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Still Missing Dark Matter: Kcwi High-Resolution Stellar Kinematics Of Ngc1052-Df2, Shany Danieli, Pieter van Dokkum, Charlie Conroy, Roberto Abraham, Aaron Romanowsky 2019 Yale University

Still Missing Dark Matter: Kcwi High-Resolution Stellar Kinematics Of Ngc1052-Df2, Shany Danieli, Pieter Van Dokkum, Charlie Conroy, Roberto Abraham, Aaron Romanowsky

Faculty Publications

The velocity dispersion of the ultra diffuse galaxy NGC1052-DF2 was found to be σgc = 7.8 +5.2/-2.2 km s−1, much lower than expected from the stellar mass–halo mass relation and nearly identical to the expected value from the stellar mass alone. This result was based on the radial velocities of 10 luminous globular clusters that were assumed to be associated with the galaxy. A more precise measurement is possible from high-resolution spectroscopy of the diffuse stellar light. Here we present an integrated spectrum of the diffuse light of NGC1052-DF2 obtained with the Keck Cosmic Web ...


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 2019 University of California Observatories

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 ...


Still Missing Dark Matter: Kcwi High-Resolution Stellar Kinematics Of Ngc1052-Df2, Shany Danieli, Pieter van Dokkum, Charlie Conroy, Roberto Abraham, Aaron J. Romanowsky 2019 Yale University

Still Missing Dark Matter: Kcwi High-Resolution Stellar Kinematics Of Ngc1052-Df2, Shany Danieli, Pieter Van Dokkum, Charlie Conroy, Roberto Abraham, Aaron J. Romanowsky

Aaron J. Romanowsky

The velocity dispersion of the ultra diffuse galaxy NGC1052-DF2 was found to be σgc = 7.8 +5.2/-2.2 km s−1, much lower than expected from the stellar mass–halo mass relation and nearly identical to the expected value from the stellar mass alone. This result was based on the radial velocities of 10 luminous globular clusters that were assumed to be associated with the galaxy. A more precise measurement is possible from high-resolution spectroscopy of the diffuse stellar light. Here we present an integrated spectrum of the diffuse light of NGC1052-DF2 obtained with the Keck Cosmic Web ...


Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron J. Romanowsky, Jean P. Brodie, Anna Ferr´e-Mateu, Adebusola Alabi, Duncan A. Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado 2019 University of California Observatories

Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron J. Romanowsky, Jean P. Brodie, Anna Ferr´E-Mateu, Adebusola Alabi, Duncan A. Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado

Aaron J. Romanowsky

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 ...


A Second Galaxy Missing Dark Matter In The Ngc 1052 Group, Pieter van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky 2019 Yale University

A Second Galaxy Missing Dark Matter In The Ngc 1052 Group, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky

Faculty Publications

The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf = 19.9 +/- 2.8 Mpc; and also has a population of luminous globular clusters extending out to >7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution Imaging ...


Multiple Spiral Arms In The Disk Around Intermediate-Mass Binary Hd 34700a, John D. Monnier, Tim Harries, Jaehan Bae, Benjamin R. Setterholm, Anna Laws, Alicia Aarnio, Fred C. Adams, Sean Andrews, Nuria Calvet, Catherine Espaillat, Lee Hartmann, Stefan Kraus, Melissa McClure, Chris Miller, Rebecca Oppenheimer, David Wilner, Zhaohuan Zhu 2019 The University Of Michigan

Multiple Spiral Arms In The Disk Around Intermediate-Mass Binary Hd 34700a, John D. Monnier, Tim Harries, Jaehan Bae, Benjamin R. Setterholm, Anna Laws, Alicia Aarnio, Fred C. Adams, Sean Andrews, Nuria Calvet, Catherine Espaillat, Lee Hartmann, Stefan Kraus, Melissa Mcclure, Chris Miller, Rebecca Oppenheimer, David Wilner, Zhaohuan Zhu

Physics & Astronomy Faculty Publications

We present the first images of the transition disk around the close binary system HD 34700A in polarized scattered light using the Gemini Planet Imager instrument on Gemini South. The J and H band images reveal multiple spiral-arm structures outside a large (R = 0.49" = 175 au) cavity along with a bluish spiral structure inside the cavity. The cavity wall shows a strong discontinuity and we clearly see significant non-azimuthal polarization Uphi consistent with multiple scattering within a disk at an inferred inclination ~42deg. Radiative transfer modeling along with a new Gaia distance suggest HD 37400A is a young (~5 ...


