.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements of galaxies to validate the final survey design and target selections. To assist in these tasks, we visually inspect DESI spectra of approximately 2500 bright galaxies, 3500 luminous red galaxies (LRGs), and 10,000 emission-line galaxies (ELGs) to obtain robust redshift identifications. We then utilize the visually inspected redshift information to characterize the performance of the DESI operation. Based on the visual inspection (VI) catalogs, our results show that the final survey design yields samples of bright galaxies, LRGs, and ELGs with purity greater than 99%. Moreover, we demonstrate that the precision of the redshift measurements is approximately 10 km s−1 for bright galaxies and ELGs and approximately 40 km s−1 for LRGs. The average redshift accuracy is within 10 km s−1 for the three types of galaxies. The VI process also helps improve the quality of the DESI data by identifying spurious spectral features introduced by the pipeline. Finally, we show examples of unexpected real astronomical objects, such as Lyα emitters and strong lensing candidates, identified by VI. These results demonstrate the importance and utility of visually inspecting data from incoming and upcoming surveys, especially during their early operation phases. © 2023. The Author(s). Published by the American Astronomical Society., W.L. is supported by the Ministry of Science and Technology (MOST 111-2112-M-002-015-MY3), the Ministry of Education, Taiwan (MOE Yushan Young Scholar grant Nos. NTU-110VV007 and NTU-110VV007-2), National Taiwan University research grant Nos. NTU-CC-111L894806, NTU-111L7318, and NTU-112L7302 and NSF grant No. AST-1911140. D.M.A. acknowledges the Science Technology and Facilities Council (STFC) for support through grant No. ST/T000244/1. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

How does the environment affect active galactic nucleus (AGN) activity? We investigated this question in an extinction-free way, by selecting 1120 infrared galaxies in the $AKARI$ North Ecliptic Pole Wide field at redshift $z$ $\leq$ 1.2. A unique feature of the $AKARI$ satellite is its continuous 9-band infrared (IR) filter coverage, providing us with an unprecedentedly large sample of IR spectral energy distributions (SEDs) of galaxies. By taking advantage of this, for the first time, we explored the AGN activity derived from SED modelling as a function of redshift, luminosity, and environment. We quantified AGN activity in two ways: AGN contribution fraction (ratio of AGN luminosity to the total IR luminosity), and AGN number fraction (ratio of number of AGNs to the total galaxy sample). We found that galaxy environment (normalised local density) does not greatly affect either definitions of AGN activity of our IRG/LIRG samples (log ${\rm L}_{\rm TIR}$ $\leq$ 12). However, we found a different behavior for ULIRGs (log ${\rm L}_{\rm TIR}$ $>$ 12). At our highest redshift bin (0.7 $\lesssim$ z $\lesssim$ 1.2), AGN activity increases with denser environments, but at the intermediate redshift bin (0.3 $\lesssim$ z $\lesssim$ 0.7), the opposite is observed. These results may hint at a different physical mechanism for ULIRGs. The trends are not statistically significant (p $\geq$ 0.060 at the intermediate redshift bin, and p $\geq$ 0.139 at the highest redshift bin). Possible different behavior of ULIRGs is a key direction to explore further with future space missions (e.g., $JWST$, $Euclid$, $SPHEREx$)., Accepted for publication in MNRAS. A summary video is available at https://www.youtube.com/watch?v=7Y_a0kJkLI4&ab_channel=NthuCosmology

Galaxy clusters provide an excellent probe in various research fields in astrophysics and cosmology. However, the number of galaxy clusters detected so far in the $AKARI$ North Ecliptic Pole (NEP) field is limited. In this work, we provide galaxy cluster candidates in the $AKARI$ NEP field with the minimum requisites based only on coordinates and photometric redshift (photo-$z$) of galaxies. We used galaxies detected in 5 optical bands ($g$, $r$, $i$, $z$, and $Y$) by the Subaru Hyper Suprime-Cam (HSC), assisted with $u$-band from Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam, and IRAC1 and IRAC2 bands from the $Spitzer$ space telescope for photo-$z$ estimation. We calculated the local density around every galaxy using the 10$^{th}$-nearest neighbourhood. Cluster candidates were determined by applying the friends-of-friends algorithm to over-densities. 88 cluster candidates containing 4390 member galaxies below redshift 1.1 in 5.4 deg$^2$ have been detected. The reliability of our method was examined through false detection tests, redshift uncertainty tests, and applications on the COSMOS data, giving false detection rates of 0.01 to 0.05 and recovery rate of 0.9 at high richness. 3 X-ray clusters previously observed by $ROSAT$ and $Chandra$ were recovered. The cluster galaxies show higher stellar mass and lower star formation rate (SFR) compared to the field galaxies in two-sample Z-tests. These cluster candidates are useful for environmental studies of galaxy evolution and future astronomical surveys in the NEP, where $AKARI$ has performed unique 9-band mid-infrared photometry for tens of thousands of galaxies., Comment: 19 pages, 16 figures, has been accepted for publication in MNRAS

We present a study of the stellar populations of globular clusters (GCs) in the Virgo Cluster core with a homogeneous spectroscopic catalog of 692 GCs within a major axis distance $R_{\rm maj} = $ 840 kpc from M87. We investigate radial and azimuthal variations in the mean age, total metallicity, [Fe/H], and $\alpha$-element abundance, of blue (metal-poor) and red (metal-rich) GCs using their co-added spectra. We find that the blue GCs have a steep radial gradient in [Z/H] within $R_{\rm maj} =$ 165 kpc, with roughly equal contributions from [Fe/H] and [$\alpha$/Fe], and flat gradients beyond. By contrast, the red GCs show a much shallower gradient in [Z/H], which is entirely driven by [Fe/H]. We use GC-tagged Illustris simulations to demonstrate an accretion scenario where more massive satellites (with more metal- and $\alpha$-rich GCs) sink further into the central galaxy than less massive ones, and where the gradient flattening occurs because of the low GC occupation fraction of low-mass dwarfs disrupted at larger distances. The dense environment around M87 may also cause the steep [$\alpha$/Fe] gradient of the blue GCs, mirroring what is seen in the dwarf galaxy population. The progenitors of red GCs have a narrower mass range than those of blue GCs, which makes their gradients shallower. We also explore spatial inhomogeneity in GC abundances, finding that the red GCs to the northwest of M87 are slightly more metal-rich. Future observations of GC stellar population gradients will be useful diagnostics of halo merger histories., Comment: 22 pages, 8 figures, 4 tables, accepted for publication in ApJ

To understand the cosmic accretion history of supermassive black holes, separating the radiation from active galactic nuclei (AGNs) and star-forming galaxies (SFGs) is critical. However, a reliable solution on photometrically recognising AGNs still remains unsolved. In this work, we present a novel AGN recognition method based on Deep Neural Network (Neural Net; NN). The main goals of this work are (i) to test if the AGN recognition problem in the North Ecliptic Pole Wide (NEPW) field could be solved by NN; (ii) to shows that NN exhibits an improvement in the performance compared with the traditional, standard spectral energy distribution (SED) fitting method in our testing samples; and (iii) to publicly release a reliable AGN/SFG catalogue to the astronomical community using the best available NEPW data, and propose a better method that helps future researchers plan an advanced NEPW database. Finally, according to our experimental result, the NN recognition accuracy is around 80.29% - 85.15%, with AGN completeness around 85.42% - 88.53% and SFG completeness around 81.17% - 85.09%., Comment: 12 pages, 12 figures

