Proceedings of the International Astronomical Union
We describe an algorithm that can fit the properties of the dwarf galaxy progenitor of a tidal st... more We describe an algorithm that can fit the properties of the dwarf galaxy progenitor of a tidal stream, given the properties of that stream. We show that under ideal conditions (the Milky Way potential, the orbit of the dwarf galaxy progenitor, and the functional form of the dwarf galaxy progenitor are known exactly), the density and angular width of stars along the stream can be used to constrain the mass and radial profile of both the stellar and dark matter components of the progenitor dwarf galaxy that was ripped apart to create the stream. Our provisional fit for the parameters of the dwarf galaxy progenitor of the Orphan Stream indicates that it is less massive and has fewer stars than previous works have indicated.
We propose and test a method for applying statistical photometric parallax to main-sequence turno... more We propose and test a method for applying statistical photometric parallax to main-sequence turnoff stars in the Sloan Digital Sky Survey (SDSS). Using simulated data, we show that if our density model is similar to the actual density distribution of our data, we can reliably determine the density model parameters of three major substructures in the Milky Way halo using the computational resources available on MilkyWay@home (a 20-parameter fit). We fit the stellar density in SDSS stripe 19 with a smooth stellar spheroid component and three major streams. One of these streams is consistent with the Sagittarius tidal stream at 21.1 kpc away, one is consistent with the trailing tail of the Sagittarius tidal stream in the north Galactic cap at 48 kpc away, and one is possibly part of the Virgo Overdensity at 6 kpc away. We find the 1σ widths of these three streams to be 1.0 kpc, 17.6 kpc, and 6.1 kpc, respectively. The width of the trailing tail is extremely wide (41 kpc full width at half maximum). This large width could have implications for the shape of the Milky Way dark matter halo. The width of the Virgo Overdensity-like structure is consistent with what we might expect for a "cloudlike" structure; analysis of additional stripes of data are needed to outline the full extent of this structure and confirm its association with the Virgo Overdensity.
Symposium - International Astronomical Union, 2004
We present a new estimate of the mass of the Milky Way, making use of a large sample of 955 field... more We present a new estimate of the mass of the Milky Way, making use of a large sample of 955 field horizontal-branch (FHB) stars from the Early Data Release of the Sloan Digital Sky Survey. This sample of stars has been classified on the basis of an automated analysis approach, in combination with other methods, in order to obtain estimates of the physical parameters of the stars, i.e., Teff, log g, [Fe/H], and should be relatively free of contamination from halo blue stragglers. the stars all have measured radial velocities and photometric distance estimates, and the sample includes objects as distant as ~ 75 kpc from the Galactic center. Application of a Bayesian likelihood method, for a specific model of the Galaxy, indicates that the total mass of the Galaxy lies in the range 1.5 − 4.0 × 1012 M⊙. Our sample appears to reveal a clear signature of a dual halo population of FHB stars, with the boundary between the inner and outer halo around 20 kpc, and the possibility of rather str...
We describe the development and implementation of the SEGUE (Sloan Extension for Galactic Explora... more We describe the development and implementation of the SEGUE (Sloan Extension for Galactic Exploration and Understanding) Stellar Parameter Pipeline (SSPP). The SSPP derives, using multiple techniques, radial velocities and the fundamental stellar atmospheric parameters (effective temperature, surface gravity, and metallicity) for AFGK-type stars, based on medium-resolution spectroscopy and $ugriz$ photometry obtained during the course of the original Sloan Digital Sky Survey (SDSS-I) and its Galactic extension (SDSS-II/SEGUE). The SSPP also provides spectral classification for a much wider range of stars, including stars with temperatures outside of the window where atmospheric parameters can be estimated with the current approaches. This is Paper I in a series of papers on the SSPP; it provides an overview of the SSPP, and initial tests of its performance using multiple data sets. Random and systematic errors are critically examined for the current version of the SSPP, which has been used for the sixth public data release of the SDSS (DR-6).
