Paul Harding

Case Western Reserve University

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Heather Morrison

Holmes Regional Medical Center

Timothy C. Beers

Joint Institute for Nuclear Astrophysics

J. Christopher Mihos

Case Western Reserve University

Dmitry Bizyaev

Lomonosov Moscow State University

Jennifer A. Johnson

The Ohio State University

Ricardo P. Schiavon

Liverpool John Moores University

Kaike Pan

Chongqing University

Constance M. Rockosi

University of California, Santa Cruz

David J. Schlegel

Lawrence Berkeley National Laboratory

Carlos Allende Prieto

Instituto de Astrofísica de Canarias

Cooperative Institutions

Max Planck Society

167

Max Planck Institute for Astronomy

147

Center for Astrophysics Harvard & Smithsonian

132

Centre National de la Recherche Scientifique

116

University of Washington

100

Johns Hopkins University

Princeton University

Kitt Peak National Observatory

University of Virginia

The Ohio State University

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CHEMICAL CARTOGRAPHY WITH APOGEE: METALLICITY DISTRIBUTION FUNCTIONS AND THE CHEMICAL STRUCTURE OF THE MILKY WAY DISK

The Astrophysical Journal (2015)

Michael R. Hayden Jo Bovy Jon A. Holtzman David L. Nidever Jonathan C. Bird

Using a sample of 69,919 red giants from the SDSS-III/APOGEE Data Release 12, we measure the distribution of stars in the [α/Fe] versus [Fe/H] plane and the metallicity distribution functions (MDFs) across an unprecedented volume of the Milky Way disk, with radius 3 < R < 15 kpc and height kpc. Stars in the inner disk (R < 5 kpc) lie along a single track in [α/Fe] versus [Fe/H], starting with α-enhanced, metal-poor stars and ending at [α/Fe] ∼ 0 and [Fe/H] ∼ +0.4. At larger radii we find two distinct sequences in [α/Fe] versus [Fe/H] space, with a roughly solar-α sequence that spans a decade in metallicity and a high-α sequence that merges with the low-α sequence at super-solar [Fe/H]. The location of the high-α sequence is nearly constant across the disk; however, there are very few high-α stars at R > 11 kpc. The peak of the midplane MDF shifts to lower metallicity at larger R, reflecting the Galactic metallicity gradient. Most strikingly, the shape of the midplane MDF changes systematically with radius, from a negatively skewed distribution at 3 < R < 7 kpc, to a roughly Gaussian distribution at the solar annulus, to a positively skewed shape in the outer Galaxy. For stars with kpc or [α/Fe] > 0.18, the MDF shows little dependence on R. The positive skewness of the outer-disk MDF may be a signature of radial migration; we show that blurring of stellar populations by orbital eccentricities is not enough to explain the reversal of MDF shape, but a simple model of radial migration can do so.

Thick disk

Star count

10.1088/0004-637x/808/2/132

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Citations (544)

Mapping the Galactic Halo IV. Searching for Distant Giants with the Washington System

arXiv (Cornell University) (2000)

Helen Morrison Edward W. Olszewski Mario Mateo John E. Norris Paul Harding

Galactic corona

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Planetary Nebula Kinematics in M31

The Astrophysical Journal (2004)

Denise Hurley‐Keller Heather Morrison Paul Harding George H. Jacoby

We present kinematics of 135 planetary nebulae (PNs) in M31 from a survey covering 3.9 deg2 and extending out to 15 kpc from the southwest major axis and more than 20 kpc along the minor axis. The majority of our sample, even well outside the disk, shows significant rotational support (mean line-of-sight velocity 116 km s-1). We argue that these PNs belong to the outer part of M31's large R1/4 bulge. Only five PNs have velocities clearly inconsistent with this fast rotating bulge. All five may belong to tidal streams in M31's outer halo. One is projected on the Northern Spur and is counterrotating with respect to the disk there. Two are projected near the major axis at X = -10 kpc and have M32-like velocities; they could be debris from that galaxy. The remaining two halo PNs are located near the center of the galaxy, and their velocities follow the gradient found by Ibata and coworkers, implying that these PNs could belong to the Southern Stream. If M31 has a nonrotating, pressure-supported halo, we have yet to find it, and it must be a very minor component of the galaxy.

Andromeda Galaxy

10.1086/425110

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Citations (27)

SDSS-IV MaNGA IFS GALAXY SURVEY—SURVEY DESIGN, EXECUTION, AND INITIAL DATA QUALITY

The Astronomical Journal (2016)

Renbin Yan Kevin Bundy David R. Law Matthew A. Bershady Brett H. Andrews

The MaNGA Survey (Mapping Nearby Galaxies at Apache Point Observatory) is one of three core programs in the Sloan Digital Sky Survey IV. It is obtaining integral field spectroscopy (IFS) for 10K nearby galaxies at a spectral resolution of R~2000 from 3,622-10,354A. The design of the survey is driven by a set of science requirements on the precision of estimates of the following properties: star formation rate surface density, gas metallicity, stellar population age, metallicity, and abundance ratio, and their gradients; stellar and gas kinematics; and enclosed gravitational mass as a function of radius. We describe how these science requirements set the depth of the observations and dictate sample selection. The majority of targeted galaxies are selected to ensure uniform spatial coverage in units of effective radius (Re) while maximizing spatial resolution. About 2/3 of the sample is covered out to 1.5Re (Primary sample), and 1/3 of the sample is covered to 2.5Re (Secondary sample). We describe the survey execution with details that would be useful in the design of similar future surveys. We also present statistics on the achieved data quality, specifically, the point spread function, sampling uniformity, spectral resolution, sky subtraction, and flux calibration. For our Primary sample, the median r-band signal-to-noise ratio is ~73 per 1.4A pixel for spectra stacked between 1-1.5 Re. Measurements of various galaxy properties from the first year data show that we are meeting or exceeding the defined requirements for the majority of our science goals.