In order to understand the interaction between the central black hole and the whole galaxy or their co-evolution history along with cosmic time, a complete census of active galactic nuclei (AGN) is crucial. However, AGNs are often missed in optical, UV and soft X-ray observations since they could be obscured by gas and dust. A mid-infrared (mid-IR) survey supported by multiwavelength data is one of the best ways to find obscured AGN activities because it suffers less from extinction. Previous large IR photometric surveys, e.g., $WISE$ and $Spitzer$, have gaps between the mid-IR filters. Therefore, star forming galaxy (SFG)-AGN diagnostics in the mid-IR were limited. The $AKARI$ satellite has a unique continuous 9-band filter coverage in the near to mid-IR wavelengths. In this work, we take advantage of the state-of-the-art spectral energy distribution (SED) modelling software, CIGALE, to find AGNs in mid-IR. We found 126 AGNs in the NEP-Wide field with this method. We also investigate the energy released from the AGN as a fraction of the total IR luminosity of a galaxy. We found that the AGN contribution is larger at higher redshifts for a given IR luminosity. With the upcoming deep IR surveys, e.g., $JWST$, we expect to find more AGNs with our method., 14 pages, 18 figures. Accepted for publication in MNRAS. For associated video, please see https://www.youtube.com/watch?v=B01jL0Bol9Q&feature=emb_logo

The $AKARI$ infrared (IR) space telescope conducted two surveys (Deep and Wide) in the North Ecliptic Pole (NEP) field to find more than 100,000 IR sources using its Infrared Camera (IRC). IRC's 9 filters, which cover wavebands from 2 to 24 $\mu$m continuously, make $AKARI$ unique in comparison with other IR observatories such as $Spitzer$ or $WISE$. However, studies of the $AKARI$ NEP-Wide field sources had been limited due to the lack of follow-up observations in the ultraviolet (UV) and optical. In this work, we present the Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam $u$-band source catalogue of the $AKARI$ NEP-Wide field. The observations were taken in 7 nights in 2015 and 2016, resulting in 82 observed frames covering 3.6 deg$^2$. The data reduction, image processing and source extraction were performed in a standard procedure using the \textsc{Elixir} pipeline and the \textsc{AstrOmatic} software, and eventually 351,635 sources have been extracted. The data quality is discussed in two regions (shallow and deep) separately, due to the difference in the total integration time (4,520 and 13,910 seconds). The 5$\sigma$ limiting magnitude, seeing FWHM, and the magnitude at 50 per cent completeness are 25.38 mag (25.79 mag in the deep region), 0.82 arcsec (0.94 arcsec) and 25.06 mag (25.45 mag), respectively. The u-band data provide us with critical improvements to photometric redshifts and UV estimates of the precious infrared sources from the $AKARI$ space telescope., Comment: 13 pages, 14 figures, accepted for publication in MNRAS

By utilizing large-scale graph analytic tools implemented in the modern Big Data platform, Apache Spark, we investigate the topological structure of gravitational clustering in five different universes produced by cosmological $N$-body simulations with varying parameters: (1) a WMAP 5-year compatible $\Lambda$CDM cosmology, (2) two different dark energy equation of state variants, and (3) two different cosmic matter density variants. For the Big Data calculations, we use a custom build of stand-alone Spark/Hadoop cluster at Korea Institute for Advanced Study (KIAS) and Dataproc Compute Engine in Google Cloud Platform (GCP) with the sample size ranging from 7 millions to 200 millions. We find that among the many possible graph-topological measures, three simple ones: (1) the average of number of neighbors (the so-called average vertex degree) $\alpha$, (2) closed-to-connected triple fraction (the so-called transitivity) $\tau_\Delta$, and (3) the cumulative number density $n_{s\ge5}$ of subcomponents with connected component size $s \ge 5$, can effectively discriminate among the five model universes. Since these graph-topological measures are in direct relation with the usual $n$-points correlation functions of the cosmic density field, graph-topological statistics powered by Big Data computational infrastructure opens a new, intuitive, and computationally efficient window into the dark Universe., Comment: 16 pages, 11 figures, submitted to MNRAS

We present the star formation rate (SFR) measurements based on the spectral energy distribution (SED) analysis with new sub-mm fluxes combined with archival multi-wavelength data for a sample of 52 AGN host galaxies at z $, Comment: Accepted for publication in ApJ (Feb. 9th, 2022). 23 pages, 15 figures

HectoMAP is a dense redshift survey of 95,403 galaxies based primarily on MMT spectroscopy with a median redshift $z = 0.345$. The survey covers 54.64 square degrees in a 1.5$^\circ$ wide strip across the northern sky centered at a declination of 43.25$^\circ$. We report the redshift, the spectral indicator D$_{n}$4000, and the stellar mass. The red selected survey is 81\% complete for 55,962 galaxies with $(g-r) > 1$ and $r 1$, $(r-i) > 0.5$ and $20.5 < r < 21.3$. Comparison of the survey basis SDSS photometry with the HSC-SSP photometry demonstrates that HectoMAP provides complete magnitude limited surveys based on either photometric system. We update the comparison between the HSC-SSP photometric redshifts with HectoMAP spectroscopic redshifts; the comparison demonstrates that the HSC-SSP photometric redshifts have improved between the second and third data releases. HectoMAP is a foundation for examining the quiescent galaxy population (63\% of the survey), clusters of galaxies, and the cosmic web. HectoMAP is completely covered by the HSC-SSP survey, thus enabling a variety of strong and weak lensing investigations., Accepted for publication in The Astrophysical Journal. 22 pages, 16 figures, 3 tables. The full dataset for HectoMAP will be available when the paper is published

To understand how well galaxies, gas and intracluster stars trace dark matter in and around galaxy clusters, we use the IllustrisTNG cosmological hydrodynamical simulation and compare the spatial distribution of dark matter with those of baryonic components in clusters. To quantify the global morphology of the density distribution of each component in clusters, we fit an ellipse to the density contour of each component and derive shape parameters at different radii. We find that ellipticity of dark matter is better correlated with that of galaxy mass-weighted number density, rather than with that of galaxy number density or galaxy velocity dispersion. We thus use the galaxy mass-weighted number density map as a representative of the galaxy maps. Among three different density maps from galaxies, gas, and intracluster stars, the ellipticity of dark matter is best reproduced by that of the galaxy map over the entire radii. The 'virialized' galaxy clusters show a better correlation of spatial distribution between dark matter and other components than the 'unvirialized' clusters, suggesting that it requires some time for each component to follow the spatial distribution of dark matter after merging events. Our results demonstrate that galaxies are still good tracers of dark matter distribution even in the non-linear regime corresponding to the scales in and around galaxy clusters, being consistent with the case where galaxies trace well the matter distribution in cosmologically large scales., Comment: accepted for publication in ApJ

