Variable Sodium Absorption in a Low-extinction Type Ia Supernova (2009)
Simon, Joshua D., Gal-Yam, Avishay, Gnat, Orly, Quimby, Robert M., Ganeshalingam, Mohan, Silverman, Jeffrey M., ...
Recent observations have revealed that some Type Ia supernovae exhibit narrow, time-variable Na I D absorption features. The origin of the absorbing material is controversial, but it may suggest the...
Accurate masses for dispersion-supported galaxies (2009)
Wolf, Joe, Martinez, Gregory D., Bullock, James S., Kaplinghat, Manoj, Geha, Marla, Munoz, Ricardo R., ...
We derive an accurate mass estimator for dispersion-supported stellar systems and demonstrate its validity by analyzing resolved line-of-sight velocity data for globular clusters, dwarf galaxies, and...
Spectroscopic Confirmation of the Pisces Overdensity (2009)
Kollmeier, Juna A., Gould, Andrew, Shectman, Stephen, Thompson, Ian B., Preston, George W., Simon, Joshua D., ...
We present spectroscopic confirmation of the "Pisces Overdensity", also known as "Structure J", a photometric overdensity of RR Lyrae stars discovered by the Sloan Digital Sky Survey (SDSS) at an...
Variable Sodium Absorption in a Low-Extinction Type Ia Supernova (2009)
Simon, Joshua D., Gal-Yam, Avishay, Gnat, Orly, Quimby, Robert M., Ganeshalingam, Mohan, Silverman, Jeffrey M., ...
Recent observations have revealed that some Type Ia supernovae exhibit narrow, time-variable Na I D absorption features. The origin of the absorbing material is controversial, but it may suggest the...
The Least-Luminous Galaxy: Spectroscopy of the Milky Way Satellite Segue 1 (2009)
Geha, Marla, Willman, Beth, Simon, Joshua D., Strigari, Louis E., Kirby, Evan N., Law, David R., ...
We present Keck/DEIMOS spectroscopy of Segue 1, an ultra-low-luminosity (M_V = –1.5^(+0.6)_(–0.8)) Milky Way satellite companion. While the combined size and luminosity of Segue 1 are consistent...
Bullock, James S., Kaplinghat, Manoj, Fruchter, Andrew, Geha, Marla, Simon, Joshua D., Strigari, Louis E., ...
Over the past five years, searches in Sloan Digital Sky Survey data have more than doubled the number of known dwarf satellite galaxies of the Milky Way, and have revealed a population of ultra-faint...
Frebel, Anna, Simon, Joshua D., Geha, Marla, Willman, Beth
We present Keck/HIRES observations of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices. These observations include the first...
The Role of Dwarf Galaxies in Building Large Stellar Halos (2009)
Kirby, Evan N., Guhathakurta, Puragra, Bullock, James S., Frebel, Anna, Geha, Marla, Gilbert, Karoline M., ...
The hierarchical theory of galaxy formation rests on the idea that smaller galactic structures merge to form the galaxies that we see today. The past decade has provided remarkable observational...
The Chemical Abundances of Tycho G in Supernova Remnant 1572 (2009)
González Hernández, Jonay I., Ruiz-Lapuente, Pilar, Filippenko, Alexei V., Foley, Ryan J., Gal-Yam, Avishay, Simon, Joshua D.
We present an analysis of the chemical abundances of the star Tycho G in the direction of the remnant of supernova (SN) 1572, based on Keck high-resolution optical spectra. The stellar parameters of...
The chemical abundances of tycho G in supernova remnant 1572 (2009)
González Hernández, Jonay I., Ruiz-Lapuente, Pilar, Filippenko, Alexei V., Foley, Ryan J., Gal-Yam, Avishay, Simon, Joshua D.
Variable sodium absorption in a low-extinction type Ia supernova (2009)
Simon, Joshua D., Gal-Yam, Avishay, Gnat, Orly, Quimby, Robert M., Ganeshalingam, Mohan, Silverman, Jeffrey M., ...
Kirby, Evan N., Simon, Joshua D., Geha, Marla, Guhathakurta, Puragra, Frebel, Anna
We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way (MW) system. Our technique is based...
The Chemical Abundances of Tycho G in Supernova Remnant 1572 (2008)
Hernández, Jonay I. González, Ruiz-Lapuente, Pilar, Filippenko, Alexei V., Foley, Ryan J., Gal-Yam, Avishay, Simon, Joshua D.
We present an analysis of the chemical abundances of the star Tycho G in the direction of the remnant of supernova (SN) 1572, based on Keck high-resolution optical spectra. The stellar parameters of...