The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier 2019 University of Kentucky

The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier

Theses and Dissertations--Physics and Astronomy

A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated galaxies ...


The Non-Linear Dynamics Of Barred Galaxy Evolution In Lcdm, Michael Petersen 2019 University of Massachusetts Amherst

The Non-Linear Dynamics Of Barred Galaxy Evolution In Lcdm, Michael Petersen

Doctoral Dissertations

The study of barred galaxy dynamics has had many successes explaining observed phenomena in barred galaxies both locally and distant, including our own Milky Way, a barred galaxy. However, the majority of this knowledge arises from either (a) analytic linear theory, which by definition cannot inform nonlinear processes, or (b) simulations which are subject to an unconstrained host of evolutionary mechanisms, including `real' dynamical processes and `artificial' numerical processes, and are thus difficult to interpret. This work chooses a path which attempts to take the best of both techniques, employing n-body simulations in the Lambda cold dark matter paradigm designed ...


Finding Obscure Black Hole Growth Via Spectral Energy Distribution Modeling, Randall K. Chan 2019 Colby College

Finding Obscure Black Hole Growth Via Spectral Energy Distribution Modeling, Randall K. Chan

Honors Theses

An active galactic nucleus (AGN) occurs when the supermassive black hole at the center of the galaxy starts to grow. We still currently do not know what triggers AGN. Theories suggest that galaxy mergers could trigger AGNs, but past research has not been able to find a correlation between x-ray detected AGNs and disturbed galaxies. The present research looks specifically at AGN not detected in the x-ray, or obscured AGN. Using a newly updated IDL code, FAST, we were able to identify potential obscured AGN through spectral energy distribution (SED) modeling. We found a total of 526 obscured AGN in ...


Multiwavelength, Machine Learning, And Parallax Studies Of X-Ray Binaries In Three Local Group Galaxies, Robin Arnason 2018 The University of Western Ontario

Multiwavelength, Machine Learning, And Parallax Studies Of X-Ray Binaries In Three Local Group Galaxies, Robin Arnason

Electronic Thesis and Dissertation Repository

X-ray binary stars are rare systems consisting of a black hole or neutron star and a main-sequence companion star. They are useful probes of galaxy properties and interesting laboratories for extreme physical conditions. In this thesis, I investigated the X-ray binary population of three galaxies in the Local Group.

The Sculptor Dwarf Spheroidal Galaxy offers the chance to study a primordial low-mass X-ray binary (LMXB) population in an isolated, low-metallicity environment. Combining X-ray, optical, and infrared observations, I have studied nine previously-identified and discovered four additional LMXB candidates in this galaxy. Of these candidates, all but one are either background ...


Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy, David Martínez-Delgado, Eva Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio Carballo-Bello, Dmitry Makarov, Michael Beasley, Giuseppe Donatiello, Martha Haynes, Duncan Forbes, Aaron Romanowsky 2018 Universität Heidelberg

Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy, David Martínez-Delgado, Eva Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio Carballo-Bello, Dmitry Makarov, Michael Beasley, Giuseppe Donatiello, Martha Haynes, Duncan Forbes, Aaron Romanowsky

Faculty Publications

Context. It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies, both satellite and isolated, in the Local Volume.Aims. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low-surface-brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (β And) in a deep image taken with an amateur telescope.Methods ...


Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy, David Martínez-Delgado, Eva K. Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio A. Carballo-Bello, Dmitry Makarov, Michael A. Beasley, Giuseppe Donatiello, Martha P. Haynes, Duncan A. Forbes, Aaron J. Romanowsky 2018 Universität Heidelberg

Mirach’S Goblin: Discovery Of A Dwarf Spheroidal Galaxy Behind The Andromeda Galaxy, David Martínez-Delgado, Eva K. Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio A. Carballo-Bello, Dmitry Makarov, Michael A. Beasley, Giuseppe Donatiello, Martha P. Haynes, Duncan A. Forbes, Aaron J. Romanowsky

Aaron J. Romanowsky

Context. It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies, both satellite and isolated, in the Local Volume.

Aims. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low-surface-brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (β And) in a deep image taken with an amateur telescope.

Methods ...


Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges, S. Michael Fall, Aaron Romanowsky 2018 Space Telescope Science Institute

Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges, S. Michael Fall, Aaron Romanowsky

Faculty Publications

We show that the stellar specific angular momentum j, mass M, and bulge fraction of normal galaxies of all morphological types are consistent with a simple model based on a linear superposition of independent disks and bulges. In this model, disks and bulges follow scaling relations of the form and with but offset from each other by a factor of 8 ± 2 over the mass range . Separate fits for disks and bulges alone give and , respectively. This model correctly predicts that galaxies follow a curved 2D surface in the 3D space of , , and . We find no statistically significant indication that ...


Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges, S. Michael Fall, Aaron J. Romanowsky 2018 Space Telescope Science Institute

Angular Momentum And Galaxy Formation Revisited: Scaling Relations For Disks And Bulges, S. Michael Fall, Aaron J. Romanowsky

Aaron J. Romanowsky

We show that the stellar specific angular momentum j, mass M, and bulge fraction  of normal galaxies of all morphological types are consistent with a simple model based on a linear superposition of independent disks and bulges. In this model, disks and bulges follow scaling relations of the form  and  with  but offset from each other by a factor of 8 ± 2 over the mass range . Separate fits for disks and bulges alone give  and , respectively. This model correctly predicts that galaxies follow a curved 2D surface in the 3D space of , and . We find no statistically significant indication that ...


The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258, Yotam Cohen, Pieter van Dokkum, Shany Danieli, Aaron Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. Diederik Kruijssen, Charlie Conroy, Asher Wasserman 2018 Yale University

The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258, Yotam Cohen, Pieter Van Dokkum, Shany Danieli, Aaron Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. Diederik Kruijssen, Charlie Conroy, Asher Wasserman

Faculty Publications

We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging of 23 very low surface brightness (μ e,V ~ 25–27.5) galaxies detected in the fields of four nearby galaxy groups. These objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array. Seven are newly identified, while most of the others had been seen previously in visual surveys of deep photographic plates and more recent surveys. Few have previously been studied in detail. From the ACS images, we measure distances to the galaxies using both the tip of the red giant branch method and the ...


The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258, Yotam Cohen, Pieter van Dokkum, Shany Danieli, Aaron J. Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. M. Diederik Kruijssen, Charlie Conroy, Asher Wasserman 2018 Yale University

The Dragonfly Nearby Galaxies Survey. V. Hst/Acs Observations Of 23 Low Surface Brightness Objects In The Fields Of Ngc 1052, Ngc 1084, M96, And Ngc 4258, Yotam Cohen, Pieter Van Dokkum, Shany Danieli, Aaron J. Romanowsky, Roberto Abraham, Allison Merritt, Jielai Zhang, Lamiya Mowla, J. M. Diederik Kruijssen, Charlie Conroy, Asher Wasserman

Aaron J. Romanowsky

We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging of 23 very low surface brightness (μ e,V  ~ 25–27.5) galaxies detected in the fields of four nearby galaxy groups. These objects were selected from deep optical imaging obtained with the Dragonfly Telephoto Array. Seven are newly identified, while most of the others had been seen previously in visual surveys of deep photographic plates and more recent surveys. Few have previously been studied in detail. From the ACS images, we measure distances to the galaxies using both the tip of the red giant branch method and the ...