We study the cold gas and dust properties for a sample of red star forming galaxies called "red misfits." We collect single-dish CO observations and HI observations from representative samples of low-redshift galaxies, as well as our own JCMT CO observations of red misfits. We also obtain SCUBA-2 850 um observations for a subset of these galaxies. With these data we compare the molecular gas, total cold gas, and dust properties of red misfits against those of their blue counterparts ("blue actives") taking non-detections into account using a survival analysis technique. We compare these properties at fixed position in the log SFR-log M* plane, as well as versus offset from the star-forming main sequence. Compared to blue actives, red misfits have slightly longer molecular gas depletion times, similar total gas depletion times, significantly lower molecular- and total-gas mass fractions, lower dust-to-stellar mass ratios, similar dust-to-gas ratios, and a significantly flatter slope in the $\log M_\mathrm{mol}$-$\log M_\star$ plane. Our results suggest that red misfits as a population are likely quenching due to a shortage in gas supply., Comment: 16 pages, 7 Figures, accepted to MNRAS

We investigate the variation in the mid-infrared spectral energy distributions of 373 low-redshift ($z, 19 pages, 9 figures, AJ, in press

We present the results from the analysis of galaxy rotation curves with Verlinde's emergent gravity. We use the data in the SPARC (Spitzer Photometry and Accurate Rotation Curves) database, which contains a sample of 175 nearby disk galaxies with 3.6 $\mu$m surface photometry and rotation curves. We compute the gravitational acceleration at different galactocentric radii expected from the baryon distribution of the galaxies with the emergent gravity, and compare it with the observed gravitational acceleration derived from galactic rotation curves. The predicted and observed accelerations agree well with a mean offset $\mu{\rm [log(g_{obs})-log(g_{Ver})]}=-0.060\pm0.004$ and a scatter $\sigma{\rm [log(g_{obs})-log(g_{Ver})]}=0.137\pm0.004$ by assuming a de Sitter universe. These offset and scatter become smaller when we assume a more realistic universe, quasi de Sitter universe, as $\mu=-0.027\pm0.003$ and $\sigma=0.129\pm0.003$. Our results suggest that Verlinde's emergent gravity could be a good solution to the missing mass problem without introducing dark matter., Comment: 11 pages, 2 figures. To appear in Classical and Quantum Gravity

Abdurro’uf et al., This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys., This publication uses data generated via the Zooniverse.org platform, development of which is funded by generous support, including a Global Impact Award from Google, and by a grant from the Alfred P. Sloan Foundation. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

In a galaxy cluster, the relative spatial distributions of dark matter, member galaxies, gas, and intracluster light (ICL) may connote their mutual interactions over the cluster evolution. However, it is a challenging problem to provide a quantitative measure for the shape matching between two multi-dimensional scalar distributions. We present a novel methodology, named the {\em Weighted Overlap Coefficient (WOC)}, to quantify the similarity of 2-dimensional spatial distributions. We compare the WOC with a standard method known as the Modified Hausdorff Distance (MHD). We find that our method is robust, and performs well even with the existence of multiple sub-structures. We apply our methodology to search for a visible component whose spatial distribution resembled with that of dark matter. If such a component could be found to trace the dark matter distribution with high fidelity for more relaxed galaxy clusters, then the similarity of the distributions could also be used as a dynamical stage estimator of the cluster. We apply the method to six galaxy clusters at different dynamical stages simulated within the GRT simulation, which is an N-body simulation using the galaxy replacement technique. Among the various components (stellar particles, galaxies, ICL), the ICL+ brightest cluster galaxy (BCG) component most faithfully trace the dark matter distribution. Among the sample galaxy clusters, the relaxed clusters show stronger similarity in the spatial distribution of the dark matter and ICL+BCG than the dynamically young clusters. While the MHD results show weaker trend with the dynamical stages., 17 pages, 8 figures, accepted in ApJS

We examine the robustness of the color-color selection of quiescent galaxies (QGs) against contamination of dusty star-forming galaxies using the latest submillimeter data. We selected 18,304 QG candidates out to $z\sim$ 3 using the commonly adopted $NUV-r-J$ selection based on the high-quality multi-wavelength COSMOS2015 catalog. Using extremely deep 450 and 850 $\mu$m catalogs from the latest JCMT SCUBA-2 Large Programs, S2COSMOS, and STUDIES, as well as ALMA submillimeter, VLA 3 GHz, and $Spitzer$ MIPS 24 $\mu$m catalogs, we identified luminous dusty star-forming galaxies among the QG candidates. We also conducted stacking analyses in the SCUBA-2 450 and 850 $\mu$m images to look for less-luminous dusty galaxies among the QG candidates. By cross-matching to the 24 $\mu$m and 3 GHz data, we were able to identify a sub-group of "IR-radio-bright" QGs who possess a strong 450 and 850 $\mu$m stacking signal. The potential contamination of these luminous and less-luminous dusty galaxies accounts for approximately 10% of the color-selected QG candidates. In addition, there exists a spatial correlation between the luminous star-forming galaxies and the QGs at a $\lesssim60$ kpc scale. Finally, we found a high QG fraction among radio AGNs at $z, Comment: This paper is accepted for publication on ApJ

The $AKARI$ space infrared telescope has performed near- to mid-infrared (MIR) observations on the North Ecliptic Pole Wide (NEPW) field (5.4 deg$^2$) for about one year. $AKARI$ took advantage of its continuous nine photometric bands, compared with NASA's $Spitzer$ and WISE space telescopes, which had only four filters with a wide gap in the MIR. The $AKARI$ NEPW field lacked deep and homogeneous optical data, limiting the use of nearly half of the IR sources for extra-galactic studies owing to the absence of photometric redshifts (photo-zs). To remedy this, we have recently obtained deep optical imaging over the NEPW field with 5 bands ($g$, $r$, $i$, $z$, and $Y$) of the Hyper Suprime-Camera (HSC) on the Subaru 8m telescope. We optically identify AKARI-IR sources along with supplementary $Spitzer$ and WISE data as well as pre-existing optical data. In this work, we derive new photo-zs using a $\chi^2$ template-fitting method code ($Le$ $Phare$) and reliable photometry from 26 selected filters including HSC, $AKARI$, CFHT, Maidanak, KPNO, $Spitzer$ and WISE data. We take 2026 spectroscopic redshifts (spec-z) from all available spectroscopic surveys over the NEPW to calibrate and assess the accuracy of the photo-zs. At z < 1.5, we achieve a weighted photo-z dispersion of $\sigma_{\Delta{z/(1+z)}}$ = 0.053 with $\eta$ = 11.3% catastrophic errors., Comment: 20 pages, 13 figures, accepted for publication in MNRAS. For summary video, please see http://youtu.be/hjNJRCoBIgg

We measure the genus of the galaxy distribution in two-dimensional slices of the SDSS-III BOSS catalog to constrain the cosmological parameters governing the expansion history of the Universe. The BOSS catalogs are divided into twelve concentric shells over the redshift range $0.25 < z < 0.6$ and we repeatedly measure the genus from the two-dimensional galaxy density fields, each time varying the cosmological parameters used to infer the distance-redshift relation to the shells. We also indirectly reconstruct the two-dimensional genus amplitude using the three-dimensional genus measured from SDSS Main Galaxy Sample with galaxies at low redshift $z < 0.12$. We combine the low- and high-redshift measurements, finding the cosmological model which minimizes the redshift evolution of the genus amplitude, using the fact that this quantity should be conserved. Being a distance measure, the test is sensitive to the matter density parameter ($��_{\rm m}$) and equation of state of dark energy ($w_{\rm de}$). We find a constraint of $w_{\rm de} = -1.05^{+0.13}_{-0.12}$, $��_{\rm m} = 0.303 \pm 0.036$ after combining the high- and low-redshift measurements and combining with Planck CMB data. Higher redshift data and combining data sets at low redshift will allow for stronger constraints., Accepted for publication in the Astrophysical Journal. 19 pages, 13 figures

