Assessing the Evolution of Mine Water Quality With Empirical \u27First-Flush\u27 Models

Coal mining activities can leave an extensive network of abandoned underground workings that gradually flood after operations cease. This rising mine water, with low pH and high sulfate, acidity, and metals can lead to uncontrolled releases of harmful acid mine drainage to the environment. Treatment plants are used to extract and treat the mine water to maintain its elevations below suspected discharge zones. Accurate predictions of long-term water quality is highly challenging due to the complexity and volume of the underground workings. As numerical models have difficulty recreating complex mine pool geometry and hydrogeochemical processes, empirical models that are based on Younger’s ‘first-flush’ phenomenon, where mine water concentrations peak shortly after flooding and then exponentially decline, may provide better long-term predictive modeling. The objective of this study was to assess the robustness of ‘first-flush’ empirical models for describing and predicting mine water behavior at large, complex mine pools in The Sydney Coalfield (Nova Scotia, Canada). Numerous mine pools in the coalfield flooded at various times over 100+ years, allowing long-term mine water evolution to be studied in various pools of different ages. Analysis of extensive historical data from the older pools demonstrated that the evolving mine water quality, both overall and within each stratified layer, followed the ‘first-flush’ phenomenon. ‘First-flush’ trends were consistent across differing depths, water quality parameters (acidity, sulfate, iron), and concentration ranges. Two newer mine pools, which recently flooded in 2012, rely on a new active treatment plant to manage mine water levels below discharge points. Using behavioral conditions observed in the older mines, such as decay rate, ‘first-flush’ based empirical models were calibrated and validated to early mine water quality data collected at the treatment plant bi-weekly between 2012 and 2021. They were then used to predict future mine water quality and estimates of long-term treatment requirements and related expenses

The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies

We investigate the connection between globular clusters and ultracompact dwarf galaxies (UCDs) by examining the properties of 10 compact, high-luminosity (-11.8 MV -10.8) objects associated with M87 (NGC 4486, VCC 1316), the cD galaxy in the Virgo Cluster. These objects, most of which were previously classified as M87 globular clusters, were selected from a combination of ground- and space-based imaging surveys. Our observational database for these objects—which we term DGTOs, or dwarf-globular transition objects —includes Advanced Camera for Surveys (ACS) F475W and F850LP imaging from the ACS Virgo Cluster Survey, integrated-light spectroscopy from Keck/ESI, and archival F606W WFPC2 imaging. We also present a search for DGTOs associated with other galaxies based on ACS imaging for 100 early-type galaxies in Virgo

The ACS Fornax Cluster Survey. II. The Central Brightness Profiles of Early-Type Galaxies: A Characteristic Radius on Nuclear Scales and the Transition from Central Luminosity Deficit to Excess

We analyse brightness profiles for 143 early-type galaxies in the Virgo and Fornax Clusters, observed with the Advanced Camera for Surveys on the Hubble Space Telescope. S´ersic models are found to provide accurate representations of the global profiles with a notable exception: the observed profiles deviate systematically inside a characteristic “break” radius of Rb ≈ 0.02+0.025 −0.01 Re, where Re is the effective radius of the galaxy. The sense of the deviation is such that bright galaxies (MB . −20) typically show central light deficits with respect to the inward extrapolation of the S´ersic model, while the great majority of low- and intermediate-luminosity galaxies (−19.5 . MB . −15) show central light excesses; galaxies of intermediate luminosities (−20 . MB . −19.5) are generally well fitted by S´ersic models over all radii. We show that the slope, ′, of the central surface brightness profiles, when measured at fixed fractions of Re, varies smoothly as a function of galaxy luminosity in a manner that depends sensitively on the choice of measurement radius. We find no evidence for a core/power-law dichotomy, and show that a recent claim of strong bimodality in ′ is likely an artifact of the biased galaxy selection function used in that study. To provide a more robust characterization of the inner regions of galaxies, we introduce a parameter, 0.02 = log (Lg/Ls) — where Lg and Ls are the integrated luminosities inside 0.02Re of the observed profile and of the inward extrapolation of the outer S´ersic model — to describe the central luminosity deficit ( 0.02 \u3c 0) or excess ( 0.02 \u3e 0). We find that 0.02 varies smoothly over the range of ≈ 720 in luminosity spanned by the sample galaxies, with again no evidence for a dichotomy. We argue that the central light excesses in MB & −19 galaxies may be the analogs of the dense central cores predicted by some numerical simulations to form via gas inflows

