Search

Recently, the James Webb Space Telescope (JWST) has revealed a new class of high redshift (high-$z$, $z>4$) compact galaxies which are red in the rest-frame optical and blue in the rest-frame UV as V-shaped spectral energy distributions (SEDs), referred to as "Little Red Dots" (LRDs). It is very likely that LRDs host obscured broad-line active galactic nuclei (AGNs). In the meanwhile, Green pea galaxies (GPs), which are compact dwarf galaxies at low redshift, share various similar properties with high redshift star-forming galaxies. Here we aim to find the connection between the LRDs and GPs hosting broad-line AGNs (BLGPs). With a sample of 19 BLGPs obtained from our previous work, we further identify 7 GPs with V-shaped rest-frame UV-to-optical SEDs that are likely local analogs to LRDs. These V-shaped BLGPs exhibit faint UV absolute magnitudes and sub-Eddington rates similar to those of LRDs. Three of them occupy a similar region as LRDs in the BPT diagram, suggesting they have similar ionization conditions and gas-phase metallicities to LRDs. These similarities suggest that V-shaped BLGPs can be taken as local analogs of high-redshift LRDs. In addition, most (16/19) BLGPs, including 6 V-shaped BLGPs, host over-massive black holes above the local $M_{\rm BH}$-$M_{*}$ relation, making it the first sample of galaxies hosting over-massive black holes at $z<0.4$. These findings will help us learn more about the formation and co-evolution of early galaxies and black holes., Comment: 11 pages, 4 figures, 2 tables, submitted to the Astrophysical Journal Letters. Comments welcome!

In the era of large-scale astronomical surveys, fast modeling of strong lens systems has become increasingly vital. While significant progress has been made for galaxy-scale lenses, the development of automated methods for modeling larger systems, such as groups and clusters, is not as extensive. Our study aims to extend the capabilities of the GIGA-Lens code, enhancing its efficiency in modeling multi-galaxy strong lens systems. We focus on demonstrating the potential of GPU-accelerated Bayesian inference in handling complex lensing scenarios with a high number of free parameters. We employ an improved inference approach that combines image position and pixelated data with an annealing sampling technique to obtain the posterior distribution of complex models. This method allows us to overcome the challenge of limited prior information, a high number of parameters, and memory usage. Our process is exemplified through the analysis of the compact group lens system DES J0248-3955, for which we present VLT/X-shooter spectra. We measure a redshift of $z = 0.69 \pm 0.04$ for the group, and $z = 1.2722 \pm 0.0005$ for one of the extended arcs. Our enhanced method successfully constrained a lens model with 29 free parameters and lax priors in a remarkably short time. The mass of the lens is well described by a single dark-matter halo with a velocity dispersion of $\sigma_v = (690 \pm 30) \, km \, s^{-1}$. The model predicts the presence of a second source at the same redshift and a third source at approximately $z \sim 2.7$. Our study demonstrates the effectiveness of our lens modeling technique for dealing with a complex system in a short time using ground-based data. This presents considerable potential within the context of large surveys such as LSST., Comment: 10 pages, 6 figures. Submitted to A&A. The final version may differ slightly after production edits

The epoch of reionization is a landmark in structure formation and galaxy evolution. How it happened is still not clear, especially regarding which population of objects was responsible for contributing the bulk of ionizing photons toward this process. Doubly-peaked Lyman-Alpha profiles in this epoch are of particular interest since they hold information about the escape of ionizing radiation and the environment surrounding the source. We wish to understand the escape mechanisms of ionizing radiation in Lyman-Alpha emitters during this time and the origin of a doubly-peaked Lyman-alpha profile as well as estimating the size of a potential ionized bubble. Using radiative transfer models, we fit the line profile of a bright Lyman-Alpha emitter at $z\sim 6.9$ using various gas geometries. The line modeling reveals significant radiation escape from this system. While the studied source reveals significant escape ($f_{esc}$(LyA) $\sim0.8$ as predicted by the best fitting radiative transfer model) and appears to inhabit an ionized bubble of radius $R_{b}\approx 0.8^{+0.5}_{-0.3}\,pMpc\left(\frac{t_{\rm age}}{10^{8}}\right)^{\frac{1}{3}}$.Radiative transfer modeling predicts the line to be completely redwards of the systemic redshift. We suggest the line morphology is produced by inflows, multiple components emitting Ly$\alpha$, or by an absorbing component in the red wing. We propose that CDFS-1's profile holds two red peaks produced by winds within the system. Its high $f_{esc}$(Lya) and the low-velocity offset from the systemic redshift suggest that the source is an active ionizing agent. Future observations will reveal whether a peak is present bluewards of the systemic redshift or if multiple components produce the profile., Comment: 10 pages, 7 figurss

We exploit the VST ATLAS quasar/QSO catalogue to perform three measurements of the quasar halo mass profile. First, we make a new estimate of the angular auto-correlation function of $\approx230,000$ ATLAS quasars with $z_{photo}\lesssim 2.5$ and $17

We cross-correlate a low-contamination subset of the VST ATLAS g < 22.5 quasar catalogue with g < 21.5 galaxy clusters, r < 21 galaxies and r < 19.5 Luminous Red Galaxies (LRGs) to probe their halo mass profiles via quasar magnification bias caused by weak lensing. In the case of galaxy clusters we find that at small scales their mass profiles are well fitted by Navarro, Frenk and White (NFW) models with masses within the expected range. For the galaxies, we find consistency with previous SDSS-based results for the galaxy-quasar cross-correlation and the galaxy auto-correlation functions. Disagreement as to whether the cross-correlation results are in tension with $\Lambda$CDM appears due to different assumptions as to whether galaxies trace mass. We conclude that halo occupation distribution (HOD) models fit the galaxy - quasar lensing results better than models where galaxies trace the mass. We further test the cluster and galaxy HOD models in the 2-halo range using the Planck Cosmic Microwave Background (CMB) lensing map, finding that the cross-correlation with both the poorest clusters and the galaxies may be marginally over-predicted by the above HOD models. Finally, we measure the magnification bias of LRGs using both quasar and CMB lensing and find that the observed quasar lensing amplitude may be $\approx 2\times$ too high and, on larger scales, the CMB lensing amplitude may be too low to be explained by a standard LRG HOD model., Comment: 13 pages, 11 figures, accepted for publication in MNRAS