Context. The North Ecliptic Pole (NEP) field provides a unique set of panchromatic data, well suited for active galactic nuclei (AGN) studies. Selection of AGN candidates is often based on mid-infrared (MIR) measurements. Such method, despite its effectiveness, strongly reduces a catalog volume due to the MIR detection condition. Modern machine learning techniques can solve this problem by finding similar selection criteria using only optical and near-infrared (NIR) data. Aims. Aims of this work were to create a reliable AGN candidates catalog from the NEP field using a combination of optical SUBARU/HSC and NIR AKARI/IRC data and, consequently, to develop an efficient alternative for the MIR-based AKARI/IRC selection technique. Methods. A set of supervised machine learning algorithms was tested in order to perform an efficient AGN selection. Best of the models were formed into a majority voting scheme, which used the most popular classification result to produce the final AGN catalog. Additional analysis of catalog properties was performed in form of the spectral energy distribution (SED) fitting via the CIGALE software. Results. The obtained catalog of 465 AGN candidates (out of 33 119 objects) is characterized by 73% purity and 64% completeness. This new classification shows consistency with the MIR-based selection. Moreover, 76% of the obtained catalog can be found only with the new method due to the lack of MIR detection for most of the new AGN candidates. Training data, codes and final catalog are available via the github repository. Final AGN candidates catalog will be also available via the CDS service after publication., Comment: Accepted for publication in Astronomy and Astrophysics

To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars and cluster galaxies from the SDSS. With ~82 000 quasar spectra, we detect 197 MgII absorbers in and around the clusters. The detection rate per quasar is 2.7$\pm$0.7 times higher inside the clusters than outside the clusters, indicating that MgII absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that MgII absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30$\pm$10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster., Comment: 11 pages, 12 figures. To appear in MNRAS

We study the stellar and gas kinematics of the brightest group galaxies (BGGs) in dynamically relaxed and unrelaxed galaxy groups for a sample of 154 galaxies in the SAMI galaxy survey. We characterize the dynamical state of the groups using the luminosity gap between the two most luminous galaxies and the BGG offset from the luminosity centroid of the group. We find that the misalignment between the rotation axis of gas and stellar components is more frequent in the BGGs in unrelaxed groups, although with quite low statistical significance. Meanwhile galaxies whose stellar dynamics would be classified as `regular rotators' based on their kinemetry are more common in relaxed groups. We confirm that this dependency on group dynamical state remains valid at fixed stellar mass and Sersic index. The observed trend could potentially originate from a differing BGG accretion history in virialised and evolving groups. Amongst the halo relaxation probes, the group BGG offset appears to play a stronger role than the luminosity gap on the stellar kinematic differences of the BGGs. However, both the group BGG offset and luminosity gap appear to roughly equally drive the misalignment between the gas and stellar component of the BGGs in one direction. This study offers the first evidence that the dynamical state of galaxy groups may influence the BGG's stellar and gas kinematics and calls for further studies using a larger sample with higher signal-to-noise., 16 pages, 12 figures. Accepted for publication in ApJ

We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The HORIZON-AGN simulation is analysed at z~2 using the DISPERSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts., 22 pages, 18 figures, accepted to MNRAS, comments are welcome

We measure the central stellar velocity dispersion function for quiescent galaxies in a set of nine northern clusters in the redshift range $0.18 < z < 0.29$ and with strong lensing arcs in Hubble Space Telescope images. The velocity dispersion function links galaxies directly to their dark matter halos. From dense SDSS and MMT/Hectospec spectroscopy we identify $231 - 479$ spectroscopic members in each cluster. We derive physical properties of cluster members including redshift, $D_{n}4000$, and central stellar velocity dispersion and we include a table of these measurements for 3419 cluster members. We construct the velocity dispersion functions for quiescent galaxies with $D_{n}4000 > 1.5$ and within $R_{200}$. The cluster velocity dispersion functions all show excesses at $��\gtrsim 250 km s^{-1}$ compared to the field velocity dispersion function. The velocity dispersion function slope at large velocity dispersion ($��> 160 km s^{-1}$) is steeper for more massive clusters, consistent with the trend observed for cluster luminosity functions. The spatial distribution of galaxies with large velocity dispersion at radii larger than $R_{200}$ further underscores the probable major role of dry mergers in the growth of massive cluster galaxies during cluster assembly., 16 pages, 12 figures, Accepted for publication in the ApJ

Scaling laws of dust, HI gas and metal mass with stellar mass, specific star formation rate and metallicity are crucial to our understanding of the buildup of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass ($M_{\text{HI}}$/$M_{\star}$) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - incluidng stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multi-dimensional parameter space. We find that these scaling laws for galaxies with $-1.0\lesssim \log M_{\text{HI}}$/$M_{\star}\lesssim0$ can be reproduced using closed-box models with high fractions (37-89$\%$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies ($\epsilon$=30-40), and long dus lifetimes (1-2\,Gyr). The models have present-day dust masses with similar contributions from stellar sources (50-80\,$\%$) and grain growth (20-50\,$\%$). Over the entire lifetime of these galaxies, the contribution from stardust ($>$90\,$\%$) outweighs the fraction of dust grown in the interstellar medium ($, Comment: 56 pages, 30 figures, accepted for publication in MNRAS

We investigate the impact of the number of filaments connected to the nodes of the cosmic web on the physical properties of their galaxies using the Sloan Digital Sky Survey. We compare these measurements to the cosmological hydrodynamical simulations Horizon-(no)AGN and Simba. We find that more massive galaxies are more connected, in qualitative agreement with theoretical predictions and measurements in dark matter only simulation. The star formation activity and morphology of observed galaxies both display some dependence on the connectivity of the cosmic web at fixed stellar mass: less star forming and less rotation supported galaxies also tend to have higher connectivity. These results qualitatively hold both for observed and virtual galaxies, and can be understood given that the cosmic web is the main source of fuel for galaxy growth. The simulations show the same trends at fixed halo mass, suggesting that the geometry of filamentary infall impacts galaxy properties beyond the depth of the local potential well. Based on simulations, it is also found that AGN feedback is key in reversing the relationship between stellar mass and connectivity at fixed halo mass. Technically, connectivity is a practical observational proxy for past and present accretion (minor mergers or diffuse infall)., Comment: 16 pages, 15 figures, submitted to MNRAS

We present measurements of the two-dimensional genus of the SDSS-III BOSS catalogs to constrain cosmological parameters governing the shape of the matter power spectrum. The BOSS data are divided into twelve concentric shells over the redshift range $0.2 < z < 0.6$, and we extract the genus from the projected two-dimensional galaxy density fields. We compare the genus amplitudes to their Gaussian expectation values, exploiting the fact that this quantity is relatively insensitive to non-linear gravitational collapse. The genus amplitude provides a measure of the shape of the linear matter power spectrum, and is principally sensitive to $\Omega_{\rm c}h^{2}$ and scalar spectral index $n_{\rm s}$. A strong negative degeneracy between $\Omega_{\rm c}h^{2}$ and $n_{\rm s}$ is observed, as both can increase small scale power by shifting the peak and tilting the power spectrum respectively. We place a constraint on the particular combination $n_{\rm s}^{3/2} \Omega_{\rm c}h^{2}$ -- we find $n_{\rm s}^{3/2} \Omega_{\rm c}h^{2} = 0.1121 \pm 0.0043$ after combining the LOWZ and CMASS data sets, assuming a flat $\Lambda$CDM cosmology. This result is practically insensitive to reasonable variations of the power spectrum amplitude and linear galaxy bias. Our results are consistent with the Planck best fit $n_{\rm s}^{3/2}\Omega_{\rm c}h^{2} = 0.1139 \pm 0.0009$., Comment: ApJ submitted, comments welcome

