- ID:
- ivo://CDS.VizieR/J/ApJ/859/52
- Title:
- NGFS. III. Dwarf galaxies in outer regions
- Short Name:
- J/ApJ/859/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 271 previously undetected dwarf galaxies in the outer Fornax cluster regions at radii r_vir_/4<r<r_vir_/2 using data from the Next Generation Fornax Survey (NGFS) with deep coadded u', g', and i' images obtained with Blanco/DECam at Cerro Tololo Interamerican Observatory. From the 271 dwarf candidates, we find 39 to be nucleated. Together with our previous study of the central Fornax region, the new dwarfs detected with NGFS data number 392, of which 56 are nucleated. The total Fornax dwarf galaxy population from NGFS and other catalogs rises, therefore, to a total of 643 with 181 being nucleated, yielding an overall nucleation fraction of 28%. The absolute i'-band magnitudes for the outer NGFS dwarfs are in the range -18.80<=M_i'_<=-8.78 with effective radii r_eff,i'_=0.18-2.22kpc and an average Sersic index <n>_i'_=0.81. Nonnucleated dwarfs are found to be fainter and smaller by {Delta}<M_i'_>=2.25mag and {Delta}<r_eff,i'_>=0.4kpc than the nucleated dwarfs. We demonstrate a significant clustering of dwarf galaxies on scales <~100kpc, and projected surface number density profile estimates, {Sigma}_N_(r), show a concentration of dwarfs in the Fornax core region within r<~350kpc. {Sigma}_N_(r) has a flat distribution up to ~350kpc, beyond which it declines for the nonnucleated dwarfs. The nucleated dwarfs have a steeper {Sigma}N(r) distribution, are more concentrated toward NGC 1399, and are decreasing rapidly outwards. This is the first time the transition from cluster to field environment has been established for the very faint dwarf galaxy population with robust sample statistics.
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- ID:
- ivo://CDS.VizieR/J/A+A/650/A99
- Title:
- NGVS 3543 images at 8 wavelengths
- Short Name:
- J/A+A/650/A99
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The interaction of galaxies with their environment plays an important role in their evolution. Ultra-diffuse galaxies (UDGs) have been found in large numbers in clusters. We detected a few star forming blobs in the VESTIGE survey, located at ~5kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction of this low surface brightness system with the surrounding cluster environment. We use a complete set of multi-frequency data including deep optical, UV, and narrow- band H{alpha} imaging and HI data to understand the formation process which gave birth to this peculiar system. For this purpose, we measured: i) multi-wavelength radial surface brightness profiles of NGVS 3543 and compared them to the predictions of spectro-photometric models of galaxy evolution in rich clusters, ii) aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass. The comparison of the observations with the evolutionary models indicate that the NGVS 3543 has undergone a ram-pressure stripping (RPS) that peaked ~100Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, whose mass is ~10^8^M_{sun}_, forming star complexes of typical age ~20Myr and stellar mass ~10^4^M_{sun}_. These results suggest that we are observing for the first time the ongoing transformation of a gas-rich UDG into a red and quiescent UDG under the effect of a ram-pressure stripping event. The same process could thus explain the lack of star forming UDGs in rich environments observed in several nearby clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/128
- Title:
- NGVS. XIV. Bona fide Virgo cluster members
- Short Name:
- J/ApJ/890/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Next Generation Virgo Cluster Survey (NGVS) was designed to provide a deep census of baryonic structures in the Virgo cluster. The survey covers the 104deg^2^ area from the core of Virgo out to one virial radius, in the u*griz bandpasses, to a point-source depth of g~25.9mag (10{sigma}) and a single pixel surface brightness limit of {mu}_g_~29mag/arcsec^2^ (2{sigma} above the sky). Here we present the final catalog of 404 Virgo galaxies located within a 3.71deg^2^ (0.3Mpc^2^) region centered on M87, Virgo's dominant galaxy. Of these, 154 were previously uncataloged and span the range 17.8mag<g<23.7mag (-13.4mag<M_g_{<}-7.4mag at the 16.5Mpc distance of Virgo). Extensive simulations show that the NGVS catalog is complete down to g=18.6mag (M_g_=-12.5mag, corresponding to a stellar mass M~1.6x10^7^M_{sun}_ for an old stellar population), and 50% complete at g=22.0mag (M_g_=-9.1mag, M~6.2x10^5^M_{sun}_). The NGVS 50% completeness limit is 3mag deeper than that of the Virgo Cluster Catalog (VCC), which has served as Virgo's reference standard for over a quarter century, and 2mag deeper than the VCC detection limit. We discuss the procedure adopted for the identification of objects and the criteria used to assess cluster membership. For each of the 404 galaxies in the NGVS Virgo Cluster core catalog, we present photometric and structural parameters based on a nonparametric curve-of-growth and isophotal analysis, as well as parametric (Sersic, double-Sersic, and/or core-Sersic) fits to the one-dimensional surface brightness profiles and two-dimensional light distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/18
- Title:
- NGVS. XXIII. Nuclear star clusters
- Short Name:
- J/ApJ/878/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using deep, high-resolution optical imaging from the Next Generation Virgo Cluster Survey, we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 10^5^<~M*/M_{sun}_<~10^12^. The nucleation fraction reaches a peak value f_n_~90% for M*~10^9^M_{sun}_ galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as M*~5x10^5^M_{sun}_. Comparison with literature data for nearby groups and clusters shows that at the low-mass end nucleation is more frequent in denser environments. The NSC mass function peaks at M_NSC_~7x10^5^M_{sun}_, a factor 3-4 times larger than the turnover mass for globular clusters (GCs). We find a nonlinear relation between the stellar masses of NSCs and those of their host galaxies, with a mean nucleus-to-galaxy mass ratio that drops to M_NSC_/M*~3.6x10^-3^ for M*~5x10^9^M_{sun}_ galaxies. Nuclei in both more and less massive galaxies are much more prominent: M_NSC_{propto}M_*_^0.46^ at the low-mass end, where nuclei are nearly 50% as massive as their hosts. We measure an intrinsic scatter in NSC masses at a fixed galaxy stellar mass of 0.4dex, which we interpret as evidence that the process of NSC growth is significantly stochastic. At low galaxy masses we find a close connection between NSCs and GC systems, including very similar occupation distributions and comparable total masses. We discuss these results in the context of current dissipative and dissipationless models of NSC formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/44
- Title:
- NGVS. XX. RedGOLD background galaxy clusters
- Short Name:
- J/ApJ/829/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We build a background cluster candidate catalog from the Next Generation Virgo Cluster Survey (NGVS) using our detection algorithm RedGOLD. The NGVS covers 104deg^2^ of the Virgo cluster in the u^*^,g,r,i,z-bandpasses to a depth of g~25.7mag (5{sigma}). Part of the survey was not covered or has shallow observations in the r band. We build two cluster catalogs: one using all bandpasses, for the fields with deep r-band observations (~20deg^2^), and the other using four bandpasses (u^*^,g,i,z) for the entire NGVS area. Based on our previous Canada-France-Hawaii Telescope Legacy Survey W1 studies, we estimate that both of our catalogs are ~100% (~70%) complete and ~80% pure, at z<=0.6 (z<~1), for galaxy clusters with masses of M>~10^14^M_{sun}_. We show that when using four bandpasses, though the photometric redshift accuracy is lower, RedGOLD detects massive galaxy clusters up to z~1 with completeness and purity similar to the five-band case. This is achieved when taking into account the bias in the richness estimation, which is ~40% lower at 0.5<=z<0.6 and ~20% higher at 0.6<z<0.8, with respect to the five-band case. RedGOLD recovers all the X-ray clusters in the area with mass M_500_>1.4x10^14^M_{sun}_ and 0.08<z<0.5. Because of our different cluster richness limits and the NGVS depth, our catalogs reach lower masses than the published redMaPPer cluster catalog over the area, and we recover ~90%-100% of its detections.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/12
- Title:
- NGVS XXV. Virgo globular clusters photometry
- Short Name:
- J/ApJS/227/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central region of the Virgo cluster of galaxies contains thousands of globular clusters (GCs), an order of magnitude more than the numbers found in the Local Group. Relics of early star formation epochs in the universe, these GCs also provide ideal targets to test our understanding of the Spectral Energy Distributions (SEDs) of old stellar populations. Based on photometric data from the Next Generation Virgo cluster Survey (NGVS) and its near-infrared counterpart NGVS-IR, we select a robust sample of ~2000 GCs with excellent photometry and spanning the full range of colors present in the Virgo core. The selection exploits the well defined locus of GCs in the uiK diagram and the fact that the globular clusters are marginally resolved in the images. We show that the GCs define a narrow sequence in 5-dimensional color space, with limited but real dispersion around the mean sequence. The comparison of these SEDs with the predictions of eleven widely used population synthesis models highlights differences between models, and also shows that no single model adequately matches the data in all colors. We discuss possible causes for some of these discrepancies. Forthcoming papers of this series will examine how best to estimate photometric metallicities in this context, and compare the Virgo globular cluster colors with those in other environments.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/17
- Title:
- NGVS. XXXIV. Ultracompact dwarf galaxies in Virgo
- Short Name:
- J/ApJS/250/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of ultracompact dwarf (UCD) galaxies in the Virgo cluster based mainly on imaging from the Next Generation Virgo Cluster Survey (NGVS). Using ~100deg^2^ of u*giz imaging, we have identified more than 600 candidate UCDs, from the core of Virgo out to its virial radius. Candidates have been selected through a combination of magnitudes, ellipticities, colors, surface brightnesses, half-light radii, and, when available, radial velocities. Candidates were also visually validated from deep NGVS images. Subsamples of varying completeness and purity have been defined to explore the properties of UCDs and compare to those of globular clusters and the nuclei of dwarf galaxies with the aim of delineating the nature and origins of UCDs. From a surface density map, we find the UCDs to be mostly concentrated within Virgo's main subclusters, around its brightest galaxies. We identify several subsamples of UCDs-i.e., the brightest, largest, and those with the most pronounced and/or asymmetric envelopes-that could hold clues to the origin of UCDs and possible evolutionary links with dwarf nuclei. We find some evidence for such a connection from the existence of diffuse envelopes around some UCDs and comparisons of radial distributions of UCDs and nucleated galaxies within the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A12