We present VLT/MUSE integral-field spectroscopy ($R\approx 1\,800$) of four giant gravitational arcs exhibiting strong C IV absorption at 8 intervening redshifts, $z_{abs}\approx 2.0$--$2.5$. We detect C IV absorption in a total of 222 adjacent and seeing-uncorrelated sightlines, whose spectra sample beams of ("de-lensed") linear size $\approx 1$ kpc. Our data show that (1) absorption velocities cluster at all probed transverse scales, $\Delta r_\perp\approx0$--$15$ kpc, depending on system; (2) the (transverse) velocity dispersion never exceeds the mean (line-of-sight) absorption spread; and (3) the (transverse) velocity autocorrelation function does not resolve kinematic patterns at the above spatial scales, but its velocity projection, $\xi^{arc}(\Delta v)$, exhibits a similar shape to the known two-point correlation function toward quasars, $\xi^{QSO}(\Delta v)$. An empirical kinematic model suggests that these results are a natural consequence of wide-beam observations of an unresolved clumpy medium. Our model recovers both the underlying velocity dispersion of the clumps ($70$--$170$ \kms) and the mean number of clumps per unit area ($2$--$13$ kpc$^{-2}$). The latter constrains the projected mean inter-clump distance to within $\approx0.3$--$0.8$ kpc, which we argue is a measure of clump size for near-unity covering fraction. The model is also able to predict $\xi^{arc}(\Delta v)$ from $\xi^{QSO}(\Delta v)$, suggesting that the strong systems that shape the former and the line-of-sight velocity components that define the latter trace the same kinematic population. Consequently, the clumps must possess an internal density structure that generates both weak and strong components. We discuss how our interpretation is consistent with previous observations using background galaxies and multiple quasars., Comment: Accepted for publication in A&A

This study aims to investigate the molecular gas content of strongly magnified low-mass star-forming galaxies around the cosmic noon period ($z\sim2$) through observations of CO emission lines and dust continuum emission, both of which serve as tracers for molecular gas. We observed twelve strongly lensed galaxies with the Atacama Compact Array to detect CO mid-j rotational transitions and dust continuum. Thanks to the strong lensing, we were able to probe the low-mass regime, previously understudied. With a compiled set of observations, we recalibrate empirical relations between star formation rate density and the CO line ratios. Using SED fitting, we derived galaxy properties and performed galaxy stacking to combine the faint signals. In all cases, molecular gas masses were estimated using both tracers. We detected CO emission in three out of 12 galaxies and dust continuum emission in three of them. The obtained molecular gas masses indicate that most of these galaxies ($\rm{M}_* < 10^{10.7}$ $\rm{M}_\odot$) have lower molecular gas fractions and shorter depletion times compared to the expectations from established scaling relations at these redshifts. Several possible explanations for this gas deficit were explored, including uncertainties in mass estimates, effects of low metallicity environments, larger atomic gas reservoirs in low-mass systems, and the possibility that these represent low-mass analogs of "main sequence starburst" galaxies, which are undergoing sustained star formation due to gas compaction despite low overall gas fractions. We conclude that there is a molecular gas deficit at these mass and metallicity regimes. Our results suggest that this deficit is likely due to a significant amount of atomic gas, which our stacking indicates is about 91% of the total gas. However, this estimation might be an upper limit in the case of our galaxies containing CO-dark gas.

We present the first results of the Hubble Deep Hydrogen Alpha (HDH$\alpha$) project, which analyzes the space-borne deep H$\alpha$ narrowband imaging data in the GOODS-S region. The HDH$\alpha$ data comprises 72 orbits' images taken with the HST ACS/WFC F658N filter. The exposure time varies across a total area of $\sim$76.1 $\rm{arcmin}^2$, adding up to a total exposure time of 195.7 ks, among which 68.8 ks are spent in the deepest region. These images are aligned, reprojected, and combined to have the same pixel grid as the Hubble Legacy Fields (HLF). The scientific goals of the HDH$\alpha$ include establishing a sample of emission-line galaxies (ELGs) including [O III] emitters at $z\sim$ 0.3, [O II] emitters at $z\sim$ 0.8, and Lyman-$\alpha$ emitters (LAEs) at $z \sim 4.4$, studying the line morphology of ELGs with high resolution imaging data, and statistically analyzing the line luminosity functions and line equivalent-width distributions of ELGs selected with HST. Furthermore, the HDH$\alpha$ project enhances the legacy value of the GOODS-S field by contributing the first HST-based narrowband image to the existing data sets, which includes the HST broadband data and other ancillary data from X-ray to radio taken by other facilities. In this paper, we describe the data reduction process of the HDH$\alpha$, select ELGs based on HST's F658N and broadband data, validate the redshifts of the selected candidates by cross matching with the public spectroscopic catalogs in the GOODS-S, and present a final catalog of the confirmed [O III] emitters at $z\sim$ 0.3, [O II] emitters at $z\sim$ 0.8, and LAEs at $z \sim 4.4$., Comment: 27 pages, 14 figures, 9 tables, accepted by ApJS

We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at $z \approx 1.703$ using VLT/MUSE IFU observations. We probe the cool outflowing gas, traced by blueshifted Mg II and Fe II absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 to 7 kpc apart within the galaxy, drive the outflows at different velocities ($V_{out} \sim $ $-161$ to $-240$ km s$^{-1}$), and mass outflow rates ($\dot{M}_{out} \sim$ 183 to 527 $M_{\odot}\ yr^{-1}$). The outflow velocities from different regions of the same galaxy vary by 80 km s$^{-1}$, which is comparable to the variation seen in a large sample of star-burst galaxies in the local Universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5 kpc$^2$-25 kpc$^2$), we find that outflow velocities vary between $ \sim $ $-120$ to $-242$ km s$^{-1}$, and the mass outflow rates vary between $\sim$ 37 to 254 $M_{\odot}\ yr^{-1}$. The outflow momentum flux in this galaxy is $\geq$ 100% of the momentum flux provided by star-formation in individual regions, and outflow energy flux is $\approx$ 10% of the total energy flux provided by star-formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution., Comment: 26 pages, 15 figures, 6 tables, accepted for publication in MNRAS, the referee comments are incorporated in this version