We analyse the physical properties of 121 SNR $\geq$ 5 sub-millimetre galaxies (SMGs) from the STUDIES 450-$\mu$m survey. We model their UV-to-radio spectral energy distributions using MAGPHYS+photo-$z$ and compare the results to similar modelling of 850-$\mu$m-selected SMG sample from AS2UDS, to understand the fundamental physical differences between the two populations at the observed depths. The redshift distribution of the 450-$\mu$m sample has a median of $z$ = 1.85 $\pm$ 0.12 and can be described by strong evolution of the far-infrared luminosity function. The fainter 450-$\mu$m sample has $\sim$14 times higher space density than the brighter 850-$\mu$m sample at $z$ $\lesssim$2, and a comparable space density at $z$ = 2-3, before rapidly declining, suggesting LIRGs are the main obscured population at $z$ $\sim$ 1-2, while ULIRGs dominate at higher redshifts. We construct rest-frame $\sim$ 180-$\mu$m-selected and dust-mass-matched samples at $z$ = 1-2 and $z$ = 3-4 from the 450-$\mu$m and 850-$\mu$m samples, respectively, to probe the evolution of a uniform sample of galaxies spanning the cosmic noon era. Using far-infrared luminosity, dust masses and an optically-thick dust model, we suggest that higher-redshift sources have higher dust densities due to inferred dust continuum sizes which are roughly half of those for the lower-redshift population at a given dust mass, leading to higher dust attenuation. We track the evolution in the cosmic dust mass density and suggest that the dust content of galaxies is governed by a combination of both the variation of gas content and dust destruction timescale., Comment: 20 pages, 7 figures, MNRAS accepted

The 80% of the matter in the Universe is in the form of dark matter that comprises the skeleton of the large-scale structure called the Cosmic Web. As the Cosmic Web dictates the motion of all matter in galaxies and inter-galactic media through gravity, knowing the distribution of dark matter is essential for studying the large-scale structure. However, the Cosmic Web's detailed structure is unknown because it is dominated by dark matter and warm-hot inter-galactic media, both of which are hard to trace. Here we show that we can reconstruct the Cosmic Web from the galaxy distribution using the convolutional-neural-network-based deep-learning algorithm. We find the mapping between the position and velocity of galaxies and the Cosmic Web using the results of the state-of-the-art cosmological galaxy simulations, Illustris-TNG. We confirm the mapping by applying it to the EAGLE simulation. Finally, using the local galaxy sample from Cosmicflows-3, we find the dark-matter map in the local Universe. We anticipate that the local dark-matter map will illuminate the studies of the nature of dark matter and the formation and evolution of the Local Group. High-resolution simulations and precise distance measurements to local galaxies will improve the accuracy of the dark-matter map., Comment: 18 pages, 9 figures, ApJ accepted, added more data analyses

We develop a method to identify cosmic voids from the matter density field by adopting a physically-motivated concept that voids are the counterpart of massive clusters. To prove the concept we use a pair of $\Lambda$CDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. Galaxy cluster-scale dark matter halos are identified in the Mirror simulation at $z=0$ by linking dark matter particles. The void corresponding to each cluster is defined in the Reference simulation as the region occupied by the member particles of the cluster. We study the voids corresponding to the halos more massive than $10^{13}h^{-1}M_{\odot}$. We find a power-law scaling relation between the void size and the corresponding cluster mass. Voids with corresponding cluster mass above $10^{15}h^{-1}M_{\odot}$ occupy $\sim1\%$ of the total simulated volume, whereas this fraction increases to $\sim54\%$ for voids with corresponding cluster mass above $10^{13}h^{-1}M_{\odot}$. It is also found that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter density field without their mirror information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We recover voids corresponding to clusters more massive than $3\times10^{14}h^{-1}M_{\odot}$ at 70--74 \% level of completeness and reliability. Our results suggest that we are able to identify voids in a way to associate them with clusters of a particular mass-scale., Comment: Published in ApJ

We apply a friends-of-friends (FoF) algorithm to identify galaxy clusters and we use the catalog to explore the evolutionary synergy between BCGs and their host clusters. We base the cluster catalog on the dense HectoMAP redshift survey (2000 redshifts deg$^{-2}$). The HectoMAP FoF catalog includes 346 clusters with 10 or more spectroscopic members. We list these clusters and their members (5992 galaxies with a spectroscopic redshift). We also include central velocity dispersions ($\sigma_{*, BCG}$) for all of the FoF cluster BCGs, a distinctive feature of the HectoMAP FoF catalog. HectoMAP clusters with higher galaxy number density (80 systems) are all genuine clusters with a strong concentration and a prominent BCG in Subaru/Hyper Suprime-Cam images. The phase-space diagrams show the expected elongation along the line-of-sight. Lower-density systems include some false positives. We establish a connection between BCGs and their host clusters by demonstrating that $\sigma_{*,BCG}/\sigma_{cl}$ decreases as a function of cluster velocity dispersion ($\sigma_{cl}$), in contrast, numerical simulations predict a constant $\sigma_{*, BCG}/\sigma_{cl}$. Sets of clusters at two different redshifts show that BCG evolution in massive systems is slow over the redshift range $z < 0.4$. The data strongly suggest that minor mergers may play an important role in BCG evolution in these clusters ($\sigma_{cl} \gtrsim 300$ km s$^{-1}$). For systems of lower mass ($\sigma_{cl} < 300$ km s$^{-1}$), the data indicate that major mergers may play a significant role. The coordinated evolution of BCGs and their host clusters provides an interesting test of simulations in high density regions of the universe., Comment: 20 pages, 16 figures, 3 tables. Submitted to the ApJ

We study the stellar populations of the brightest group galaxies (BGGs) in groups with different dynamical states, using GAMA survey data. We use two independent, luminosity dependent indicators to probe the relaxedness of their groups; the magnitude gap between the two most luminous galaxies ($\Delta M_{12}$), and offset between BGG and the luminosity center ($D_{offset}$) of the group. Combined, these two indicators were previously found useful for identifying relaxed and unrelaxed groups. We find that the BGGs of unrelaxed groups have significantly bluer NUV-r colours than in relaxed groups. This is also true at the fixed sersic index. We find the bluer colours cannot be explained away by differing dust fraction, suggesting there are real differences in their stellar populations. SFRs derived from SED-fitting tend to be higher in unrelaxed systems. This is in part because of a greater fraction of BGGs with non-elliptical morphology, but also because unrelaxed systems have larger numbers of mergers, some of which may bring fuel for star formation. The SED-fitted stellar metallicities of BGGs in unrelaxed systems also tend to be higher by around 0.05 dex, perhaps because their building blocks were more massive. We find that the $\Delta M_{12}$ parameter is the most important parameter behind the observed differences in the relaxed/unrelaxed groups, in contrast with the previous study of Trevisan et al. (2017). We also find that groups selected to be unrelaxed using our criteria tend to have higher velocity offsets between the BGG and their group., Comment: 12 pages, 11 figures, Accepted for publication in ApJ

