Related papers: Revisiting Stephan's Quintet with deep optical ima…

The ~800 optically unseen (R>25.5) 24mum-selected sources in the complete Spitzer First Look Survey sample (Fadda et al. 2006) with F[24mum]>0.35 mJy are found to be very strongly clustered. If, as indicated by several lines of…

Recent work has shown that Milky Way-mass galaxies display an incredible range of stellar halo properties, yet the origin of this diversity is unclear. The nearby galaxy M81 $-$ currently interacting with M82 and NGC 3077 $-$ sheds unique…

Evolution of galaxies in dense environments can be affected by close encounters with neighbouring galaxies and interactions with the intracluster medium. Dwarf galaxies (dGs) are important as their low mass makes them more susceptible to…

The discovery of massive, high redshift galaxies with the James Webb Space Telescope (JWST) has been argued to challenge $\Lambda$CDM (cold dark matter): such systems would require extremely rare halos and baryon-to-stellar-mass conversion…

Hubble Space Telescope archive data are used to perform photometry of stars in seven fields at the center and periphery of the galaxy NGC2366. The variation of the number density of stars of various ages with galactocentric radius and along…

We explore the lowest mass limit that can be placed on the halo mass function in CDM using 28 strong gravitational lenses. For this purpose, we study an extreme model in which the halo mass function and mass-concentration relation follow…

The CXOCY J220132.8-320144 system consists of an edge-on spiral galaxy lensing a background quasar into two bright images. Previous efforts to constrain the mass distribution in the galaxy have suggested that at least one additional image…

Compact groups (CGs) of galaxies appear to be the densest galaxy systems containing a few luminous galaxies in close proximity to each other, which have a typical size of a few tens kilopacsec in observation. On the other hand, in the…

We simulate deep images from the Hubble Space Telescope (HST) using semi-empirical models of galaxy formation with only a few basic assumptions and parameters. We project our simulations all the way to the observational domain, adding…

We present a new technique for monitoring microlensing activity even in highly crowded fields, and use this technique to place limits on low-mass MACHOs in the haloes of M31 and the Galaxy. Unlike present Galactic microlensing surveys, we…

Microlensing surveys search for the transient brightening of a background star that is the signature of gravitational lensing by a foreground compact object. This technique is an elegant way to search for astrophysical candidates that might…

MAssive Compact Halo Objects such as brown dwarfs, Jupiters, and black holes are prime candidates to comprise the dark halo of our galaxy. Paczynski noted that objects (dubbed MACHOs) with masses in the range $10^{-6}M_\odot < M \simlt 100…

We develop an explicit model for the formation of the stellar halo from tidally disrupted, accreted dwarf satellites in the cold dark matter (CDM) framework, focusing on predictions testable with the Sloan Digital Sky Survey (SDSS) and…

The Star Formation Across Cosmic Time (SFACT) survey is a new narrowband survey designed to detect emission-line galaxies (ELGs) and quasi-stellar objects (QSOs) over a wide range of redshifts in discrete redshift windows. The survey…

The study of outer halo globular cluster (GC) populations can give insight into galaxy merging, globular cluster accretion and the origin of GCs. We use archival Subaru Hyper Suprime-Cam (HSC) data in concert with space-based GALEX, IRAC…

We have observed the closest known large, low surface brightness (LSB) galaxy, UGC 2302, with HST using WFPC2 and the F555W and F814W filters. UGC 2302 is a typical large LSB galaxy, and thus represents a good choice for detailed stellar…

The halos of galaxies preserve unique records of their formation histories. We carry out the first combined observational and theoretical study of phase-space halo substructure in an early-type galaxy: M87, the central galaxy in the Virgo…

We present a study on four new star clusters discovered in the halo of the intriguing dwarf irregular galaxy NGC 6822 from a wide field survey covering 3 deg x 3 deg area carried out with MegaCam at Canada-France-Hawaii Telescope (CFHT).…

Tidal interactions between massive galaxies and their satellites are fundamental processes in a Universe with L-Cold Dark Matter cosmology, redistributing material into faint features that preserve records of past galactic interactions.…

Galaxy systems with large magnitude gaps - defined as the difference in magnitude between the central galaxy and the brightest satellite in the central region - have been claimed to have earlier formation histories. In this study we measure…