As the remnants of stars with initial masses 8 M , white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band ...photometry from the Canada-France Imaging Survey, griz photometry from Pan-STARRS1, as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over ∼4500 deg2 using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given star formation history, while simultaneously taking into account the geometry of the Milky Way (MW), survey parameters, and selection effects. We use this model to derive the star formation histories of the thin disk, thick disk, and stellar halo. Our results show that the MW disk began forming stars (11.3 0.5) Gyr ago, with a peak rate of (8.8 1.4) M yr −1 at (9.8 0.4) Gyr, before a slow decline to a constant rate until the present day-consistent with recent results suggesting a merging event with a satellite galaxy. Studying the residuals between the data and best-fit model shows evidence for a slight increase in star formation over the past 3 Gyr. We fit the local fraction of helium-atmosphere white dwarfs to be (21 3)%. Incorporating this methodology with data from future wide-field surveys such as the Large Synoptic Survey Telescope, Euclid, The Cosmological Advanced Survey Telescope for Optical and ultraviolet Research, and the Wide Field Infrared Survey Telescope should provide an unprecedented view into the formation of the MW at its earliest epoch through its white dwarfs.
We present a photometric study of the dwarf galaxy population in the core region ( rvir/4) of the Fornax galaxy cluster based on deep u′g′i′ photometry from the Next Generation Fornax Cluster Survey. ...All imaging data were obtained with the Dark Energy Camera mounted on the 4 m Blanco telescope at the Cerro Tololo Interamerican Observatory. We identify 258 dwarf galaxy candidates with luminosities −17 Mg′ −8 mag, corresponding to typical stellar masses of , reaching ∼3 mag deeper in point-source luminosity and ∼4 mag deeper in surface brightness sensitivity compared to the classic Fornax Cluster Catalog. Morphological analysis shows that the dwarf galaxy surface-brightness profiles are well represented by single-component Sérsic models with average Sérsic indices of and average effective radii of . Color-magnitude relations indicate a flattening of the galaxy red sequence at faint galaxy luminosities, similar to the one recently discovered in the Virgo cluster. A comparison with population synthesis models and the galaxy mass-metallicity relation reveals that the average faint dwarf galaxy is likely older than ∼5 Gyr. We study galaxy scaling relations between stellar mass, effective radius, and stellar mass surface density over a stellar mass range covering six orders of magnitude. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be identified: (1) dwarf galaxies assemble mass inside the half-mass radius up to , (2) isometric mass assembly occurs in the range , and (3) massive galaxies assemble stellar mass predominantly in their halos at and above.
Abstract
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 104 deg
2
area from the core of Virgo ...out to one virial radius, in the
u
*
griz
bandpasses, to a point-source depth of
g
∼ 25.9 mag (10
σ
) and a single pixel surface brightness limit of
μ
g
∼ 29 mag arcsec
−2
(2
σ
above the sky). Here we present the final catalog of 404 Virgo galaxies located within a 3.71 deg
2
(0.3 Mpc
2
) region centered on M87, Virgo’s dominant galaxy. Of these, 154 were previously uncataloged and span the range 17.8 mag <
g
< 23.7 mag (−13.4 mag <
M
g
< −7.4 mag at the 16.5 Mpc distance of Virgo). Extensive simulations show that the NGVS catalog is complete down to
g
= 18.6 mag (
M
g
= −12.5 mag, corresponding to a stellar mass
for an old stellar population), and 50% complete at
g
= 22.0 mag (
M
g
= −9.1 mag,
). The NGVS 50% completeness limit is 3 mag deeper than that of the Virgo Cluster Catalog (VCC), which has served as Virgo’s reference standard for over a quarter century, and 2 mag 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 (Sérsic, double-Sérsic, and/or core-Sérsic) fits to the one-dimensional surface brightness profiles and two-dimensional light distributions.
The Canada-France Imaging Survey (CFIS) will map the northern high Galactic latitude sky in the u-band ("CFIS-u," 10,000 ) and in the r-band ("CFIS-r," 5000 ), enabling a host of stand-alone science ...investigations, and providing some of the ground-based data necessary for photometric redshift determination for the Euclid mission. In this first contribution, we present the u-band component of the survey, describe the observational strategy, and discuss some first highlight results, based on approximately one-third of the final area. We show that the Galactic anticenter structure is distributed continuously along the line of sight, out to beyond , and possesses a metallicity distribution that is essentially identical to that of the outer disk sampled by APOGEE. This suggests that it is probably a buckled disk of old metal-rich stars, rather than a stream or a flare. We also discuss the future potential for CFIS-u in discovering star-forming dwarf galaxies around the Local Group, the characterization of the white dwarf and blue straggler population of the Milky Way, as well as its sensitivity to low surface brightness structures in external galaxies.
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 105 / 1012. The nucleation fraction reaches a peak value fn 90% for 109 galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as 5 × 105 . 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 MNSC 7 × 105 , 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 MNSC/M 3.6 × 10−3 for 5 × 109 galaxies. Nuclei in both more and less massive galaxies are much more prominent: 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 0.4 dex, 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.
We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg super(2)(0.3 Mpc super(2)) area in the core of the Virgo Cluster, based on u* griz data from the Next ...Generation Virgo Cluster Survey (NGVS). The galaxy sample which consists of 352 objects brighter than Mg= ?9.13 mag, the 50% completeness limit of the survey reaches 2.2 mag deeper than the widely used Virgo Cluster Catalog and at least 1.2 mag deeper than any sample previously used to measure the luminosity function in Virgo. Using a Bayesian analysis, we find a best-fit faint-end slope of alpha= ?1.33 + or - 0.02 for the g-band luminosity function; consistent results are found for the stellar mass function and the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultracompact dwarfs (UCDs) previously compiled by the NGVS in this region to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, Mg= ?9.6 mag) increases dramatically, up to alpha= ?1.60 + or - 0.06 when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo owing to the disruption of satellites, both nucleated and non-nucleated. We estimate that ~150 objects with Mg<,~ ?9.6 mag and that are currently classified as globular clusters might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the Virgo core might once have belonged to such satellites; these same disrupted satellites might have contributed ~40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group satellites, alpha= ?1.21 + or - 0.05, which is only 1.7sigma shallower than measured in the core of the Virgo Cluster.