We present the VST ATLAS Quasar Survey, consisting of $\sim1,229,000$ quasar (QSO) candidates with $162.2$. One of the aims of this catalogue is to select QSO targets for the 4MOST Cosmology Redshift Survey. To guide our selection, we use X-ray/UV/optical/MIR data in the extended William Herschel Deep Field (WHDF) where we find a $g<22.5$ broad-line QSO density of $269\pm67$ deg$^{-2}$, roughly consistent with the expected $\sim196$ deg$^{-2}$. We also find that $\sim25$% of our QSOs are morphologically classed as optically extended. Overall, we find that in these deep data, MIR, UV and X-ray selections are all $\sim70-90$% complete while X-ray suffers less contamination than MIR and UV. MIR is however more sensitive than X-ray or UV to $z>2.2$ QSOs at $g<22.5$ and the eROSITA limit. We then adjust the selection criteria from our previous 2QDES pilot survey and prioritise VST ATLAS candidates that show both UV and MIR excess, while also selecting candidates initially classified as extended. We test our selections using data from DESI (which will be released in DR1) and 2dF to estimate the efficiency and completeness of our selections, and finally we use ANNz2 to determine photometric redshifts for the QSO candidate catalogue. Applying over the $\sim4700$ deg$^2$ ATLAS area gives us $\sim917,000$ $z<2.2$ QSO candidates of which 472,000 are likely to be $z<2.2$ QSOs, implying a sky density of $\sim$100 deg$^{-2}$, which our WHDF analysis suggests will rise to at least 130 deg$^{-2}$ when eROSITA X-ray candidates are included. At $z>2.2$, we find $\sim310,000$ candidates, of which 169,000 are likely to be QSOs for a sky density of $\sim36$ deg$^{-2}$.

We use spatially-resolved spectroscopy of a distant giant gravitational arc to test orientation effects on MgII absorption equivalent width (EW) and covering fraction (kappa) in the circumgalactic medium of a foreground star-forming galaxy (G1) at z~0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles alpha between 30 and 90 degrees (minor axis). We find an EW-D anti-correlation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and kappa with alpha, revealing a non-isotropic gas distribution. In line with our previous results on MgII kinematics suggesting the presence of outflows in G1, at minimum a simple 3-D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and alpha values probed by the arc cannot confirm the presence of a disc, but the data highly disfavor a disc alone. Our results support the interpretation that the EW-alpha correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds., Comment: Accepted in Monthly Notices of the Royal Astronomical Society

We report spectroscopic confirmations of 15 Lyman-alpha galaxies at $z\sim7$, implying a spectroscopic confirmation rate of $\sim$80% on candidates selected from LAGER (Lyman-Alpha Galaxies in the Epoch of Reionization), which is the largest (24 deg$^2$) survey aimed at finding Lyman-alpha emitters (LAEs) at $z\sim7$ using deep narrow-band imaging from DECam at CTIO. LAEs at high-redshifts are sensitive probes of cosmic reionization and narrow-band imaging is a robust and effective method for selecting a large number of LAEs. In this work, we present results from the spectroscopic follow-up of LAE candidates in two LAGER fields, COSMOS and WIDE-12, using observations from Keck/LRIS. We report the successful detection of Ly$\alpha$ emission in 15 candidates (11 in COSMOS and 4 in WIDE-12 fields). Three of these in COSMOS have matching confirmations from a previous LAGER spectroscopic follow-up and are part of the overdense region, LAGER-$z7$OD1. Additionally, two candidates that were not detected in the LRIS observations have prior spectroscopic confirmations from Magellan. Including these, we obtain a spectroscopic confirmation success rate of $\sim$$80$% for LAGER LAE candidates. Apart from Ly$\alpha$, we do not detect any other UV nebular lines in our LRIS spectra; however, we estimate a 2$\sigma$ upper limit for the ratio of NV/Ly$\alpha$, $f_{NV}/f_{Ly\alpha} \lesssim 0.27$, which implies that ionizing emission from these sources is mostly dominated by star formation. Including confirmations from this work, a total of 33 LAE sources from LAGER are now spectroscopically confirmed. LAGER has more than doubled the sample of spectroscopically confirmed LAE sources at $z\sim7$., Comment: 8 pages, 4 figures; Submitted to ApJ

We image the spatial extent of a cool galactic outflow with fine structure Fe II$^*$ emission and resonant Mg II emission in a gravitationally lensed star-forming galaxy at $z = 1.70347$. The Fe II$^*$ and Mg II (continuum-subtracted) emissions span out to radial distances of $\sim$14.33 kpc and 26.5 kpc, respectively, with maximum spatial extents of $\sim$21 kpc for Fe II$^*$ emission and $\sim$30 kpc for Mg II emission. Mg II residual emission is patchy and covers a total area of $\sim$184 kpc$^2$, constraining the minimum area covered by the outflowing gas to be $\sim$13% of the total area. Mg II emission is asymmetric and shows $\sim$21% more extended emission along the declination direction. We constrain the covering fractions of the Fe II$^*$ and Mg II emission as a function of radial distance and characterize them with a power law model. The Mg II 2803 emission line shows two kinematically distinct emission components, and may correspond to two distinct shells of outflowing gas with a velocity separation of $\Delta v \sim$ 400 km/s. By using multiple images with different magnifications of the galaxy in the image plane, we trace the Fe II$^*$, Mg II emissions around three individual star-forming regions. In all cases, both the Fe II$^*$ and Mg II emissions are more spatially extended compared to the star forming regions traced by the [O II] emission. These findings provide robust constraints on the spatial extent of the outflowing gas, and combined with outflow velocity and column density measurements will give stringent constraints on mass outflow rates of the galaxy., Comment: 22 pages, 14 figures, 4 tables, accepted to ApJ, the referee comments are incorporated in this version

Star-forming galaxies (SFGs) with stellar masses below $10^{10}\,M_\odot$ make up the bulk of the galaxy population at $z>2$. The properties of the cold gas in these galaxies can only be probed in very deep ALMA observations or by targeting strongly lensed galaxies. Here we report the results of a pilot survey using the Atacama Compact Array (ACA) of molecular gas in the most strongly magnified galaxies selected as giant arcs in optical data. The selection in rest-frame UV wavelengths ensures that sources are regular star forming galaxies, without a priori indications of intense dusty starburst activity. We conducted Band 4 and Band 7 observations to detect mid-$J$ CO, [C I] and thermal continuum as molecular gas tracers from four strongly lensed systems at $z\approx2-3$: our targets are SGAS J1226651.3+215220 (A and B), SGAS J003341.5+024217 and the Sunburst Arc. The measured molecular mass is then projected onto the source plane with detailed lens models developed from high resolution HST observations. Multiwavelength photometry is then used to obtain the intrinsic stellar mass and star formation rate via SED fitting. In only one of the sources are the three tracers robustly detected, while in the others they are either undetected or detected in continuum only. The implied molecular gass masses range from $4\times 10^{9}\,M_\odot$ in the detected source to an upper limit of $\lesssim 10^9\,M_\odot$ in the most magnified source. The inferred gas fraction and gas depletion timescale are found to lie approximately 0.5 to 1.0 dex below the established scaling relations based on previous studies of unlensed massive galaxies. Our results indicate that the cold gas content of intermediate to low mass galaxies should not be extrapolated from the trends seen in more massive high-$z$ galaxies. (Abridged abstract), Comment: 17 pages, 7 figures. Accepted for publication in Astronomy & Astrophysics

