G. Medina

Discovery, Characterization, and Potential Origins of a Stream in the Stellar Halo of Nearby LMC-Mass Galaxy NGC 55

Benjamin N. Velguth, Burçin Mutlu-Pakdil, Erik Tollerud +33

We present a previously undetected stellar stream in the halo of the LMC-mass dwarf galaxy NGC 55 (2 Mpc), as part of an ongoing effort to characterize the stellar halos of LMC/SMC…

Discovery of the Distant, Ultra-Faint Milky Way Satellite Aquarius IV with the Vera C. Rubin Observatory Early Data Preview 2

William Cerny, Aashay Pai, Alex Drlica-Wagner +16

We present the discovery of Aquarius IV (Rubin J2201 $-$ 0234) -- the first ultra-faint Milky Way satellite to be identified using data from the Vera C. Rubin Observatory. This syste…

Characterizing the disruption of Böotes III: a missing link in the Galactic halo?

Jaclyn Jensen, Daniel A. Boyea, Alan W. McConnachie +14

The Böotes III (Boo3) dwarf galaxy has long been suspected of being the progenitor of Styx, a ~50°-long stellar stream that was simultaneously discovered in the same region of sky.…

Boötes III is a Tidally Disrupting Ultra-Faint Dwarf Galaxy on an Eccentric Polar Orbit

Ting S. Li, Denis Erkal, Andrew B. Pace +20

We present updated systemic properties of the ultra-faint dwarf galaxy Boötes III from the Southern Stellar Stream Spectroscopic Survey (S $^{5}$ ). We identify 21 high-probability mem…

Constraining the Galactic bar using the M92 stellar stream

Amanda Byström, Sergey E. Koposov, Ting. S. Li +42

Stellar streams are excellent probes of the gravitational potential in which they evolve. In the Milky Way (MW), globular cluster (GC) streams are routinely used to infer propertie…

Characterizing the GD-1 Stream with DESI DR2 Data: Thin Stream and Hot Cocoon

Emma Jarvis, Ting S. Li, Sergey E. Koposov +54

GD-1 is among the longest, coldest stellar streams in the Milky Way, making it an ideal target for probing dark matter substructure through dynamical heating. We present a catalog…

The DECam MAGIC Survey: Investigating the Jet Stellar Stream with Photometric Metallicities

H. Q. Do, A. Chiti, P. S. Ferguson +27

Stellar streams are dynamically fragile structures formed by the tidal disruption of dwarf galaxies and stellar clusters. These objects are valuable tracers of the gravitational po…

The velocity field of our Milky Way outer stellar halo based on DESI DR2

Songting Li, Wenting Wang, Sergey E. Koposov +53

Using 64,000 halo K giants from Dark Energy Spectroscopic Instrument (DESI) second Data Release (DR2), we decompose the Milky Way (MW) stellar halo between 3 and 160 kpc into metal…

The Kinematically Hot, Extremely Metal-Poor C-19 Stellar Stream in DESI DR2

Nasser Mohammed, Joseph Y. Tang, Ting S. Li +47

Stellar streams are the result of a host galaxy's gravitational potential tidally disrupting satellite dwarf galaxies and globular clusters (GCs), causing them to grow leading and…

Epicyclic Density Variations in the Indus Stellar Stream

Yong Yang, Geraint F. Lewis, Ting S. Li +12

Longitudinal density fluctuations observed in stellar streams can result from gravitational interactions with massive perturbers in the Milky Way, such as dark matter subhalos. Ana…

The DECam MAGIC Survey: Uncovering the Tidal Tails of the Crater II Dwarf Galaxy

Kaia R. Atzberger, Andrew B. Pace, Nitya Kallivayalil +27

Crater II (CraII), a large and low-density dwarf spheroidal galaxy, has unusual observed properties that are difficult to reproduce in cold dark matter simulations. Ongoing tidal d…

Signatures of a Tidally Induced Spiral Arm at the Anticenter of the Milky Way and a Kinematically Extended Anticenter Stream Using DESI DR2

Mika Lambert, Constance M. Rockosi, Sergey E. Koposov +46

Using the Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS), we examine the 6D space of the anticenter region of the stellar disk (150 $^{\circ}$ $<$ Galactic longitude…