Dance Of Two Supermassive Binary Black Holes, Karishma Bansal 2018 University of New Mexico

Dance Of Two Supermassive Binary Black Holes, Karishma Bansal

Shared Knowledge Conference

Black holes exist in a various range of masses ranging from stellar mass (~ 10 Solar Mass) to Supermassive black holes (SMBHs, million to billion Solar Mass). It is expected that as the separation between the black holes decreases, emission of gravitational waves will grow stronger, which makes binary black holes one of the most promising sources for gravitational radiation detection. Gravitational waves from merging stellar-mass black holes have recently been discovered by LIGO; however, we are yet to detect them from binary SMBHs. These massive black holes reside at the heart of most of the galaxies and when two such ...


Studying The Potential Of The [Oii] Emission Line As A Surrogate For Stellar Velocity Dispersion In Active Galactic Nuclei, Edward F. Donohue 2018 California Polytechnic State University, San Luis Obispo

Studying The Potential Of The [Oii] Emission Line As A Surrogate For Stellar Velocity Dispersion In Active Galactic Nuclei, Edward F. Donohue

Physics

We study the emission profiles of 80 active galaxies to find a surrogate for stellar velocity dispersion. We focus on the width of the emission line of once ionized oxygen, [OII], and compare our results to previous work that used [OIII]. In previous research, [OIII] was found to be a good candidate for a surrogate for stellar velocity dispersion, but analysis of the line was complicated by the presence of wings caused by gas infall and outflow in the region. Emission lines with lower ionization levels, like [OII], are known to have less artificial line-broadening from wings. The study of ...


The Extended Planetary Nebula Spectrograph (Epn.S) Early-Type Galaxy Survey: The Kinematic Diversity Of Stellar Halos And The Relation Between Halo Transition Scale And Stellar Mass, C. Pulsoni, O. Gerhard, M. Arnaboldi, L. Coccato, A. Longobardi, N. R. Napolitano, E. Moylan, C. Narayan, V. Gupta, A. Burkert, M. Capaccioli, A. L. Chies-Santos, A. Cortesi, K. C. Freeman, K. Kuijken, M. R. Merrifield, Aaron J. Romanowsky, C. Tortora 2018 Max Planck Institute for Extraterrestrial Physics

The Extended Planetary Nebula Spectrograph (Epn.S) Early-Type Galaxy Survey: The Kinematic Diversity Of Stellar Halos And The Relation Between Halo Transition Scale And Stellar Mass, C. Pulsoni, O. Gerhard, M. Arnaboldi, L. Coccato, A. Longobardi, N. R. Napolitano, E. Moylan, C. Narayan, V. Gupta, A. Burkert, M. Capaccioli, A. L. Chies-Santos, A. Cortesi, K. C. Freeman, K. Kuijken, M. R. Merrifield, Aaron J. Romanowsky, C. Tortora

Aaron J. Romanowsky

Context. In the hierarchical two-phase formation scenario, the halos of early type galaxies (ETGs) are expected to have different physical properties from the galaxies’ central regions.

Aims. The ePN.S survey characterizes the kinematic properties of ETG halos using planetary nebulae (PNe) as tracers, overcoming the limitations of absorption line spectroscopy at low surface brightness.

Methods. We present two-dimensional velocity and velocity dispersion fields for 33 ETGs, including fast (FRs) and slow rotators (SRs). The velocity fields were reconstructed from the measured PN velocities using an adaptive kernel procedure validated with simulations, and extend to a median of 5.6 ...


Wide-Field Kinematics Of Globular Clusters In The Leo I Group (Corrigendum), G. Bergond, S. Zepf, Aaron Romanowsky, R. Sharples, K. Rhode 2018 Michigan State University

Wide-Field Kinematics Of Globular Clusters In The Leo I Group (Corrigendum), G. Bergond, S. Zepf, Aaron Romanowsky, R. Sharples, K. Rhode

Faculty Publications

No abstract provided.


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