We present a new measurement of the Ly$\alpha$ luminosity function at redshift $z=6.9$, finding moderate evolution from $z=5.7$ that is consistent with a fully or largely ionized $z\sim7$ intergalactic medium. Our result is based on four fields of the LAGER (Lyman Alpha Galaxies in the Epoch of Reionization) project. Our survey volume of $6.1\times10^{6}$ Mpc$^{3}$ is double that of the next largest $z\sim 7$ survey. We combine two new LAGER fields (WIDE12 and GAMA15A) with two previously reported LAGER fields (COSMOS and CDFS). In the new fields, we identify $N=95$ new $z=6.9$ Ly$\alpha$ emitters (LAEs); characterize our survey's completeness and reliability; and compute Ly$\alpha$ luminosity functions. The best-fit Schechter luminosity function parameters for all four LAGER fields are in good general agreement. Two fields (COSMOS and WIDE12) show evidence for a bright-end excess above the Schechter function fit. We find that the Ly$\alpha$ luminosity density declines at the same rate as the UV continuum LF from $z=5.7$ to $z=6.9$. This is consistent with an intergalactic medium that was fully ionized as early as redshift $z\sim 7$, or with a volume-averaged neutral hydrogen fraction of $x_{HI} < 0.33$ at $1\sigma$., Comment: 19 pages, 11 figures; accepted by ApJ

The H$\alpha$ equivalent width (EW) is an observational proxy for specific star formation rate (sSFR) and a tracer of episodic star-formation activity. Previous assessments show that EW strongly anti-correlates with stellar mass as $M^{-0.25}$ similar to the sSFR -- stellar mass relation. However, such a correlation may be driven/formed by selection effects. In this study, we investigate how H$\alpha$ EWs correlate with galaxy properties and how selection biases could alter such correlations using a $z = 0.47$ narrowband-selected sample of 1572 H$\alpha$ emitters from the Ly$\alpha$ Galaxies in the Epoch of Reionization (LAGER) survey. The sample covers 3 deg$^2$ of COSMOS and $1.1\times10^5$ cMpc$^3$. We assume an intrinsic EW distribution to form mock samples of H$\alpha$ emitters (HAEs) and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find EW intrinsically correlates with stellar mass as $W_0 \propto M^{-0.16\pm0.03}$ and decreases by a factor of $\sim 3$ from $10^{7}$ to $10^{10}$ M$_\odot$. We find low-mass HAEs to be $\sim 320$ times more likely to have rest-frame EW$ > 200$\AA compared to high-mass HAEs. Combining the intrinsic EW -- stellar mass correlation with an observed SMF correctly reproduces the observed H$\alpha$ LF, while not correcting for selection effects underestimates the number of bright HAEs. This suggests that the intrinsic EW -- stellar mass correlation is physically significant and reproduces three statistical distributions of galaxy populations (LF, SMF, EW distribution). At lower masses, we find there are more high-EW outliers compared to high masses, even after taking into account selection effects. Our results suggest that high sSFR outliers indicative of bursty SF activity are intrinsically more prevalent in low-mass HAEs and not a byproduct of selection effects., Comment: 21 Pages, 13 Figures, 2 Tables, accepted to MNRAS

Protoclusters, the progenitors of the most massive structures in the Universe, have been identified at redshifts of up to 6.6. Besides exploring early structure formation, searching for protoclusters at even higher redshifts is particularly useful to probe the reionization. Here we report the discovery of the protocluster LAGER-z7OD1 at a redshift of 6.93, when the Universe was only 770 million years old and could be experiencing rapid evolution of the neutral hydrogen fraction in the intergalactic medium. The protocluster is identified by an overdensity of 6 times the average galaxy density, and with 21 narrowband selected Lyman-$\alpha$ galaxies, among which 16 have been spectroscopically confirmed. At redshifts similar to or above this record, smaller protogroups with fewer members have been reported. LAGER-z7OD1 shows an elongated shape and consists of two subprotoclusters, which would have merged into one massive cluster with a present-day mass of $3.7 \times 10^{15}$ solar masses. The total volume of the ionized bubbles generated by its member galaxies is found to be comparable to the volume of the protocluster itself, indicating that we are witnessing the merging of the individual bubbles and that the intergalactic medium within the protocluster is almost fully ionized. LAGER-z7OD1 thus provides a unique natural laboratory to investigate the reionization process., Comment: 9 pages, 5 figures, and 1 table. Accepted by Nature Astronomy

We present our measurements of the H$\alpha$, [OIII], and [OII] luminosity functions as part of the Lyman Alpha Galaxies at Epoch of Reionization (LAGER) survey using our samples of 1577 $z = 0.47$ H$\alpha$-, 3933 $z = 0.93$ [OIII]-, and 5367 $z = 1.59$ [OII]-selected emission line galaxies in a single 3 deg$^2$ CTIO/Blanco DECam pointing of the COSMOS field. Our observations reach 5$\sigma$ depths of $8.2\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ and comoving volumes of $(1-7)\times10^{5}$ Mpc$^3$ making our survey one of the deepest narrowband surveys. We measure the observed luminosity functions and find best-fits of $\phi^\star = 10^{-3.16\pm0.09}$ Mpc$^{-3}$ and $L^\star = 10^{41.72\pm0.09}$ erg s$^{-1}$ for H$\alpha$, $\phi^\star = 10^{-2.16^{+0.10}_{-0.12}}$ Mpc$^{-3}$ and $L^\star = 10^{41.38^{+0.07}_{-0.06}}$ erg s$^{-1}$ for [OIII], and $\phi^\star = 10^{-1.97^{+0.07}_{-0.07}}$ Mpc$^{-3}$ and $L^\star = 10^{41.66\pm0.03}$ erg s$^{-1}$ for [OII], with $\alpha$ fixed to $-1.75$, $-1.6$, and $-1.3$, respectively. An excess of bright $> 10^{42}$ erg s$^{-1}$ [OIII] emitters is observed and may be due to AGN contamination. Dust corrections are applied assuming $A_{\rm{H}\alpha} = 1$ mag. We also design our own empirical rest-frame $g - r$ calibration using SDSS DR12 data, test it against our $z = 0.47$ H$\alpha$ emitters with $z$COSMOS $1$D spectra, and calibrate it for $(g - r)$ between $-0.8$ and $1.3$ mag. Dust and AGN-corrected star formation rate densities (SFRDs) are measured as $\log_{10}\rho_{\rm{SFR}}/(\rm{M}_\odot\ \rm{yr}^{-1}\ \rm{Mpc}^{-3}) = -1.63\pm0.04$, $-1.07\pm0.06$, and $-0.90\pm0.10$ for H$\alpha$, [OIII], and [OII], respectively. We find our [OIII] and [OII] samples fully trace cosmic star formation activity at their respective redshifts in comparison to multi-wavelength SFRDs, while the H$\alpha$ sample traces $\sim 70$ percent of the total $z = 0.47$ SFRD., Comment: 21 pages, 12 figures, 6 Tables. Accepted by MNRAS for publication on 6 Jan 2020