Trends in the Globular Cluster Luminosity Function of Early-Type Galaxies

We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 earlytype galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parametrization of the GCLF, we find a highly significant correlation between the GCLF dispersion, , and the galaxy luminosity, MB,gal, in the sense that the GC systems in fainter galaxies have narrower luminosity functions. The GCLF dispersions in the Milky Way and M31 are fully consistent with this trend, implying that the correlation between sigma and galaxy luminosity is more fundamental than older suggestions that GCLF shape is a function of galaxy Hubble type. We show that the -MB,gal relation results from a bonafide narrowing of the distribution of (logarithmic) cluster masses in fainter galaxies. We further show that this behavior is mirrored by a steepening of the GC mass function for relatively high masses,M& 3×105M⊙, a mass regime in which the shape of the GCLF is not strongly affected by dynamical evolution over a Hubble time. We argue that this trend arises from variations in initial conditions and requires explanation by theories of cluster formation. Finally, we confirm that in bright galaxies, the GCLF “turns over at the canonicalmass scale ofMTO ≃2×105M⊙. However, we find thatMTO scatters to lower values (≈ 1-2×105M⊙) in galaxies fainter than MB,gal & -18.5, an important consideration if the GCLF is to be used as a distance indicator for dwarf ellipticals

The ACS Virgo Cluster Survey. X. Half-Light Radii of Globular Clusters in Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for Distance Estimation

We have measured half-light radii, rh, for thousands of globular clusters (GCs) belonging to the one hundred early-type galaxies observed in the ACS Virgo Cluster Survey and the elliptical galaxy NGC 4697. An analysis of the dependencies of the measured half-light radii on both the properties of the GCs themselves and their host galaxies reveals that, in analogy with GCs in the Galaxy but in a milder fashion, the average half-light radius increases with increasing galactocentric distance or, alternatively, with decreasing galaxy surface brightness. For the first time, we find that the average half-light radius decreases with the host galaxy color. We also show that there is no evidence for a variation of rh with the luminosity of the GCs. Finally, we find in agreement with previous observations that the average rh depends on the color of GCs, with red GCs being ∼ 17% smaller than their blue counterparts. We show that this difference is probably a consequence of an intrinsic mechanism, rather than projection effects, and that it is in good agreement with the mechanism proposed in Jord´an (2004). We discuss these findings in light of two simple pictures for the origin of the rh of GCs and show that both lead to a behavior in rough agreement with the observations. After accounting for the dependencies on galaxy color, galactocentric radius and underlying surface brightness, we show that the average GC half-light radii hrhi can be successfully used as a standard ruler for distance estimation. We outline the methodology, provide a calibration for its use, and discuss the prospects for this distance estimator with future observing facilities. We find hrhi = 2.7± 0.35 pc for GCs with (g − z) = 1.2 mag in a galaxy with color (g − z)gal = 1.5 mag and at an underlying surface z-band brightness of μz = 21 mag arcsec−2. Using this technique, we place an upper limit of 3.4 Mpc on the 1- line-of-sight depth of the Virgo Cluster. Finally, we examine the form of the rh distribution for our sample galaxies and provide an analytic expression which successfully describes this distribution

A Fundamental Relation between Compact Stellar Nuclei, Supermassive Black Holes, and Their Host Galaxies

Imaging surveys with the Hubble Space Telescope (HST) have shown that 50–80% of low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. We combine HST imaging for early-type galaxies from the ACS Virgo Cluster Survey with ground-based long-slit spectra from KPNO to show that the masses of compact stellar nuclei in Virgo Cluster galaxies obey a tight correlation with the masses of the host galaxies. The same correlation is obeyed by the supermassive black holes (SBHs) found in predominantly massive galaxies. The compact stellar nuclei in the Local Group galaxies M33 and NGC 205 are also found to fall along this same scaling relation. These results indicate that a generic by-product of galaxy formation is the creation of a central massive object (CMO) — either a SBH or a compact stellar nucleus — that contains a mean fraction, 0.2%, of the total galactic mass. In galaxies with masses greater than Mgal a few 1010M⊙, SBHs appear to be the dominant mode of CMO formation