Stellar population

Sample (material)

10.3847/0004-6256/152/6/197

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Citations (165)

Results from a diffuse intracluster light survey

arXiv (Cornell University) (2003)

John J. Feldmeier J. Christopher Mihos Heather Morrison Paul Harding Cameron K. McBride

We give an update of our ongoing survey for intracluster light (ICL), in a sample of distant Abell clusters. We find that the amount of intracluster starlight is comparable to that seen in nearby clusters, and that tidal debris appears to be common.

Starlight

Intracluster medium

10.48550/arxiv.astro-ph/0310561

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HST/ACS Observations of M33's Outer Halo

Ata Sarajedini D. Geisler Paul Harding R. A. Schommer

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Exploring the Variable Sky with the Sloan Digital Sky Survey

The Astronomical Journal (2007)

Branimir Sesar Željko Ivezić Robert H. Lupton Mario Jurić James E. Gunn

We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations.The catalog covers SDSS stripe 82, which lies along the celestial equator in the southern Galactic hemisphere (22 h 24 m < J2000:0 < 04 h 08 m , À1:27 < J2000:0 < þ1:27 , $290 deg 2 ), and contains 34 million photometric observations in the SDSS ugriz system for 748,084 unresolved sources at high Galactic latitudes (b < À20 ) that were observed at least four times in each of the ugri bands (with a median of 10 observations obtained over $6 yr).In each photometric bandpass we compute various low-order light-curve statistics, such as rms scatter, 2 per degree of freedom, skewness, and minimum and maximum magnitude, and use them to select and study variable sources.We find that 2% of unresolved optical sources brighter than g ¼ 20:5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands (at high Galactic latitudes).The majority (2 out of 3) of these variable sources are low-redshift (<2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample.We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding lowredshift quasars as the UVexcess color selection (at high Galactic latitudes).We analyze the distribution of light-curve skewness for quasars and find that it is centered on zero.We find that about one-fourth of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level.The distribution of light-curve skewness in the g À r versus u À g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior).Using over 600 RR Lyrae stars, we demonstrate rich halo substructure out to distances of 100 kpc.We extrapolate these results to the expected performance by the Large Synoptic Survey Telescope and estimate that it will obtain well-sampled, 2% accurate, multicolor light curves for $2 million lowredshift quasars and discover at least 50 million variable stars.

10.1086/521819

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Citations (296)

The calcium abundances in NGC 6584, NGC 6864, and NGC 6981

Publications of the Astronomical Society of the Pacific (1990)

A. W. Rodgers Paul Harding

Intermediate-resolution spectra of horizontal-branch stars in the clusters NGC 6584, NGC 6864, and NGC 6981 are analyzed to derive calcium abundances. Measurements of the Ca II K line and higher Balmer line strengths indicate that the three clusters have near-identical calcium abundance with Ca/H = -1.01, -1.07, and -1.09 for NGC 6584, NGC 6864, and NGC 6981, respectively. The interstellar reddening, E(B - V), is found to be 0.11 for both NGC 6864 and NGC 6981. The less-precise determination for NGC 6864 agrees well with previous photometric determinations, but the value for NGC 6981 is higher than the value E(B - V) = 0.03 compiled by Webbink (1985). The resulting values of Fe/H = -1.5 are in good agreement with previous determinations.

Balmer series

Hubble sequence

Line (geometry)

10.1086/132632

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Citations (3)

The calcium abundance in NGC 1851

Publications of the Astronomical Society of the Pacific (1987)

A. W. Rodgers Paul Harding

Spectra have been obtained of eight horizontal branch stars including three RR Lyrae stars, in the globular cluster NGC 1851. The spectra were measured to obtain equivalent widths of Ca II K and profiles of the Hδ line. The equivalent width of the interstellar component of the K line is found to be 0.56 Å. Stetson's (1981) photometry of the cluster is used for an independent measurement of the interstellar reddening and his value of E(B-V) = 0.02±0.01 is confirmed. Measurement of the calcium and hydrogen lines leads to a value of [Ca/H] = -1.0±0.15.

RR Lyrae variable

Instability strip

Equivalent width

10.1086/132062

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Citations (2)

The Extragalactic Distance Scale Key Project. XVI. Cepheid Variables in an Inner Field of M101

The Astrophysical Journal (1998)

P. B. Stetson Abhijit Saha Laura Ferrarese Daya M. Rawson H. C. Ford

We report on the identification of 255 candidate variable stars in a field located some 17 from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Photometric measurements in the F555W and F814W filters—analyzed independently with the DAOPHOT/ALLFRAME and DoPHOT software suites—have been transformed to the Johnson V and Kron-Cousins I standard magnitude systems. Periods and intensity-averaged mean magnitudes for 61 carefully selected candidate Cepheid variables with periods in the range 10-48 days indicate a reddening-corrected mean distance modulus (m - M)0 = 29.05 ± 0.14 (if the true modulus of the Large Magellanic Cloud is 18.50 ± 0.10, and if there is no dependence of the period-luminosity relation on metal abundance); results consistent with this are obtained whether or not the sample is expanded to include a larger fraction of the candidates. Applying a metallicity-dependent correction of +0.16 ± 0.10 mag would increase this estimate to (m - M)0 = 29.21 ± 0.17 mag.

Distance modulus

Large Magellanic Cloud

Variable star

Cosmic distance ladder

10.1086/306443

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Citations (108)