We present spatially-resolved echelle spectroscopy of an intervening MgII-FeII-MgI absorption-line system detected at $z_{\rm abs}=0.73379$ toward the giant gravitational arc PSZ1 G311.65-18.48. The absorbing gas is associated to an inclined disk-like star-forming galaxy, whose major axis is aligned with the two arc-segments reported here. We probe in absorption the galaxy's extended disk continuously, at $\approx 3$ kpc sampling, from its inner region out to $15\times$ the optical radius. We detect strong ($W_0^{2796}>0.3$ \r{A}) coherent absorption along $13$ independent positions at impact parameters $D=0$--$29$ kpc on one side of the galaxy, and no absorption at $D=28$--$57$ kpc on the opposite side (all de-lensed distances at $z_{\rm abs}$). We show that: (1) the gas distribution is anisotropic; (2) $W_0^{2796}$, $W_0^{2600}$, $W_0^{2852}$, and the ratio $W_0^{2600}\!/W_0^{2796}$, all anti-correlate with $D$; (3) the $W_0^{2796}$-$D$ relation is not cuspy and exhibits significantly less scatter than the quasar-absorber statistics; (4) the absorbing gas is co-rotating with the galaxy out to $D \lesssim 20$ kpc, resembling a `flat' rotation curve, but at $D\gtrsim 20$ kpc velocities decline below the expectations from a 3D disk-model extrapolated from the nebular [OII] emission. These signatures constitute unambiguous evidence for rotating extra-planar diffuse gas, possibly also undergoing enriched accretion at its edge. Arguably, we are witnessing some of the long-sought processes of the baryon cycle in a single distant galaxy expected to be representative of such phenomena., Comment: Accepted for publication in MNRAS

The strong observed clustering of $z>3.5$ quasars indicates they are hosted by massive ($M_{\rm{halo}}\gtrsim10^{12}\,h^{-1}\,\rm{M_{\odot}}$) dark matter halos. Assuming quasars and galaxies trace the same large-scale structures, this should also manifest as strong clustering of galaxies around quasars. Previous work on high-redshift quasar environments, mostly focused at $z>5$, have failed to find convincing evidence for these overdensities. Here we conduct a survey for Lyman alpha emitters (LAEs) in the environs of 17 quasars at $z\sim4$ probing scales of $R\lesssim7\,h^{-1}\,{\rm{Mpc}}$. We measure an average LAE overdensity around quasars of 1.4 for our full sample, which we quantify by fitting the quasar-LAE cross-correlation function. We find consistency with a power-law shape with correlation length of $r^{QG}_{0}=2.78^{+1.16}_{-1.05}\,h^{-1}\,{\rm{cMpc}}$ for a fixed slope of $\gamma=1.8$. We also measure the LAE auto-correlation length and find $r^{GG}_{0}=9.12^{+1.32}_{-1.31}\,h^{-1}$\,cMpc ($\gamma=1.8$), which is $3.3$ times higher than the value measured in blank fields. Taken together our results clearly indicate that LAEs are significantly clustered around $z\sim4$ quasars. We compare the observed clustering with the expectation from a deterministic bias model, whereby LAEs and quasars probe the same underlying dark matter overdensities, and find that our measurements fall short of the predicted overdensities by a factor of 2.1. We discuss possible explanations for this discrepancy including large-scale quenching or the presence of excess dust in galaxies near quasars. Finally, the large cosmic variance from field-to-field observed in our sample (10/17 fields are actually underdense) cautions one from over-interpreting studies of $z\sim6$ quasar environments based on a single or handful of quasar fields., Comment: 19 pages, 12 figures, submitted to the ApJ

We present the first spatially resolved analysis of rest-frame optical and UV imaging and spectroscopy for a lensed galaxy at z = 2.39 hosting a Seyfert active galactic nucleus (AGN). Proximity to a natural guide star has enabled high signal-to-noise VLT SINFONI + adaptive optics observations of rest-frame optical diagnostic emission lines, which exhibit an underlying broad component with FWHM ~ 700 km/s in both the Balmer and forbidden lines. Measured line ratios place the outflow robustly in the region of the ionization diagnostic diagrams associated with AGN. This unique opportunity - combining gravitational lensing, AO guiding, redshift, and AGN activity - allows for a magnified view of two main tracers of the physical conditions and structure of the interstellar medium in a star-forming galaxy hosting a weak AGN at cosmic noon. By analyzing the spatial extent and morphology of the Ly-alpha and dust-corrected H-alpha emission, disentangling the effects of star formation and AGN ionization on each tracer, and comparing the AGN induced mass outflow rate to the host star formation rate, we find that the AGN does not significantly impact the star formation within its host galaxy., Comment: 16 pages, 5 figures, accepted for publication in ApJ