A common mass scale for satellite galaxies of the Milky Way (2008)
Strigari, Louis E., Bullock, James S., Kaplinghat, Manoj, Simon, Joshua D., Geha, Marla, Willman, Beth, ...
The Milky Way has at least twenty-three known satellite galaxies that shine with luminosities ranging from about a thousand to a billion times that of the Sun. Half of these galaxies were discovered...
Kirby, Evan N., Simon, Joshua D., Geha, Marla, Guhathakurta, Puragra, Frebel, Anna
We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way (MW) system. Our technique is based...
Strigari, Louis E., Koushiappas, Savvas M., Bullock, James S., Kaplinghat, Manoj, Simon, Joshua D., Geha, Marla, ...
We use kinematic data from three new nearby, extremely low luminosity Milky Way dwarf galaxies (Ursa Major II, Willman 1, and Coma Berenices) to constrain the properties of their dark matter halos,...
The M33 metallicity project: Resolving the abundance gradient discrepancies in M33 (2008)
Rosolowsky, Erik, Simon, Joshua D.
We present a new determination of the metallicity gradient in M33, based on Keck LRIS measurements of oxygen abundances using the temperature-sensitive emission line [O III] λ4363 in 61 H II...
A Metallicity Map of M33 (2007)
Simon, Joshua D., Rosolowsky, Erik
We present initial results from the M33 Metallicity Project. Out of the thousands of cataloged HII regions in M33, only ~30 have electron-temperature based abundances in the literature. We have...
The M33 Metallicity Project: Resolving the Abundance Gradient Discrepancies in M33 (2007)
Rosolowsky, Erik, Simon, Joshua D.
We present a new determination of the metallicity gradient in M33, based on Keck/LRIS measurements of oxygen abundances using the temperature-sensitive emission line [OIII] 4363 A in 61 HII regions....
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Strigari, Louis E., Koushiappas, Savvas M., Bullock, James S., Kaplinghat, Manoj, Simon, Joshua D., Geha, Marla, ...
We use kinematic data from three new, nearby, extremely low-luminosity Milky Way dwarf galaxies (Ursa Major II, Willman 1, and Coma Berenices) to constrain the properties of their dark matter halos,...
Constraints on Circumstellar Material Around the Type Ia Supernova 2007af (2007)
Simon, Joshua D., Gal-Yam, Avishay, Penprase, Bryan E., Li, Weidong, Quimby, Robert M., Silverman, Jeffrey M., ...
Patat et al. recently inferred the existence of circumstellar material around a normal Type Ia supernova (SN) for the first time, finding time-variable Na I D absorption lines in the spectrum of SN...
Simon, Joshua D., Bolatto, Alberto D., Whitney, Barbara A., Robitaille, Thomas P., Shah, Ronak Y., Makovoz, David, ...
We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S3MC) to study the young stellar content of N66, the largest and brightest HII region in the SMC. In...
The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem (2007)
We present Keck/DEIMOS spectroscopy of stars in 8 of the newly discovered ultra-faint dwarf galaxies around the Milky Way. We measure the velocity dispersions of Canes Venatici I and II, Ursa Major I...
A High-Resolution Spectrum of the Extremely Metal-rich Bulge G Dwarf OGLE-2006-BLG-265 (2007)
Johnson, Jennifer A., Gal-Yam, Avishay, Leonard, Douglas C., Simon, Joshua D., Udalski, Andrzej, Gould, Andrew
We present an R = 45,000 Keck spectrum of the microlensed Galactic bulge G dwarf OGLE-2006-BLG-265, which has high (~60) signal-to-noise ratio despite its short (15 minute) exposure time, because the...
Bolatto, Alberto D., Simon, Joshua D., Stanimirović, Snežana, Van Loon, Jacco Th., Shah, Ronak Y., Venn, Kim, ...
We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S^3MC), which imaged the star-forming body of the SMC in all seven MIPS and IRAC wave bands. We find that the...
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Self-consistent massive disks in triaxial dark matter halos (2007)
Bailin, Jeremy, Simon, Joshua D., Bolatto, Alberto D., Gibson, Brad K., Power, Chris
Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to...
Is there a fundamental line for disk galaxies? (2006)
Simon, Joshua D., Prada, Francisco, Vílchez, José M., Blitz, Leo, Robertson, Brant
We show that there are strong local correlations between metallicity, surface brightness, and dynamical mass-to-light ratio with M33, analogous to the fundamental line of dwarf galaxies identified by...
A High-Resolution Spectrum of the Extremely Metal-Rich Bulge G-Dwarf OGLE-2006-BLG-265 (2006)
Johnson, Jennifer A., Gal-Yam, Avishay, Leonard, Douglas C., Simon, Joshua D., Udalski, Andrzej, Gould, Andrew
We present an R=45,000 Keck spectrum of the microlensed Galactic bulge G-dwarf OGLE-2006-BLG-265, which has a high (~60) signal-to-noise ratio despite its short (15 min) exposure time because the...