We present CO(J=1-0) and/or CO(J=2-1) spectroscopy for 31 galaxies selected from the ongoing MaNGA survey, obtained with multiple telescopes. This sample is combined with CO observations from the literature to study the correlation of the CO luminosities ($L_{\rm CO(1-0)}$) with the mid-infrared luminosities at 12 ($L_{12 \mu m}$) and 22 $\mu$m ($L_{\rm 22 \mu m}$), as well as the dependence of the residuals on a variety of galaxy properties. The correlation with $L_{\rm 12 \mu m}$ is tighter and more linear, but galaxies with relatively low stellar masses and blue colors fall significantly below the mean $L_{\rm CO(1-0)}-L_{\rm 12\mu m}$ relation. We propose a new estimator of the CO(1-0) luminosity (and thus the total molecular gas mass) that is a linear combination of three parameters: $L_{\rm 12 \mu m}$, $M_\ast$ and $g-r$. We show that, with a scatter of only 0.18 dex in log $(L_{\rm CO(1-0)})$, this estimator provides unbiased estimates for galaxies of different properties and types. An immediate application of this estimator to a compiled sample of galaxies with only CO(J=2-1) observations yields a distribution of the CO(J=2-1) to CO(J=1-0) luminosity ratios ($R21$) that agrees well with the distribution of real observations, in terms of both the median and the shape. Application of our estimator to the current MaNGA sample reveals a gas-poor population of galaxies that are predominantly early-type and show no correlation between molecular gas-to-stellar mass ratio and star formation rate, in contrast to gas-rich galaxies. We also provide alternative estimators with similar scatters, based on $r$ and/or $z$ band luminosities instead of $M_\ast$. These estimators serve as cheap and convenient $M_{\rm mol}$ proxies to be potentially applied to large samples of galaxies, thus allowing statistical studies of gas-related processes of galaxies., Comment: 24 pages, 12 figures, accepted for publication in ApJ

We study the dust properties of 192 nearby galaxies from the JINGLE survey using photometric data in the 22-850micron range. We derive the total dust mass, temperature T and emissivity index beta of the galaxies through the fitting of their spectral energy distribution (SED) using a single modified black-body model (SMBB). We apply a hierarchical Bayesian approach that reduces the known degeneracy between T and beta. Applying the hierarchical approach, the strength of the T-beta anti-correlation is reduced from a Pearson correlation coefficient R=-0.79 to R=-0.52. For the JINGLE galaxies we measure dust temperatures in the range 17-30 K and dust emissivity indices beta in the range 0.6-2.2. We compare the SMBB model with the broken emissivity modified black-body (BMBB) and the two modified black-bodies (TMBB) models. The results derived with the SMBB and TMBB are in good agreement, thus applying the SMBB, which comes with fewer free parameters, does not penalize the measurement of the cold dust properties in the JINGLE sample. We investigate the relation between T and beta and other global galaxy properties in the JINGLE and Herschel Reference Survey (HRS) sample. We find that beta correlates with the stellar mass surface density (R=0.62) and anti-correlates with the HI mass fraction (M(HI)/M*, R=-0.65), whereas the dust temperature correlates strongly with the SFR normalized by the dust mass (R=0.73). These relations can be used to estimate T and beta in galaxies with insufficient photometric data available to measure them directly through SED fitting., MNRAS in press, 31 pages

We present Atacama Large Millimetre Array and Atacama Compact Array observations of the Sunyaev-Zel'dovich effect in the z = 2 galaxy cluster Cl J1449+0856, an X-ray-detected progenitor of typical massive clusters in the present day Universe. While in a cleaned but otherwise untouched 92 GHz map of this cluster, little to no negative signal is visible, careful subtraction of known sub-millimetre emitters in the uv plane reveals a decrement at 5$\sigma$ significance. The total signal is -190$\pm$36 $\mu$Jy, with a peak offset by 5"-9" ($\sim$50 kpc) from both the X-ray centroid and the still-forming brightest cluster galaxy. A comparison of the recovered uv-amplitude profile of the decrement with different pressure models allows us to derive total mass constraints consistent with the $\sim$6$\times$10$^{13}$ M$_{\odot}$ estimated from X-ray data. Moreover, we find no strong evidence for a deviation of the pressure profile with respect to local galaxy clusters, although a slight tension at small-to-intermediate spatial scales suggests a flattened central profile, opposite to what seen in a cool core and possibly an AGN-related effect. This analysis of the lowest mass single SZ detection so far illustrates the importance of interferometers when observing the SZ effect in high-redshift clusters, the cores of which cannot be considered quiescent, such that careful subtraction of galaxy emission is necessary., Comment: 11 pages, 6 figures (+appendices); accepted for publication in Astronomy & Astrophysics

We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)-density relation over cosmic time. We construct several samples of galaxies at different redshifts from $z=2.0$ to $z=0.0$, which have the same comoving number density. The SFR of galaxies decreases with local density at $z=0.0$, but its dependence on local density becomes weaker with redshift. At $z\gtrsim1.0$, the SFR of galaxies increases with local density (reversal of the SFR-density relation), and its dependence becomes stronger with redshift. This change of SFR-density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, $z\sim1.5$, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at $z=0.0-2.0$ even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR-density relation at $z\gtrsim1.0$ can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe., 10 pages, 8 figures. To appear in MNRAS. Paper with high resolution figures is available at https://astro.kias.re.kr/~hshwang/Hwang_etal2019_TNG_Reversal_HR.pdf

We identify multi-wavelength counterparts to 1,147 submillimeter sources from the S2COSMOS SCUBA-2 survey of the COSMOS field by employing a recently developed radio$+$machine-learning method trained on a large sample of ALMA-identified submillimeter galaxies (SMGs), including 260 SMGs identified in the AS2COSMOS pilot survey. In total, we identify 1,222 optical/near-infrared(NIR)/radio counterparts to the 897 S2COSMOS submillimeter sources with S$_{850}$>1.6mJy, yielding an overall identification rate of ($78\pm9$)%. We find that ($22\pm5$)% of S2COSMOS sources have multiple identified counterparts. We estimate that roughly 27% of these multiple counterparts within the same SCUBA-2 error circles very likely arise from physically associated galaxies rather than line-of-sight projections by chance. The photometric redshift of our radio$+$machine-learning identified SMGs ranges from z=0.2 to 5.7 and peaks at $z=2.3\pm0.1$. The AGN fraction of our sample is ($19\pm4$)%, which is consistent with that of ALMA SMGs in the literature. Comparing with radio/NIR-detected field galaxy population in the COSMOS field, our radio+machine-learning identified counterparts of SMGs have the highest star-formation rates and stellar masses. These characteristics suggest that our identified counterparts of S2COSMOS sources are a representative sample of SMGs at z, 24 pages, 14 figures, 3 tables, resubmitted to ApJ