We present the largest-ever sample of 79 Ly$\alpha$ emitters (LAEs) at $z\sim$ 7.0 selected in the COSMOS and CDFS fields of the LAGER project (the Lyman Alpha Galaxies in the Epoch of Reionization). Our newly amassed ultradeep narrowband exposure and deeper/wider broadband images have more than doubled the number of LAEs in COSMOS, and we have selected 30 LAEs in the second field CDFS. We detect two large-scale LAE-overdense regions in the COSMOS that are likely protoclusters at the highest redshift to date. We perform injection and recovery simulations to derive the sample incompleteness. We show significant incompleteness comes from blending with foreground sources, which however has not been corrected in LAE luminosity functions in {the} literature. The bright end bump in the Ly$\alpha$ luminosity function in COSMOS is confirmed with 6 (2 newly selected) luminous LAEs (L$_{Ly\alpha}$ $>$ 10$^{43.3}$ erg s$^{-1}$). Interestingly, the bump is absent in CDFS, in which only one luminous LAE is detected. Meanwhile, the faint end luminosity functions from the two fields well agree with each other. The 6 luminous LAEs in COSMOS coincide with 2 LAE-overdense regions, while such regions are not seen in CDFS. The bright-end luminosity function bump could be attributed to ionized bubbles in a patchy reionization. It appears associated with cosmic overdensities, thus supports an inside-out reionization topology at $z$ $\sim$ 7.0, i.e., the high density peaks were ionized earlier compared to the voids. An average neutral hydrogen fraction of $x_{HI}$ $\sim$ 0.2 -- 0.4 is derived at $z\sim$ 7.0 based on the cosmic evolution of the Ly$\alpha$ luminosity function., Comment: 23 pages, 11 figures, 2 tables, accepted for publication in ApJ

We present the design for the first narrowband filter NB964 for the Dark Energy Camera (DECam), which is operated on the 4m Blanco Telescope at the Cerro Tololo Inter-American Observatory. The NB964 filter profile is essentially defined by maximizing the power of searching for Lyman alpha emitting galaxies (LAEs) in the epoch of reionization, with the consideration of the night sky background in the near-infrared and the DECam quantum efficiency. The NB964 filter was manufactured by Materion in 2015. It has a central wavelength of 964.2 nm and a full width at half maximum (FWHM) of 9.2 nm. An NB964 survey named LAGER (Lyman Alpha Galaxies in the Epoch of Reionization) has been ongoing since December 2015. Here we report results of lab tests, on-site tests and observations with the NB964 filter. The excellent performances of this filter ensure that the LAGER project is able to detect LAEs at z~7 with a high efficiency., Comment: 12 pages, 12 figures, submitted to PASP

We report on newly identified galaxy clusters from the high signal-to-noise ($>5$-$\sigma$) end of the second all-sky \textit{Planck} Sunyaev-Zel'dovich (SZ) catalog (PSZ2). The clusters are identified in deep, optical imaging from the Kitt Peak National Observatory 4m Mayall telescope taken between 2014 and 2017. Here we focus on the highest richness systems, and identify galaxy clusters through a combination of the maxBCG algorithm and visual image inspection. Galaxy clusters are considered to be confirmed if they are both rich and spatially coincident ($\lesssim 6'$) with the reported PSZ2 position. Of the 85 fields containing unconfirmed PSZ2 candidates observed, we find 15 (17.6% of the observed sample) corresponding galaxy clusters ($ 0.13 < z < 0.78$), 12 of which are previously unrecognized as counterparts. To explain this low identification fraction, we consider three possible scenarios: that clusters are (1) mostly at low-z, (2) mostly at high-z, or (3) located in fields with high object density. None of these scenarios alone can account for the low purity of rich galaxy clusters among the high signal-to-noise PSZ2 unconfirmed candidates., Comment: 14 pages, 8 Figures, Accepted by ApJ

Cosmological simulations predict that a significant fraction of the low-$z$ baryon budget resides in large-scale filaments in the form of a diffuse plasma at temperatures $T \sim 10^{5} - 10^{7}$ K. However, direct observation of this so-called warm-hot intergalactic medium (WHIM) has been elusive. In the $\Lambda$CDM paradigm, galaxy clusters correspond to the nodes of the cosmic web at the intersection of several large-scale filamentary threads. In previous work, we used HST/COS data to conduct the first survey of broad HI Ly$\alpha$ absorbers (BLAs) potentially produced by WHIM in inter-cluster filaments. We targeted a single QSO, namely Q1410, whose sight-line intersects $7$ independent inter-cluster axes at impact parameters $<3$ Mpc (co-moving), and found a tentative excess of a factor of ${\sim}4$ with respect to the field. Here, we further investigate the origin of these BLAs by performing a blind galaxy survey within the Q1410 field using VLT/MUSE. We identified $77$ sources and obtained the redshifts for $52$ of them. Out of the total sample of $7$ BLAs in inter-cluster axes, we found $3$ without any galaxy counterpart to stringent luminosity limits ($\sim 4 \times 10^{8}$ L$_{\odot}$ ${\sim} 0.01$ L$_{*}$), providing further evidence that these BLAs may represent genuine WHIM detections. We combined this sample with other suitable BLAs from the literature and inferred the corresponding baryon mean density for these filaments in the range $\Omega^{\rm fil}_{\rm bar}= 0.02-0.04$. Our rough estimates are consistent with the predictions from numerical simulations but still subject to large systematic uncertainties, mostly from the adopted geometry, ionization corrections and density profile., Comment: Accepted in MNRAS

Every star-forming galaxy has a halo of metal-enriched gas extending out to at least 100 kpc, as revealed by the absorption lines this gas imprints on the spectra of background quasars. However, quasars are sparse and typically probe only one narrow pencil beam through the intervening galaxy. Close quasar pairs and gravitationally lensed quasars have been used to circumvent this inherently one-dimensional technique, but these objects are rare and the structure of the circum-galactic medium remains poorly constrained. As a result, our understanding of the physical processes that drive the re-cycling of baryons across the lifetime of a galaxy is limited. Here we report integral-field (tomographic) spectroscopy of an extended background source -a bright giant gravitational arc. We can thus coherently map the spatial and kinematic distribution of Mg II absorption -a standard tracer of enriched gas- in an intervening galaxy system at redshift 0.98 (i.e., ~8 Gyr ago). Our gravitational-arc tomography unveils a clumpy medium in which the absorption-strength decreases with increasing impact parameter, in good agreement with the statistics towards quasars; furthermore, we find strong evidence that the gas is not distributed isotropically. Interestingly, we detect little kinematic variation over a projected area of ~600 kpc squared, with all line-of-sight velocities confined to within a few tens of km/s of each other. These results suggest that the detected absorption originates from entrained recycled material, rather than in a galactic outflow., Comment: Published online in Nature on 31 January 2018