The Kinematic Signature of the Sagittarius Dwarf Galaxy Tidal Debris from SDSS-DR1
Recent results from the Sloan Digital Sky Survey (SDSS) and the 2MASS All-Sky Survey have clearly... more Recent results from the Sloan Digital Sky Survey (SDSS) and the 2MASS All-Sky Survey have clearly revealed the extent of the spatial distribution of stars affiliated with the tidal debris tail of the Sagittarius Dwarf Galaxy (Sgr). Although these surveys help to constrain the shape of the Sgr orbit, kinematics of the tidal tail stars are crucial in order to
The LAMOST Spectroscopic Survey of Milky Way Stars (LEGUE)
Bulletin of the American Astronomical Society, 2009
ABSTRACT The Guo Shoujing Telescope (GSJT, formerly LAMOST) pilot survey started in October 2011 ... more ABSTRACT The Guo Shoujing Telescope (GSJT, formerly LAMOST) pilot survey started in October 2011 and will run through April 2012. We report on the footprint and selection algorithms for the stellar portion of the survey (LEGUE).
Seventeen of twenty known or suspected dwarf galaxy satellites of the Milky Way were discovered t... more Seventeen of twenty known or suspected dwarf galaxy satellites of the Milky Way were discovered through photometric images. Six significant tidal streams are known in the Galactic spheroid, all of which were discovered through photometric surveys. At present, only photometric surveys provide enough sky coverage and depth to probe the shape of the Milky Way. We argue that the Virgo Stellar Stream, which might be a stream or a disrupting dwarf galaxy, has a center 14-19 kpc from the Sun in the direction (l,b)=(300o,64o), using photometry from the Sloan Digital Sky Survey (SDSS) and the Sloan Extension for Galactic Understanding and Exploration (SEGUE). In the process, we demonstrate the importance of large, deep, multi-color, public photometric sky surveys with precision color information. Currently, the most urgent need is for data in the southern hemisphere and at low Galactic latitude. Deeper surveys would also be useful.
Tracing the Sagittarius Tidal Stream with Maximum Likelihood
AIP Conference Proceedings, 2008
Large scale surveys are providing vast amounts of data that can help us understand and study tida... more Large scale surveys are providing vast amounts of data that can help us understand and study tidal debris more easily and accurately. A maximum likelihood method for determining the spatial properties of this tidal debris and the stellar Galactic spheroid has been developed to take advantage of these huge datasets. We present the results of studying the Sagittarius dwarf tidal stream in two SDSS stripes taken in the southern Galactic Cap using this method. This study was done using stars with the colors of blue F turnoff stars in SDSS ...
Mapping the Sagittarius Dwarf Tidal Streams with Maximum Likelihood
Bulletin of the American Astronomical Society, 2009
Abstract We present spatial properties of the Sagittarius dwarf tidal stream at a number of point... more Abstract We present spatial properties of the Sagittarius dwarf tidal stream at a number of points across the sky. Using a proven maximum likelihood method for characterizing the properties of tidal debris, we calculate the spatial best-fit parameters of tidal debris, as well as the Galactic stellar spheroid, within a number of small (2.5 degree wide stripes) volumes. Using stars from SDSS DR6 having the colors of blue F turnoff stars with reddening corrected color values 0.1<(gr)< 0.3, we are able to determine the position, orientation, ...
Estimation of Elemental Abundances, Temperatures, and Surface Gravities for SDSS Stellar Spectra
Discovery of the true nature of the halo of the Galaxy has long been limited by the number of sta... more Discovery of the true nature of the halo of the Galaxy has long been limited by the number of stars with available spectroscopy and photometry. This constraint will soon be lifted. While undertaking a thorough spectroscopic follow-up of ~ 1,000,000 extragalactic sources, the Sloan Digital Sky Survey (SDSS) will ALSO obtain spectra of as many as ~ 100,000 Galactic sources
The Sloan Digital Sky Survey (SDSS) has scanned the entire region containing the Draco dwarf sphe... more The Sloan Digital Sky Survey (SDSS) has scanned the entire region containing the Draco dwarf spheroidal galaxy to 23rd magnitude in g*. We present a catalog of stars found in a 453 square arcminute, elliptical region centered on the Draco dwarf spheroidal galaxy. Objects in the catalog are matched with five previously published catalogs. The catalog contains SDSS photometry for 5634 individual objects, and also the photometry from matches to any of the other catalogs. A comparison of the photometry between catalogs allows us to identify 142 candidate variable objects. One hundred and twelve of the suspected variables have colors consistent with RR Lyrae variables.
