分类： 天文学 >> 天文学 提交时间： 2023-02-19
Andrew P. Cooper
Sergey E. Koposov
Carlos Allende Prieto
Christopher J. Manser
Namitha Kizhuprakkat
Adam D. Myers
Arjun Dey
Boris T. Gaensicke
Ting S. Li
Constance Rockosi
Monica Valluri
Joan Najita
Alis Deason
Anand Raichoor
Mei-Yu Wang
Yuan-Sen Ting
Bokyoung Kim
Andreia Carrillo
Wenting Wang
Leandro Beraldo e Silva
摘要： We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven million stars at Galactic latitudes |b|>20 degrees, with an inclusive target selection scheme focused on the thick disk and stellar halo. MWS will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100pc of the Sun, and horizontal branch stars. We summarize the potential of DESI to advance understanding of Galactic structure and stellar evolution. We introduce the final definitions of the main MWS target classes and estimate the number of stars in each class that will be observed. We describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. We use ~500,000 spectra of unique stellar targets from the DESI Survey Validation program (SV) to demonstrate that our pipelines can measure radial velocities to ~1 km/s and [Fe/H] accurate to ~0.2 dex for typical stars in our main sample. We find the stellar parameter distributions from ~100 sq. deg of SV observations with >90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
David J. Setton
Biprateep Dey
Gourav Khullar
Rachel Bezanson
Jeffrey A. Newman
Jessica N. Aguilar
Steven Ahlen
Brett H. Andrews
David Brooks
Axel de la Macorra
Arjun Dey
Sarah Eftekharzadeh
Andreu Font-Ribera
Satya Gontcho A Gontcho
Anthony Kremin
Stephanie Juneau
Martin Landriau
Aaron Meisner
Ramon Miquel
John Moustakas
摘要： We utilize $\sim17000$ bright Luminous Red Galaxies (LRGs) from the novel Dark Energy Spectroscopic Instrument Survey Validation spectroscopic sample, leveraging its deep ($\sim2.5$ hour/galaxy exposure time) spectra to characterize the contribution of recently quenched galaxies to the massive galaxy population at $0.41$) of our sample of recently quenched galaxies represents the largest spectroscopic sample of post-starburst galaxies at that epoch. At $0.411.2$) LRGs by measuring the fraction of stellar mass each galaxy formed in the Gyr before observation, $f_{\mathrm{1 Gyr}}$. Although galaxies with $f_{\mathrm{1 Gyr}}>0.1$ are rare at $z\sim0.4$ ($\lesssim 0.5\%$ of the population), by $z\sim0.8$ they constitute $\sim3\%$ of massive galaxies. Relaxing this threshold, we find that galaxies with $f_\mathrm{1 Gyr}>5\%$ constitute $\sim10\%$ of the massive galaxy population at $z\sim0.8$. We also identify a small but significant sample of galaxies at $z=1.1-1.3$ that formed with $f_{\mathrm{1 Gyr}}>50\%$, implying that they may be analogues to high-redshift quiescent galaxies that formed on similar timescales. Future analysis of this unprecedented sample promises to illuminate the physical mechanisms that drive the quenching of massive galaxies after cosmic noon.
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