Bolatto, Alberto D., Simon, Joshua D., Stanimirovic, Snezana, Van Loon, Jacco Th., Shah, Ronak Y., Venn, Kim, ...
We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S3MC), which imaged the star-forming body of the Small Magellanic Cloud (SMC) in all seven MIPS and IRAC...
Is There a Fundamental Line for Disk Galaxies? (2006)
Simon, Joshua D., Prada, Francisco, Vilchez, Jose M., Blitz, Leo, Robertson, Brant
We show that there are strong local correlations between metallicity, surface brightness, and dynamical mass-to-light ratio within M33, analogous to the fundamental line of dwarf galaxies identified...
Infrared Sources in the Small Magellanic Cloud: First Results (2006)
Simon, Joshua D., Bolatto, Alberto D., Stanimirovic, Snezana, Shah, Ronak Y., Leroy, Adam, Sandstrom, Karin
We have imaged the entire Small Magellanic Cloud (SMC), one of the two nearest star-forming dwarf galaxies, in all seven IRAC and MIPS bands. The low mass and low metallicity (1/6 solar) of the SMC...
The Cosmological Significance of High-Velocity Cloud Complex H (2005)
Simon, Joshua D., Blitz, Leo, Cole, Andrew A., Weinberg, Martin D., Cohen, Martin
We have used infrared and radio observations to search for a dwarf galaxy associated with the high-velocity cloud (HVC) known as Complex H. Complex H is a large (> 400 deg^2) and probably nearby (d =...
Spitzer Space Telescope detection of the young supernova remnant 1E 0102.2-7219 (2005)
Stanimirovic, Snezana, Bolatto, Alberto D., Sandstrom, Karin, Leroy, Adam K., Simon, Joshua D., Gaensler, B. M., ...
We present infrared observations of the young, oxygen-rich supernova remnant 1E 0102.2-7219 (E0102) in the Small Magellanic Cloud, obtained with the Spitzer Space Telescope. The remnant is detected...
Leroy, Adam, Bolatto, Alberto D., Simon, Joshua D., Blitz, Leo
We present a new survey for CO in dwarf galaxies using the Kitt Peak 12m telescope. We observed the central regions of 121 northern dwarfs with IRAS detections and no known CO emission. We detect CO...
Simon, Joshua D., Bolatto, Alberto D., Leroy, Adam, Blitz, Leo, Gates, Elinor L.
We derive rotation curves for four nearby, low-mass spiral galaxies and use them to constrain the shapes of their dark matter density profiles. This analysis is based on high-resolution...
Dark Matter in Dwarf Galaxies: High Resolution Observations (2003)
Bolatto, Alberto D., Simon, Joshua D., Leroy, Adam, Blitz, Leo
We present observations and analysis of rotation curves and dark matter halo density profiles in the central regions of four nearby dwarf galaxies. This observing program has been designed to...
Dark Matter in Dwarf Galaxies: The First Dark Galaxy? (2003)
Simon, Joshua D., Robishaw, Timothy, Blitz, Leo
We present new HI observations of the high-velocity cloud (HVC) that we resolved near the Local Group dwarf galaxy LGS 3. The cloud is rotating, with an implied mass that makes it dark...
Simon, Joshua D., Bolatto, Alberto D., Leroy, Adam, Blitz, Leo
We have obtained two-dimensional velocity fields of the dwarf spiral galaxy NGC 2976 in Halpha and CO. The high spatial (~75 pc) and spectral (13 km/s and 2 km/s, respectively) resolution of these...
HI Imaging of LGS 3 and an Apparently Interacting High-Velocity Cloud (2002)
Robishaw, Timothy, Simon, Joshua D., Blitz, Leo
We present a 93' by 93' map of the area near the Local Group dwarf galaxy LGS 3, centered on an HI cloud 30' away from the galaxy. Previous authors associated this cloud with LGS 3 but relied on...
The Absence of Stars in Compact High-Velocity Clouds (2002)
We present the results of our search for faint Local Group dwarf galaxies in compact high-velocity clouds (HVCs). We used digitized Palomar Observatory Sky Survey (POSS) data to examine 1 square...
The Density Profile of the Dark Matter Halo of NGC 4605 (2001)
Bolatto, Alberto D., Simon, Joshua D., Leroy, Adam, Blitz, Leo
We have obtained ~100 pc resolution CO and ~60 pc resolution Halpha observations of the dwarf spiral galaxy NGC 4605. We use them to derive a high resolution rotation curve and study the central...