The strikingly anisotropic large-scale distribution of matter made of an extended network of voids delimited by sheets, themselves segmented by filaments, within which matter flows towards compact nodes where they intersect, imprints its geometry on the dynamics of cosmic flows, ultimately shaping the distribution of galaxies and the redshift evolution of their properties. The (filament-type) saddle points of this cosmic web provide a local frame in which to quantify the induced physical and morphological evolution of galaxies on large scales. The properties of virtual galaxies within the Horizon-AGN simulation are stacked in such a frame. The iso-contours of the galactic number density, mass, specific star formation rate (sSFR), kinematics and age are clearly aligned with the filament axis with steep gradients perpendicular to the filaments. A comparison to a simulation without feedback from active galactic nuclei (AGN) illustrates its impact on quenching star formation of centrals away from the saddles. The redshift evolution of the properties of galaxies and their age distribution are consistent with the geometry of the bulk flow within that frame. They compare well with expectations from constrained Gaussian random fields and the scaling with the mass of non-linearity, modulo the redshift dependent impact of feedback processes. Physical properties such as sSFR and kinematics seem not to depend only on mean halo mass and density: the residuals trace the geometry of the saddle, which could point to other environment-sensitive physical processes, such as spin advection, and AGN feedback at high mass., Comment: 28 pages, 27 figures, submitted to MNRAS

HectoMAP is a dense, red-selected redshift survey to a limiting $r = 21.3$ covering 55 square degrees in a contiguous 1.5$^\circ$ strip across the northern sky. This region is also covered by the Subaru/Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) photometric survey enabling a range of applications that combine a dense foreground redshift survey with both strong and weak lensing maps. The median redshift of HectoMAP exceeds 0.3 throughout the survey region and the mean density of the redshift survey is $\sim 2000$ galaxies deg$^{-2}$. Here we report a total of 17,313 redshifts in a first data release covering 8.7 square degrees. We include the derived quantities D$_{n}4000$ and stellar mass for nearly all of the objects. Among these galaxies, 8117 constitute a 79\% complete red-selected subsample with $r \leq 20.5$ and an additional 4318 constitute a 68\% complete red-selected subsample with $20.5 < r < 21.3$. As examples of the strengths of HectoMAP data we discuss two applications: refined membership of redMaPPer photometrically selected clusters and a test of HSC photometric redshifts. We highlight a remarkable redMaPPer strong lensing system. The comparison of photometric redshifts with spectroscopic redshifts in a dense survey uncovers subtle systematic issues in the photometric redshifts., 21 pages, 16 figures, ApJ submitted

We present the physical properties of AKARI sources without optical counterparts in optical images from the Hyper Suprime-Cam (HSC) on the Subaru telescope. Using the AKARI infrared (IR) source catalog and HSC optical catalog, we select 583 objects that do not have HSC counterparts in the AKARI North Ecliptic Pole (NEP) wide survey field ($\sim 5$ deg$^{2}$). Because the HSC limiting magnitude is deep ($g_{\rm AB}$ $\sim 28.6$), these are good candidates for extremely red star-forming galaxies (SFGs) and/or active galactic nuclei (AGNs), possibly at high redshifts. We compile multi-wavelength data out to 500 $\mu$m and use it for Spectral Energy Distribution (SED) fitting with CIGALE to investigate the physical properties of AKARI galaxies without optical counterparts. We also compare their physical quantities with AKARI mid-IR selected galaxies with HSC counterparts. The estimated redshifts of AKARI objects without HSC counterparts range up to $z\sim 4$, significantly higher than that of AKARI objects with HSC counterparts. We find that: (i) 3.6 $-$ 4.5 $\mu$m color, (ii) AGN luminosity, (iii) stellar mass, (iv) star formation rate, and (v) $V$-band dust attenuation in the interstellar medium of AKARI objects without HSC counterparts are systematically larger than those of AKARI objects with counterparts. These results suggest that our sample includes luminous, heavily dust-obscured SFGs/AGNs at $z\sim 1-4$ that are missed by previous optical surveys, providing very interesting targets for the coming James Webb Space Telescope era., Comment: 17 pages, 13 figures, and 2 tables, accepted for publication in ApJ

The redshift-space distortion (RSD) in the observed distribution of galaxies is known as a powerful probe of cosmology. Observations of large-scale RSD have given tight constraints on the linear growth rate of the large-scale structures in the universe. On the other hand, the small-scale RSD, caused by galaxy random motions inside clusters, has not been much used in cosmology, but also has cosmological information because universes with different cosmological parameters have different halo mass functions and virialized velocities. We focus on the projected correlation function $w(r_p)$ and the multipole moments $\xi_l$ on small scales ($1.4$ to $30\ h^{-1}\rm{Mpc}$). Using simulated galaxy samples generated from a physically motivated most bound particle (MBP)-galaxy correspondence scheme in the Multiverse Simulation, we examine the dependence of the small-scale RSD on the cosmological matter density parameter $\Omega_m$, the satellite velocity bias with respect to MBPs, $b_v^s$, and the merger-time-scale parameter $\alpha$. We find that $\alpha=1.5$ gives an excellent fit to the $w(r_p)$ and $\xi_l$ measured from the SDSS-KIAS value added galaxy catalog. We also define the ``strength'' of Fingers-of-God as the ratio of the parallel and perpendicular size of the contour in the two-point correlation function set by a specific threshold value and show that the strength parameter helps constraining $(\Omega_m, b_v^s, \alpha)$ by breaking the degeneracy among them. The resulting parameter values from all measurements are $(\Omega_m,b_v^s)=(0.272\pm0.013,0.982\pm0.040)$, indicating a slight reduction of satellite galaxy velocity relative to the MBP. However, considering that the average MBP speed inside haloes is $0.94$ times the dark matter velocity dispersion, the main drivers behind the galaxy velocity bias are gravitational interactions, rather than baryonic effects., Comment: 18 pages, 12 figures, accepted for publication in ApJ

We qualitatively assess and map the relative contribution of pre-processing and cluster related processes to the build-up of A963, a massive cluster at z=0.2 showing an unusually high fraction of star forming galaxies in its interior. We use Voronoi binning of positions of cluster members on the plane of the sky in order to map the 2D variations of galaxy properties in the centre and infall region of A963. We map four galaxy parameters (fraction of star forming galaxies, specific star formation rate, HI deficiency and age of the stellar population) based on full SED fitting, 21cm imaging and optical spectroscopy. We find an extended region dominated by passive galaxies along a north-south axis crossing the cluster centre, possibly associated with known filaments of the large-scale structure. There are signs that the passive galaxies in this region were quenched long before their arrival in the vicinity of the cluster. Contrary to that, to the east and west of the cluster centre lie regions of recent accretion dominated by gas rich, actively star forming galaxies not associated with any substructure or filament. The few passive galaxies in this region appear to be recently quenched, and some gas rich galaxies show signs of ongoing ram-pressure stripping. We report the first tentative observations at 21cm of ongoing ram-pressure stripping at z=0.2, as well as observed inflow of low-entropy gas into the cluster along filaments of the large-scale structure. The observed galaxy content of A963 is a result of strongly anisotropic accretion of galaxies with different properties. Gas rich, star forming galaxies are being accreted from the east and west of the cluster and these galaxies are being quenched at r, Comment: A&A accepted. 14 pages, 15 figures