- Title:
- NIKA maps of ClG J1226.9+3332 at 150 and 250GHz
- Short Name:
- J/A+A/576/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The thermal Sunyaev-Zel'Dovich (tSZ) effect is expected to provide a low scatter mass proxy for galaxy clusters since it is directly proportional to the cluster thermal energy. The tSZ observations have proven to be a powerful tool for detecting and studying them, but high angular resolution observations are now needed to push their investigation to a higher redshift. In this paper, we report high angular (<20-arcsec) resolution tSZ observations of the high-redshift cluster CL J1226.9+3332 (z=0.89). It was imaged at 150 and 260GHz using the NIKA camera at the IRAM 30-meter telescope. The 150GHz map shows that CL J1226.9+3332 is morphologically relaxed on large scales with evidence of a disturbed core, while the 260GHz channel is used mostly to identify point source contamination. NIKA data are combined with those of Planck and X-ray from Chandra to infer the cluster's radial pressure, density, temperature, and entropy distributions. The total mass profile of the cluster is derived, and we find M_500_=5.96^+1.02^_-0.79_x10^14^M_{sun} within the radius R_500_=930^+50^_-43kpc, at a 68% confidence level. (R_500_ is the radius within which the average density is 500 times the critical density at the cluster's redshift.) NIKA is the prototype camera of NIKA2, a KIDs (kinetic inductance detectors) based instrument to be installed at the end of 2015. This work is, therefore, part of a pilot study aiming at optimizing tSZ NIKA2 large programs.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A118
- Title:
- NIKA Sunyaev-Zel'dovich data release
- Short Name:
- J/A+A/614/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Substructures in the hot gas atmosphere of galaxy clusters are related to their formation history and to the astrophysical processes at play in the intracluster medium (ICM). The thermal Sunyaev-Zel'dovich (tSZ) effect is directly sensitive to the line-of-sight integrated ICM pressure, and is thus particularly adapted to study ICM substructures. In this paper, we apply structure-enhancement filtering algorithms to high-resolution tSZ observations (e.g., NIKA) of distant clusters in order to search for pressure discontinuities, compressions, and secondary peaks in the ICM. The same filters are applied to toy-model images and to synthetic tSZ images extracted from RHAPSODY-G cosmological hydrodynamic simulations, in order to better interpret the extracted features. We also study the noise propagation through the filters and quantify the impact of systematic effects, such as data-processing-induced artifacts and point-source residuals, the latter being identified as the dominant potential contaminant. In three of our six NIKA-observed clusters we identify features at high signal-to-noise ratio that show clear evidence for merger events. In MACS J0717.5+3745 (z=0.55), three strong pressure gradients are observed on the east, southeast, and west sectors, and two main peaks in the pressure distribution are identified. We observe a lack of tSZ compact structure in the cool-core cluster PSZ1 G045.85+57.71 (z=0.61), and a tSZ gradient ridge dominates in the southeast. In the highest redshift cluster, CL J1226.9+3332 (z=0.89), we detect a ridge pressure gradient of ~45-arcsec (360kpc) in length associated with a secondary pressure peak in the west region. Our results show that current tSZ facilities have now reached the angular resolution and sensitivity to allow an exploration of the details of pressure substructures in clusters, even at high redshift. This opens the possibility to quantify the impact of the dynamical state on the relation between the tSZ signal and the mass of clusters, which is important when using tSZ clusters to test cosmological models. This work also marks the first NIKA cluster sample data release.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/22
- Title:
- NIR galaxy cluster candidates in the SPT survey
- Short Name:
- J/ApJ/761/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the ground- and space-based optical and near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with the Sunyaev-Zel'dovich (SZ) effect in the 720deg^2^ of the South Pole Telescope (SPT) survey completed in the 2008 and 2009 observing seasons. We use the optical/NIR data to establish whether each candidate is associated with an overdensity of galaxies and to estimate the cluster redshift. Most photometric redshifts are derived through a combination of three different cluster redshift estimators using red-sequence galaxies, resulting in an accuracy of {Delta}z/(1+z)=0.017, determined through comparison with a subsample of 57 clusters for which we have spectroscopic redshifts. We successfully measure redshifts for 158 systems and present redshift lower limits for the remaining candidates. The redshift distribution of the confirmed clusters extends to z=1.35 with a median of z_med_=0.57. Approximately 18% of the sample with measured redshifts lies at z>0.8. We estimate a lower limit to the purity of this SPT SZ-selected sample by assuming that all unconfirmed clusters are noise fluctuations in the SPT data. We show that the cumulative purity at detection significance {xi}>5 ({xi}>4.5) is >=95% (>=70%). We present the red brightest cluster galaxy (rBCG) positions for the sample and examine the offsets between the SPT candidate position and the rBCG. The radial distribution of offsets is similar to that seen in X-ray-selected cluster samples, providing no evidence that SZ-selected cluster samples include a different fraction of recent mergers from X-ray-selected cluster samples.