The ACS Virgo Cluster Survey II. Data Reduction Procedures

The ACS Virgo Cluster Survey is a large program to carry out multi-color imaging of 100 early-type members of the Virgo Cluster using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Deep F475W and F850LP images (~ SDSS g and z) are being used to study the central regions of the program galaxies, their globular cluster systems, and the three-dimensional structure of Virgo itself. In this paper, we describe in detail the data reduction procedures used for the survey, including image registration, drizzling strategies, the computation of weight images, object detection, the identification of globular cluster candidates, and the measurement of their photometric and structural parameters.Comment: 33 pages, 8 figures. Accepted for publication in ApJS. Also available at http://www.physics.rutgers.edu/~pcote/acs/publications.htm

Trends in the Globular Cluster Luminosity Function of Early-Type Galaxies

We present results from a study of the globular cluster luminosity function (GCLF) in a sample of 89 early-type galaxies observed as part of the ACS Virgo Cluster Survey. Using a Gaussian parametrization of the GCLF, we find a highly significant correlation between the GCLF dispersion, sigma, and the galaxy luminosity, M_B, in the sense that the GC systems in fainter galaxies have narrower luminosity functions. The GCLF dispersions in the Milky Way and M31 are fully consistent with this trend, implying that the correlation between sigma and galaxy luminosity is more fundamental than older suggestions that GCLF shape is a function of galaxy Hubble type. We show that the sigma - M_B relation results from a bonafide narrowing of the distribution of (logarithmic) cluster masses in fainter galaxies. We further show that this behavior is mirrored by a steepening of the GC mass function for relatively high masses, M >~ 3 x 10^5 M_sun, a mass regime in which the shape of the GCLF is not strongly affected by dynamical evolution over a Hubble time. We argue that this trend arises from variations in initial conditions and requires explanation by theories of cluster formation. Finally, we confirm that in bright galaxies, the GCLF "turns over" at the canonical mass scale of M_TO ~ 2 x 10^5 M_sun. However, we find that M_TO scatters to lower values (~1-2 x 10^5 M_sun) in galaxies fainter than M_B >~ -18.5, an important consideration if the GCLF is to be used as a distance indicator for dwarf ellipticals.Comment: 4 pages, 3 figures. Accepted for publication in ApJ Letters. Also available at http://www.cadc.hia.nrc.gc.ca/community/ACSVCS/publications.htm

The ACS Virgo Cluster Survey IV: Data Reduction Procedures for Surface Brightness Fluctuation Measurements with the Advanced Camera for Surveys

The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of the Wide Field Channel of the ACS instrument on the Hubble Space Telescope (HST). The scientific goals of this survey include an exploration of the three-dimensional structure of the Virgo Cluster and a critical examination of the usefulness of the globular cluster luminosity function as a distance indicator. Both of these issues require accurate distances for the full sample of 100 program galaxies. In this paper, we describe our data reduction procedures and examine the feasibility of accurate distance measurements using the method of surface brightness fluctuations (SBF) applied to the ACS Virgo Cluster Survey F850LP imaging. The ACS exhibits significant geometrical distortions due to its off-axis location in the HST focal plane; correcting for these distortions by resampling the pixel values onto an undistorted frame results in pixel correlations that depend on the nature of the interpolation kernel used for the resampling. This poses a major challenge for the SBF technique, which normally assumes a flat power spectrum for the noise. We investigate a number of different interpolation kernels and show through an analysis of simulated galaxy images having realistic noise properties that it is possible, depending on the kernel, to measure SBF distances using distortion-corrected ACS images without introducing significant additional error from the resampling. We conclude by showing examples of real image power spectra from our survey.Comment: ApJS, in press, complete version of the paper at the link: http://www.physics.rutgers.edu/~pcote/acs/publications.htm