Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron Romanowsky, Jean Brodie, Anna Ferr´E-Mateu, Adebusola Alabi, Duncan Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado
Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron Romanowsky, Jean Brodie, Anna Ferr´E-Mateu, Adebusola Alabi, Duncan Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado
Faculty Publications
Ultradiffuse galaxies (UDGs) are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ∼3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in …
Contribution Of Hi-Bearing Ultra-Diffuse Galaxies To The Cosmic Number Density Of Galaxies, M. Jones, E. Papastergis, V. Pandya, L. Leisman, Aaron J. Romanowsky, L. Yung, R. Somerville, E. Adams
Contribution Of Hi-Bearing Ultra-Diffuse Galaxies To The Cosmic Number Density Of Galaxies, M. Jones, E. Papastergis, V. Pandya, L. Leisman, Aaron J. Romanowsky, L. Yung, R. Somerville, E. Adams
Faculty Publications
We estimate the cosmic number density of the recently identified class of HI-bearing ultra-diffuse sources (HUDs) based on the completeness limits of the ALFALFA survey. These objects have HI masses approximately in the range 8.5 < logMHI∕M⊙ < 9.5, average r-band surface brightnesses fainter than 24 mag arcsec−2, half-light radii greater than 1.5 kpc, and are separated from neighbours by at least 350 kpc. In this work we demonstrate that they contribute at most ~6% of the population of HI-bearing dwarfs detected by ALFALFA (with similar HI masses), have a total cosmic number density of (1.5 ± 0.6) × 10−3 …
The Stellar Initial Mass Function In Early-Type Galaxies From Absorption Line Spectroscopy. Iii. Radial Gradients, Pieter Van Dokkum, Charlie Conroy, Alexa Villaume, Jean Brodie, Aaron Romanowsky
The Stellar Initial Mass Function In Early-Type Galaxies From Absorption Line Spectroscopy. Iii. Radial Gradients, Pieter Van Dokkum, Charlie Conroy, Alexa Villaume, Jean Brodie, Aaron Romanowsky
Faculty Research, Scholarly, and Creative Activity
No abstract provided.
Erratum: Global Properties Of ‘Ordinary’ Early-Type Galaxies: Photometry And Spectroscopy Of Stars And Globular Clusters In Ngc 4494, Caroline Foster, Lee Spitler, Aaron Romanowsky, Duncan Forbes, Vincenzo Pota, Kenji Bekki, Jay Strader, Robert Proctor, Jacob Arnold, Jean Brodie
Erratum: Global Properties Of ‘Ordinary’ Early-Type Galaxies: Photometry And Spectroscopy Of Stars And Globular Clusters In Ngc 4494, Caroline Foster, Lee Spitler, Aaron Romanowsky, Duncan Forbes, Vincenzo Pota, Kenji Bekki, Jay Strader, Robert Proctor, Jacob Arnold, Jean Brodie
Faculty Publications
This is an erratum to the paper entitled “Global properties of ‘ordinary’ early-type galaxies: photometry and spectroscopy of stars and globular clusters in NGC 4494”, published in MNRAS, 2011, 415, 3393.
New Spectroscopic Technique Based On Coaddition Of Surface Brightness Fluctuations: Ngc 4449 And Its Stellar Tidal Stream, Elisa Toloba, Puragra Guhathakurta, Aaron Romanowsky, Jean Brodie, David Martínez-Delgado, Jacob Arnold, Neel Ramachandran, Kuriakose Theakanath
New Spectroscopic Technique Based On Coaddition Of Surface Brightness Fluctuations: Ngc 4449 And Its Stellar Tidal Stream, Elisa Toloba, Puragra Guhathakurta, Aaron Romanowsky, Jean Brodie, David Martínez-Delgado, Jacob Arnold, Neel Ramachandran, Kuriakose Theakanath
Faculty Publications
No abstract provided.