The Milky Way stellar halo is twisted and doubly broken: insights from DESI DR2 Milky Way Survey observation

Songting Li, Wenting Wang, Sergey E. Koposov +45

Using K giants from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) Milky Way (MW) Survey, we measure the shape, orientation, radial profile, and d…

Chemodynamics of BoötesI with $S^{5}$ : Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints

Nathan R. Sandford, Ting S. Li, Sergey E. Koposov +14

We combine new spectroscopic observations of the ultra faint dwarf galaxy (UFD) Boötes I (Boo I) from the Southern Stellar Stream Spectroscopic Survey ( $S^{5}$ ) with $\sim$ 15 years…

The mass of the Milky Way from outer halo stars measured by DESI DR1

Gustavo E. Medina, Ting S. Li, Gwendolyn M. Eadie +50

As a benchmark for galaxy evolution and dark matter studies, the total mass of the Milky Way is a parameter of cosmological significance, and its value at large radii from the Gala…

Not-so-heavy metal(s): Chemical Abundances in the Ultra-faint Dwarf Galaxies Eridanus IV and Centaurus I

Mairéad E Heiger, Alexander P Ji, Ting S Li +18

We present detailed chemical abundances of the brightest star in each of the ultra-faint dwarf galaxies Eridanus IV and Centaurus I using high-resolution Magellan/MIKE spectroscopy…

astro-ph.GA2025★ 4 cited

A second-generation star in a relic dwarf galaxy

Anirudh Chiti, Vinicius M. Placco, Andrew B. Pace +22

Stars that contain only trace amounts of elements heavier than helium, referred to as having low "metallicity", preserve the chemical fingerprints of the first generation of stars…

The DECam MAGIC Survey: Spectroscopic Follow-up of the Most Metal-Poor Stars in the Distant Milky Way Halo

Vinicius M. Placco, Guilherme Limberg, Anirudh Chiti +21

In this work, we present high-resolution spectroscopic observations for six metal-poor stars with [Fe/H]<-3 (including one with [Fe/H]<-4), selected using narrow-band Ca II HK phot…

The NGC3109 Satellite System: The First Systematic Resolved Search for Dwarf Galaxies Around a SMC-mass Host

Amandine Doliva-Dolinsky, Burçin Mutlu-Pakdil, Denija Crnojević +38

We report the results of the deepest search to date for dwarf galaxies around NGC3109, a barred spiral galaxy with a mass similar to that of the Small Magellanic Cloud (SMC), using…

The DESI Y1 RR Lyrae catalog II: The metallicity dependency of pulsational properties, the shape of the RR Lyrae instability strip, and metal rich RR Lyrae

Gustavo E. Medina, Ting S. Li, C. Allende Prieto +39

RR Lyrae stars (RRLs) are valuable probes of both Milky Way assembly and stellar-evolution physics. Using a sample 6,240 RRLs obtained in the first year of the Dark Energy Spectros…

astro-ph.GA2025★ 4 cited

DELVE-DEEP Survey: The Faint Satellite System of NGC 55

Jonah Medoff, Burçin Mutlu-Pakdil, Jeffrey L. Carlin +24

We report the first comprehensive census of the satellite dwarf galaxies around NGC 55 ( $2.1$ Mpc) as a part of the DECam Local Volume Exploration DEEP (DELVE-DEEP) survey. NGC 55…

The DECam MAGIC Survey: A Wide-field Photometric Metallicity Study of the Sculptor Dwarf Spheroidal Galaxy

Fabrícia O. Barbosa, Anirudh Chiti, Guilherme Limberg +26

The metallicity distribution function and internal chemical variations of a galaxy are fundamental to understand its formation and assembly history. In this work, we analyze photom…

The DESI Y1 RR Lyrae catalog I: Empirical modeling of the cyclic variation of spectroscopic properties and a chemodynamical analysis of the outer halo

Gustavo E. Medina, Ting S. Li, Sergey E. Koposov +44

We present the catalog of RR Lyrae stars (RRLs) observed in the first year of operations of the Dark Energy Spectroscopic Instrument (DESI) survey. This catalog contains 6,240 RRLs…