We present Atacama Large Millimeter/submillimeter Array observations of CO lines and dust continuum emission of the source RCSGA 032727--132609, a young $z=1.7$ low-metallicity starburst galaxy. The CO(3-2) and CO(6-5) lines, and continuum at rest-frame $450\,\mu m$ are detected and show a resolved structure in the image plane. We use the corresponding lensing model to obtain a source plane reconstruction of the detected emissions revealing intrinsic flux density of $S_{450\,\mu m}=23.5_{-8.1}^{+26.8}$ $\mu$Jy and intrinsic CO luminosities $L'_{\rm CO(3-2)}=2.90_{-0.23}^{+0.21}\times10^{8}$ ${\rm K\,km\,s^{-1}\,pc^{2}}$ and $L'_{\rm CO(6-5)}=8.0_{-1.3}^{+1.4}\times10^{7}$ ${\rm K\,km\,s^{-1}\,pc^{2}}$. We used the resolved properties in the source plane to obtain molecular gas and star-formation rate surface densities of $\Sigma_{\rm H2}=16.2_{-3.5}^{+5.8}\,{\rm M}_{\odot}\,{\rm pc}^{-2}$ and $\Sigma_{\rm SFR}=0.54_{-0.27}^{+0.89}\,{\rm M}_{\odot}\,{\rm yr}^{-1}\,{\rm kpc}^{-2}$ respectively. The intrinsic properties of RCSGA 032727--132609 show an enhanced star-formation activity compared to local spiral galaxies with similar molecular gas densities, supporting the ongoing merger-starburst phase scenario. RCSGA 032727--132609 also appears to be a low--density starburst galaxy similar to local blue compact dwarf galaxies, which have been suggested as local analogs to high-redshift low-metallicity starburst systems. Finally, the CO excitation level in the galaxy is consistent with having the peak at ${\rm J}\sim5$, with a higher excitation concentrated in the star-forming clumps., Comment: 11 pages, 4 figures, accepted for publication in ApJL

The Large Synoptic Survey Telescope (LSST) will enable revolutionary studies of galaxies, dark matter, and black holes over cosmic time. The LSST Galaxies Science Collaboration has identified a host of preparatory research tasks required to leverage fully the LSST dataset for extragalactic science beyond the study of dark energy. This Galaxies Science Roadmap provides a brief introduction to critical extragalactic science to be conducted ahead of LSST operations, and a detailed list of preparatory science tasks including the motivation, activities, and deliverables associated with each. The Galaxies Science Roadmap will serve as a guiding document for researchers interested in conducting extragalactic science in anticipation of the forthcoming LSST era., Comment: For more information, see https://galaxies.science.lsst.org

The study of galaxy morphology is fundamental to understand the physical processes driving the structural evolution of galaxies. It has long been known that dense environments host high fractions of early-type galaxies and low fractions of late-type galaxies, indicating that the environment affects the structural evolution of galaxies. In this paper we present an analysis of the morphological composition of red sequence galaxies in a sample of 9 galaxy clusters at $0.8

[abridged] The Hubble and Spitzer Space Telescope surveys of the Frontier Fields (FF) provide extremely deep images around six massive, strong-lensing clusters of galaxies. The ALMA FF survey aims to cover the same fields at 1.1mm, with maps reaching (unlensed) sensitivities of $<$70$\mu$Jy, in order to explore the properties of background dusty star-forming galaxies. We report on the multi-wavelength photometric analysis of all 12 significantly detected ($>$5$\sigma$) sources in the first three FF clusters observed by ALMA, based on data from Hubble and Spitzer, the VLT and Herschel. We measure the total photometry in all available bands and determine the photometric redshifts and the physical properties of the counterparts via SED-fitting. In particular, we carefully estimate the FIR photometry using 1.1mm priors to limit the misidentification of blended FIR counterparts, which strongly affect some flux estimates in previous FIR catalogs. We identify robust near-infrared (NIR) counterparts for all 11 sources with K$_s$ detection, the majority of which are quite red, with eight having $F814W-K_s\gtrsim 4$ and five having $F160W-[4.5]\gtrsim3$. From the FIR point of view, all our objects have $z_{phot}$$\sim$1--3, whereas based on the optical SED one object prefers a high-$z$ solution ($z\geq\ $7). Five objects among our sample have spectroscopic redshifts from the GLASS survey for which we can reproduce their SEDs with existing templates. This verification confirms the validity of our photometric redshift methodology. The mean redshift of our sample is $z_{phot}$=1.99$\pm$0.27. All 1.1mm selected objects are massive (10.0$<\log[M_{\star}(M_{\odot})]<$ 11.5), with high star formation rates ($<\log[SFR(M_{\odot}/yr)]> \approx$1.6) and high dust contents (8.1 $<\log[M_{dust} (M_{\odot})]<$8.8), consistent with previous ALMA surveys., Comment: 18 pages, 11 figures, accepted for publication in A&A

Narrowband imaging is a highly successful approach for finding large numbers of high redshift Lya emitting galaxies (LAEs) up to z~6.6. However, at z>~7 there are as yet only 3 narrowband selected LAEs with spectroscopic confirmations (two at z~6.9-7.0, one at z~7.3), which hinders extensive studies on cosmic reionization and galaxy evolution at this key epoch. We have selected 23 candidate z~6.9 LAEs in COSMOS field with the large area narrowband survey LAGER (Lyman-Alpha Galaxies at the End of Reionization). In this work we present spectroscopic followup observations of 12 candidates using IMACS on Magellan. For 9 of these, the observations are sufficiently deep to detect the expected lines. Lya emission lines are identified in six sources (yielding a success rate of 2/3), including 3 luminous LAEs with Lya luminosities of L(Lya) ~ 10^{43.5} erg/s, the highest among known spectroscopically confirmed galaxies at >~7.0. This triples the sample size of spectroscopically confirmed narrowband selected LAEs at z>~7, and confirms the bright end bump in the Lya luminosity function we previously derived based on the photometric sample, supporting a patchy reionization scenario. Two luminous LAEs appear physically linked with projected distance of 1.1 pMpc and velocity difference of ~ 170 km/s. They likely sit in a common ionized bubble produced by themselves or with close neighbors, which reduces the IGM attenuation of Lya. A tentative narrow NV${\lambda}$1240 line is seen in one source, hinting at activity of a central massive black hole with metal rich line emitting gas., Comment: 6 pages, 3 figures, 2 tables, accepted by ApJL