Abstract We study the size and structure of globular cluster (GC) systems of 118 early-type galaxies from the NGVS, MATLAS, and ACSVCS surveys. Fitting Sérsic profiles, we investigate the ...relationship between effective radii of GC systems ( R e ,gc ) and galaxy properties. GC systems are 2–4 times more extended than host galaxies across the entire stellar mass range of our sample (10 8.3 M ⊙ < M * < 10 11.6 M ⊙ ). The relationship between R e ,gc and galaxy stellar mass exhibits a characteristic “knee” at a stellar mass of M p ≃ 10 10.8 , similar to the galaxy R e –stellar mass relationship. We present a new characterization of the traditional blue and red GC color subpopulations, describing them with respect to host galaxy ( g ′ − i ′ ) color (Δ gi ): GCs with similar colors to their hosts have a “red” Δ gi , and those significantly bluer GCs have a “blue” Δ gi . The GC populations with red Δ gi , even in dwarf galaxies, are twice as extended as the stars, suggesting that formation or survival mechanisms favor the outer regions. We find a tight correlation between R e ,gc and the total number of GCs, with intrinsic scatter ≲0.1 dex spanning two and three orders of magnitude in size and number, respectively. This holds for both red and blue subpopulations, albeit with different slopes. Assuming that N GC,Total correlates with M 200 , we find that the red GC systems have effective radii of roughly 1%–5% R 200 , while the blue GC systems in massive galaxies can have sizes as large as ∼10% R 200 . Environmental dependence on R e ,gc is also found, with lower-density environments exhibiting more extended GC systems at fixed mass.
The Next Generation Virgo Cluster Survey (NGVS) is a program that uses the 1 deg super(2) MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical imaging survey ...of the Virgo cluster, from its core to its virial radius-covering a total area of 104 deg super(2)-in the u*griz bandpasses. Thanks to a dedicated data acquisition strategy and processing pipeline, the NGVS reaches a point-source depth of g approx = 25.9 mag (10sigma) and a surface brightness limit of mu sub(g) ~ 29 mag arcsec super(-2) (2sigma above the mean sky level), thus superseding all previous optical studies of this benchmark galaxy cluster. In this paper, we give an overview of the technical aspects of the survey, such as areal coverage, field placement, choice of filters, limiting magnitudes, observing strategies, data processing and calibration pipelines, survey timeline, and data products. We also describe the primary scientific topics of the NGVS, which include: the galaxy luminosity and mass functions; the color-magnitude relation; galaxy scaling relations; compact stellar systems; galactic nuclei; the extragalactic distance scale; the large-scale environment of the cluster and its relationship to the Local Supercluster; diffuse light and the intracluster medium; galaxy interactions and evolutionary processes; and extragalactic star clusters. In addition, we describe a number of ancillary programs dealing with "foreground" and "background" science topics, including the study of high-inclination trans-Neptunian objects; the structure of the Galactic halo in the direction of the Virgo Overdensity and Sagittarius Stream; the measurement of cosmic shear, galaxy-galaxy, and cluster lensing; and the identification of distant galaxy clusters, and strong-lensing events.
Intracluster (IC) populations are expected to be a natural result of the hierarchical assembly of clusters, yet their low space densities make them difficult to detect and study. We present the first ...definitive kinematic detection of an IC population of globular clusters (GCs) in the Virgo cluster, around the central galaxy M87. This study focuses on the Virgo core, for which the combination of Next Generation Virgo Cluster Survey photometry and follow-up spectroscopy allows us to reject foreground star contamination and explore GC kinematics over the full Virgo dynamical range. The GC kinematics changes gradually with galactocentric distance, decreasing in mean velocity and increasing in velocity dispersion, eventually becoming indistinguishable from the kinematics of Virgo dwarf galaxies at R > 320 kpc. By kinematically tagging M87 halo and intracluster GCs, we find that (1) the M87 halo has a smaller fraction (52 3%) of blue clusters with respect to the IC counterpart (77 10%), (2) the (g′−r′)0 versus (i′−z′)0 color-color diagrams reveal a galaxy population that is redder than the IC population, which may be due to a different composition in chemical abundance and progenitor mass, and (3) the ICGC distribution is shallower and more extended than the M87 GCs, yet still centrally concentrated. The ICGC specific frequency, SN,ICL = 10.2 4.8, is consistent with what is observed for the population of quenched, low-mass galaxies within 1 Mpc from the cluster's center. The IC population at Virgo's center is thus consistent with being an accreted component from low-mass galaxies tidally stripped or disrupted through interactions, with a total mass of .
The NGVS-IR project (Next Generation Virgo Cluster Survey-Infrared) is a contiguous, near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of ...Virgo (NGVS). In its current state, NGVS-IR consists of Ks-band imaging of 4 deg2 centered on M87 and J- and Ks-band imaging of ~16 deg2 covering the region between M49 and M87.We present observations of the central 4 deg2 centered on Virgo's core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope, and the total integration time was 41 hr distributed over 34 contiguous tiles. Combining the Ks data with optical and ultraviolet data, we build the uiKsubs color-color diagram, which allows a very clean color-based selection of globular clusters in Virgo. Equipped with a powerful new tool, future NGVS-IR investigations based on the uiKsubs diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies.
PDF
