分类： 天文学 >> 天文学 提交时间： 2023-02-19
David Martinez-Delgado
Andrew P. Cooper
Javier Roman
Annalisa Pillepich
Denis Erkal
Sarah Pearson
John Moustakas
Chervin F. P. Laporte
Seppo Laine
Mohammad Akhlaghi
Dustin Lang
Dmitry Makarov
Alejandro S. Borlaff
Giuseppe Donatiello
William J. Pearson
Juan Miro-Carretero
Jean-Charles Cuillandre
Helena Dominguez
Santi Roca-Fabrega
Carlos S. Frenk
摘要： Mergers and tidal interactions between massive galaxies and their dwarf satellites are a fundamental prediction of the Lambda-Cold Dark Matter cosmology. These events are thought to provide important observational diagnostics of nonlinear structure formation. Stellar streams in the Milky Way and Andromeda are spectacular evidence for ongoing satellite disruption. However, constructing a statistically meaningful sample of tidal streams beyond the Local Group has proven a daunting observational challenge, and the full potential for deepening our understanding of galaxy assembly using stellar streams has yet to be realised. Here we introduce the Stellar Stream Legacy Survey, a systematic imaging survey of tidal features associated with dwarf galaxy accretion around a sample of ~3100 nearby galaxies within z~0.02, including about 940 Milky Way analogues. Our survey exploits public deep imaging data from the DESI Legacy Imaging Surveys, which reach surface brightness as faint as ~29 mag/arcsec^2 in the r band. As a proof of concept of our survey, we report the detection and broad-band photometry of 24 new stellar streams in the local Universe. We discuss how these observations can yield new constraints on galaxy formation theory through comparison to mock observations from cosmological galaxy simulations. These tests will probe the present-day mass assembly rate of galaxies, the stellar populations and orbits of satellites, the growth of stellar halos and the resilience of stellar disks to satellite bombardment.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Adam D. Myers
John Moustakas
Stephen Bailey
Benjamin A. Weaver
Andrew P. Cooper
Jaime E. Forero-Romero
Bela Abolfathi
David M. Alexander
David Brooks
Edmond Chaussidon
Chia-Hsun Chuang
Kyle Dawson
Arjun Dey
Biprateep Dey
Govinda Dhungana
Peter Doel
Kevin Fanning
Enrique Gaztañaga
Satya Gontcho A Gontcho
Alma X. Gonzalez-Morales
摘要： In 2021 May, the Dark Energy Spectroscopic Instrument (DESI) began a 5 yr survey of approximately 50 million total extragalactic and Galactic targets. The primary DESI dark-time targets are emission line galaxies (ELGs), luminous red galaxies (LRGs) and quasars (QSOs). In bright time, DESI will focus on two surveys known as the Bright Galaxy Survey (BGS) and the Milky Way Survey (MWS). DESI also observes a selection of "secondary" targets for bespoke science goals. This paper gives an overview of the publicly available pipeline (desitarget) used to process targets for DESI observations. Highlights include details of the different DESI survey targeting phases, the targeting ID (TARGETID) used to define unique targets, the bitmasks used to indicate a particular type of target, the data model and structure of DESI targeting files, and examples of how to access and use the desitarget code base. This paper will also describe "supporting" DESI target classes, such as standard stars, sky locations, and random catalogs that mimic the angular selection function of DESI targets. The DESI target selection pipeline is complex and sizable; this paper attempts to summarize the most salient information required to understand and work with DESI targeting data.
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