We present the first results from the ongoing LAGER project (Lyman Alpha Galaxies in the Epoch of Reionization), which is the largest narrowband survey for $z \sim$ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark-Energy Camera (DECam) on the NOAO/CTIO 4m Blanco telescope, LAGER has collected 34 hours NB964 narrowband imaging data in the 3 deg$^2$ COSMOS field. We have identified 23 Lyman Alpha Emitter (LAE) candidates at $z$ = 6.9 in the central 2-deg$^2$ region, where DECam and public COSMOS multi-band images exist. The resulting luminosity function can be described as a Schechter function modified by a significant excess at the bright end (4 galaxies with $L_{Ly\alpha} \sim $ 10$^{43.4\pm0.2}$ erg s$^{-1}$). The number density at $L_{Ly\alpha}\sim$ 10$^{43.4\pm0.2}$ erg s$^{-1}$ is little changed from z= 6.6, while at fainter $L_{Ly\alpha}$ it is substantially reduced. Overall, we see a fourfold reduction in Ly$\alpha$ luminosity density from $z$ = 5.7 to 6.9. Combined with a more modest evolution of the continuum UV luminosity density, this suggests a factor of $\sim 3$ suppression of Ly$\alpha$ by radiative transfer through the $z \sim$ 7 intergalactic medium (IGM). It indicates an IGM neutral fraction $x_{HI}$ $\sim$ 0.4--0.6 (assuming Ly$\alpha$ velocity offsets of 100-200 km s$^{-1}$). The changing shape of the Ly$\alpha$ luminosity function between $z\lesssim 6.6$ and $z=6.9$ supports the hypothesis of ionized bubbles in a patchy reionization at $z\sim$ 7., Comment: 7 pages, 3 figures (updated), 2 tables (updated), Accepted for publication in ApJ Letters

In the standard picture of structure formation, the first massive galaxies are expected to form at the highest peaks of the density field, which constitute the cores of massive proto-clusters. Luminous quasars (QSOs) at z~4 are the most strongly clustered population known, and should thus reside in massive dark matter halos surrounded by large overdensities of galaxies, implying a strong QSO-galaxy cross-correlation function. We observed six z~4 QSO fields with VLT/FORS exploiting a novel set of narrow band filters custom designed to select Lyman Break Galaxies (LBGs) in a thin redshift slice of Delta_z~0.3, mitigating the projection effects that have limited the sensitivity of previous searches for galaxies around z>~4 QSOs. We find that LBGs are strongly clustered around QSOs, and present the first measurement of the QSO-LBG cross-correlation function at z~4, on scales of 0.1<~R<~9 Mpc/h (comoving). Assuming a power law form for the cross-correlation function xi=(r/r0_QG)^gamma, we measure r0_QG=8.83^{+1.39}_{-1.51} Mpc/h for a fixed slope of gamma=2.0. This result is in agreement with the expected cross-correlation length deduced from measurements of the QSO and LBG auto-correlation function, and assuming a linear bias model. We also measure a strong auto-correlation of LBGs in our QSO fields finding r0_GG=21.59^{+1.72}_{-1.69} Mpc/h for a fixed slope of gamma=1.5, which is ~4 times larger than the LBG auto-correlation length in random fields, providing further evidence that QSOs reside in overdensities of LBGs. Our results qualitatively support a picture where luminous QSOs inhabit exceptionally massive (M_halo>10^12 M_sun) dark matter halos at z~4., Comment: 25 pages, 22 figures, submitted to the ApJ

We present an extensive spectroscopic follow-up campaign of 29 strong lensing (SL) selected galaxy clusters discovered primarily in the Second Red-Sequence Cluster Survey (RCS-2). Our spectroscopic analysis yields redshifts for 52 gravitational arcs present in the core of our galaxy clusters, which correspond to 35 distinct background sources that are clearly distorted by the gravitational potential of these clusters. These lensed galaxies span a wide redshift range of $0.8 \le z \le 2.9$, with a median redshift of $z_s = 1.8 \pm 0.1 $. We also measure reliable redshifts for 1004 cluster members, allowing us to obtain robust velocity dispersion measurements for 23 of these clusters, which we then use to determine their dynamical masses by using a simulation-based $\sigma_{DM} - M_{200}$ scaling relation. The redshift and mass ranges covered by our SL sample are $0.22 \le z \le 1.01$ and $5 \times10^{13} \le M_{200}/h^{-1}_{70}M_{\odot} \le 1.9\times10^{15}$, respectively. We analyze and quantify some possible effects that might bias our mass estimates, such as the presence of substructure, the region where cluster members are selected for spectroscopic follow-up, the final number of confirmed members, and line-of-sight effects. We find that 10 clusters of our sample with $N_{mem} \gtrsim 20$ show signs of dynamical substructure. However, the velocity data of only one system is inconsistent with a uni-modal distribution. We therefore assume that the substructures are only marginal and not of comparable size to the clusters themselves. Consequently, our velocity dispersion and mass estimates can be used as priors for SL mass reconstruction studies and also represent an important step toward a better understanding of the properties of the SL galaxy cluster population., Comment: Accepted for publication in ApJ

We analyse the evolution of the red sequence in a sample of galaxy clusters at redshifts $0.8 11.5$) red sequence galaxies in the WINGS clusters, which do not include only the brightest cluster galaxies and which are not present in the HCS clusters, suggesting that they formed at epochs later than $z=0.8$. The comparison with the luminosity distribution of a sample of passive red sequence galaxies drawn from the COSMOS/UltraVISTA field in the photometric redshift range $0.8

We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using \Nbody\ simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses $M_{200}$ are in the range $(1-15)\times10^{14}M_\odot$. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of $1.10\pm0.13$, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales., Comment: Accepted for publication in MNRAS. Updated discussion, conclusions unchanged. 16 pages, 10 figures, 4 tables in main text plus 2 pages, 4 figures and 1 table in appendices

We present an initial study of the mass and evolutionary state of a massive and distant cluster, RCS2 J232727.6-020437. This cluster, at z=0.6986, is the richest cluster discovered in the RCS2 project. The mass measurements presented in this paper are derived from all possible mass proxies: X-ray measurements, weak-lensing shear, strong lensing, Sunyaev Zel'dovich effect decrement, the velocity distribution of cluster member galaxies, and galaxy richness. While each of these observables probe the mass of the cluster at a different radius, they all indicate that RCS2 J232727.6-020437 is among the most massive clusters at this redshift, with an estimated mass of M_200 ~3 x10^15 h^-1 Msun. In this paper, we demonstrate that the various observables are all reasonably consistent with each other to within their uncertainties. RCS2 J232727.6-020437 appears to be well relaxed -- with circular and concentric X-ray isophotes, with a cool core, and no indication of significant substructure in extensive galaxy velocity data., Comment: 19 pages, 15 figures, submitted to ApJ on March 5, 2015; in press. Manuscript revised following the referee review