JINGLE is a new JCMT legacy survey designed to systematically study the cold interstellar medium of galaxies in the local Universe. As part of the survey we perform 850um continuum measurements with SCUBA-2 for a representative sample of 193 Herschel-selected galaxies with M*>10^9Msun, as well as integrated CO(2-1) line fluxes with RxA3m for a subset of 90 of these galaxies. The sample is selected from fields covered by the Herschel-ATLAS survey that are also targeted by the MaNGA optical integral-field spectroscopic survey. The new JCMT observations combined with the multi-wavelength ancillary data will allow for the robust characterization of the properties of dust in the nearby Universe, and the benchmarking of scaling relations between dust, gas, and global galaxy properties. In this paper we give an overview of the survey objectives and details about the sample selection and JCMT observations, present a consistent 30 band UV-to-FIR photometric catalog with derived properties, and introduce the JINGLE Main Data Release (MDR). Science highlights include the non-linearity of the relation between 850um luminosity and CO line luminosity, and the serendipitous discovery of candidate z>6 galaxies., MNRAS in press, 25 pages

Galaxy interactions are often accompanied by an enhanced star formation rate (SFR). Since molecular gas is essential for star formation, it is vital to establish whether, and by how much, galaxy interactions affect the molecular gas properties. We investigate the effect of interactions on global molecular gas properties by studying a sample of 58 galaxies in pairs and 154 control galaxies. Molecular gas properties are determined from observations with the JCMT, PMO, CSO telescopes, and supplemented with data from the xCOLD GASS and JINGLE surveys at $^{12}$CO(1-0) and $^{12}$CO(2-1). The SFR, gas mass ($M_\mathrm{H_{2}}$), and gas fraction ($f_{gas}$) are all enhanced in galaxies in pairs by $\sim$ 2.5 times compared to the controls matched in redshift, mass, and effective radius, while the enhancement of star formation efficiency (SFE $\equiv$ SFR/$M_{H_{2}}$) is less than a factor of 2. We also find that the enhancements in SFR, $M_{H_{2}}$ and $f_{gas}$ increase with decreasing pair separation and are larger in systems with smaller stellar mass ratio. Conversely, the SFE is only enhanced in close pairs (separation $, Comment: 26 pages, 11 figures, accepted for publication in ApJ

We study the effects of bulge elongation on the star formation activity in the centers of spiral galaxies using the data from the Sloan Digital Sky Survey Data Release 7. We construct a volume-limited sample of face-on spiral galaxies with $M_r < -$19.5 mag at 0.02 $\leq z, Comment: 9 pages, 7 figures, accepted for publication in MNRAS

We investigate environmental effects on galaxy spin using the recent public data of MaNGA integral field spectroscopic survey containing ~2800 galaxies. We measure the spin parameter of 1830 galaxies through the analysis of two-dimensional stellar kinematic maps within the effective radii, and obtain their large- (background mass density from 20 nearby galaxies) and small-scale (distance to and morphology of the nearest neighbour galaxy) environmental parameters for 1529 and 1767 galaxies, respectively. We first examine the mass dependence of galaxy spin, and find that the spin parameter of early-type galaxies decreases with stellar mass at log (M$_*/$M$_{\odot}$) $\gtrsim$ 10, consistent with the results from previous studies. We then divide the galaxies into three subsamples using their stellar masses to minimize the mass effects on galaxy spin. The spin parameters of galaxies in each subsample do not change with background mass density, but do change with distance to and morphology of the nearest neighbour. In particular, the spin parameter of late-type galaxies decreases as early-type neighbours approach within the virial radius. These results suggest that the large-scale environments hardly affect the galaxy spin, but the small-scale environments such as hydrodynamic galaxy-galaxy interactions can play a substantial role in determining galaxy spin., 12 pages, 11 figures, Accepted for publication in MNRAS

The role of the cosmic web in shaping galaxy properties is investigated in the GAMA spectroscopic survey in the redshift range $0.03 \leq z \leq 0.25$. The stellar mass, $u - r$ dust corrected colour and specific star formation rate (sSFR) of galaxies are analysed as a function of their distances to the 3D cosmic web features, such as nodes, filaments and walls, as reconstructed by DisPerSE. Significant mass and type/colour gradients are found for the whole population, with more massive and/or passive galaxies being located closer to the filament and wall than their less massive and/or star-forming counterparts. Mass segregation persists among the star-forming population alone. The red fraction of galaxies increases when closing in on nodes, and on filaments regardless of the distance to nodes. Similarly, the star-forming population reddens (or lowers its sSFR) at fixed mass when closing in on filament, implying that some quenching takes place. Comparable trends are also found in the state-of-the-art hydrodynamical simulation Horizon-AGN. These results suggest that on top of stellar mass and large-scale density, the traceless component of the tides from the anisotropic large-scale environment also shapes galactic properties. An extension of excursion theory accounting for filamentary tides provides a qualitative explanation in terms of anisotropic assembly bias: at a given mass, the accretion rate varies with the orientation and distance to filaments. It also explains the absence of type/colour gradients in the data on smaller, non-linear scales., 26 pages, 18 figures, 7 tables, accepted for publication in MNRAS

To investigate the dynamics of the galaxy cluster A2142, we compile an extended catalog of 2239 spectroscopic redshifts of sources, including 237 newly measured redshifts, within 30 arcmin from the cluster center. With the σ-plateau algorithm from the caustic method, we identify 868 members and a number of substructures in the galaxy distribution both in the outskirts, out to ∼3.5 Mpc from the cluster center, and in the central region. In the outskirts, one substructure overlaps a falling clump of gas previously identified in the X-ray band. These substructures suggest the presence of multiple minor mergers, which are responsible for the complex dynamics of A2142, and the absence of recent or ongoing major mergers. We show that the distribution of the galaxies in the cluster core and in several substructures is consistent with the mass distribution inferred from the weak-lensing signal. Moreover, we use spatially resolved X-ray spectroscopy to measure the redshift of different regions of the intracluster medium within ∼3 arcmin from the cluster center. We find a ring of gas near the two X-ray cold fronts identified in previous analyses and measure a velocity of this ring of 810 ± 330 km s-1 larger than the cluster mean velocity. Our analysis suggests the presence of another ring surrounding the core, whose velocity is 660 ± 300 km s-1 larger than the cluster velocity. These X-ray features are not associated with any optical substructures, and support the core-sloshing scenario suggested in previous work. We dedicate this paper to the late Bepi Tormen, our beloved friend and colleague whose enthusiastic and intense work on gravitational dynamics largely contributed to our current understanding of the formation and evolution of galaxy clusters.

Late-type galaxies falling into a cluster would evolve being influenced by the interactions with both the cluster and the nearby cluster member galaxies. Most numerical studies, however, tend to focus on the effects of the former with little work done on those of the latter. We thus perform a numerical study on the evolution of a late-type galaxy interacting with neighboring early-type galaxies at high speed, using hydrodynamic simulations. Based on the information obtained from the Coma cluster, we set up the simulations for the case where a Milky Way-like late-type galaxy experiences six consecutive collisions with twice as massive early-type galaxies having hot gas in their halos at the closest approach distances of 15-65 kpc/h at the relative velocities of 1500-1600 km/s. Our simulations show that the evolution of the late-type galaxy can be significantly affected by the accumulated effects of the high-speed multiple collisions with the early-type galaxies, such as on cold gas content and star formation activity of the late-type galaxy, particularly through the hydrodynamic interactions between cold disk and hot gas halos. We find that the late-type galaxy can lose most of its cold gas after the six collisions and have more star formation activity during the collisions. By comparing our simulation results with those of galaxy-cluster interactions, we claim that the role of the galaxy-galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy-cluster interactions, depending on the dynamical history., Comment: 15 pages, 11 figures. ApJ in press