ABSTRACT We explore disk kinematics using the Large Sky Area Area Mulit-Object Fiber Spectroscopi... more ABSTRACT We explore disk kinematics using the Large Sky Area Area Mulit-Object Fiber Spectroscopic Telescope (LAMOST) pilot survey. Spectra for 484,185 stars with magnitudes 10 to 18 were released after being observed using the Guo Shou Jing Telescope in the pilot survey. Because the majority of the stars with sufficient signal-to-noise for velocity measurements are bright, we focus our study on the Milky Way disk. We show the local kinematics of the disk using these stars, which show gradients in the radial and rotational motion along with longitudinal asymmetries. Funding for this project has been provided by The NASA/NY Space Grant, NSF grant AST 10-09670, NSF grant AST 09-37523 and NSFC grants 10973015 and 11061120454.
u*g*r*i*z* Photometry of stars, galaxies, QSOs (Newberg+ 1999)
The catalog (table 5 of the paper) contains the measurements of 2262 sources, including 334 exten... more The catalog (table 5 of the paper) contains the measurements of 2262 sources, including 334 extended sources, 1915 point sources, and 13 known QSOs, in five passbands close to the u&#39;g&#39;r&#39;i&#39;z&#39; passbands of SDSS (see the definition of the photometric system in Richards et al., 1997PASP..109...39R). Of these objects, over 1600 are measured in 15 fields covering 0.5deg2, with a limiting magnitude of r*&lt;19.5, similar to the photometric limit of the SDSS spectroscopic survey. (1 data file).
F-Turnoff Stars in Globular Clusters Palomar 13 and Whiting 1
ABSTRACT We use techniques of Newby et al. (2011) that established a mean magnitude of Mg=4.18 ± ... more ABSTRACT We use techniques of Newby et al. (2011) that established a mean magnitude of Mg=4.18 ± 0.008 for F-turnoff (FTO) stars in globular clusters within the Milky Way halo to analyze two globular clusters in the Southern Galactic Cap. Data from the two clusters, Palomar 13 and Whiting 1, recently became available in Data Release 8 (DR8) of the Sloan Digital Sky Survey (SDSS). Based on a histogram of the magnitude distribution, we find that the mean magnitude of FTO stars in Palomar 13 is Mg=4.46 ± 0.26 and the mean magnitude of FTO stars in Whiting 1 is Mg=4.11 ± 0.30. We confirm that the observed distribution of stars in these two clusters is consistent wiht the predictions of Newby et al.(2011), even though the two clusters are more distant than previously studied, and Whiting 1 is younger and more metal-rich than other globular clusters studied in this manner. We confirm previous results that indicate Whiting 1 is within the Sagittarius dwarf tidal stream, while Palomar 13 is not. This research was supported by NSF grant AST 10-09670.
Evidence that the Milky Way stellar spheroid is triaxial
We show star counts of spheroid stars over 5000 square degrees of sky from the SDSS DR3. The star... more We show star counts of spheroid stars over 5000 square degrees of sky from the SDSS DR3. The star counts are not symmetric about a Galactic longitude of zero degrees, at least out to 20 kpc from the Galactic center. The star counts are consistent with symmetry about a Galactic latitude of zero degrees. The best fit triaxial halo gives a major axis of the spheroid in the Galactic plane and roughly perpendicular to the Galactic bar. This research is funded by NSF, Research Corporation, and Fermilab DOE, using data from the Sloan Digital Sky Survey.
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Papers by Heidi Newberg