The Sluggs Survey: A New Mask Design To Reconstruct The Stellar Populations And Kinematics Of Both Inner And Outer Galaxy Regions, Nicola Pastorello, Duncan Forbes, Adriano Poci, Aaron Romanowsky, Richard Mcdermid, Adebusola Alabi, Jean Brodie, Michele Cappellari, Vincenzo Pota, Caroline Foster
The Sluggs Survey: A New Mask Design To Reconstruct The Stellar Populations And Kinematics Of Both Inner And Outer Galaxy Regions, Nicola Pastorello, Duncan Forbes, Adriano Poci, Aaron Romanowsky, Richard Mcdermid, Adebusola Alabi, Jean Brodie, Michele Cappellari, Vincenzo Pota, Caroline Foster
Faculty Publications
Integral field unit spectrographs allow the 2D exploration of the kinematics and stellar populations of galaxies, although they are generally restricted to small fields-of-view. Using the large field-of-view of the DEIMOS multislit spectrograph on Keck and our Stellar Kinematics using Multiple Slits technique, we are able to extract sky-subtracted stellar light spectra to large galactocentric radii. Here, we present a new DEIMOS mask design named SuperSKiMS that explores large spatial scales without sacrificing high spatial sampling. We simulate a set of observations with such a mask design on the nearby galaxy NGC 1023, measuring stellar kinematics and metallicities out to …
The Sluggs Survey: Combining Stellar And Globular Cluster Metallicities In The Outer Regions Of Early-Type Galaxies, Nicola Pastorello, Duncan Forbes, Christopher Usher, Jean Brodie, Aaron Romanowsky, Jay Strader, Lee Spitler, Adebusola Alabi, Caroline Foster, Zachary Jennings, Sreeja Kartha, Vincenzo Pota
The Sluggs Survey: Combining Stellar And Globular Cluster Metallicities In The Outer Regions Of Early-Type Galaxies, Nicola Pastorello, Duncan Forbes, Christopher Usher, Jean Brodie, Aaron Romanowsky, Jay Strader, Lee Spitler, Adebusola Alabi, Caroline Foster, Zachary Jennings, Sreeja Kartha, Vincenzo Pota
Faculty Publications
The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using the DEep Imaging Multi-Object Spectrograph on the Keck, we have been able to measure the metallicities of the stellar and globular cluster components in 12 early-type galaxies out to more than 10Re. We find similar metallicity gradients for the metal-poor and metal-rich globular cluster subpopulations, suggesting a common formation process for the two subpopulations. This is in conflict with most current theoretical predictions, where the metal-poor globular clusters are thought to …
Detection Of A Distinct Metal-Poor Stellar Halo In The Early-Type Galaxy Ngc 3115*, Mark Peacock, Jay Strader, Aaron Romanowsky, Jean Brodie
Detection Of A Distinct Metal-Poor Stellar Halo In The Early-Type Galaxy Ngc 3115*, Mark Peacock, Jay Strader, Aaron Romanowsky, Jean Brodie
Faculty Publications
We present the resolved stellar populations in the inner and outer halo of the nearby lenticular galaxy NGC 3115. Using deep Hubble Space Telescope observations, we analyze stars 2 mag fainter than the tip of the red giant branch (TRGB). We study three fields along the minor axis of this galaxy, 19, 37, and 54 kpc from its center—corresponding to 7, 14, and 21 effective radii (re ). Even at these large galactocentric distances, all of the fields are dominated by a relatively enriched population, with the main peak in the metallicity distribution decreasing with radius from [Z/H] ~ –0.5 …
The Sluggs Survey: Globular Cluster Stellar Population Trends From Weak Absorption Lines In Stacked Spectra, Christopher Usher, Duncan Forbes, Jean Brodie, Aaron Romanowsky, Jay Strader, Charlie Conroy, Caroline Foster, Nicola Pastorello, Vincenzo Pota, Jacob Arnold
The Sluggs Survey: Globular Cluster Stellar Population Trends From Weak Absorption Lines In Stacked Spectra, Christopher Usher, Duncan Forbes, Jean Brodie, Aaron Romanowsky, Jay Strader, Charlie Conroy, Caroline Foster, Nicola Pastorello, Vincenzo Pota, Jacob Arnold
Faculty Publications
As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ∼90 Å−1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and …