分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hanyu Zhang
Lado Samushia
David Brooks
Axel de la Macorra
Peter Doel
Enrique Gaztañaga
Satya Gontcho A Gontcho
Klaus Honscheid
Robert Kehoe
Theodore Kisner
Aaron Meisner
Claire Poppett
Michael Schubnell
Gregory Tarle
Kai Zhang
Hu Zou
摘要： We investigate using three-point statistics in constraining the galaxy-halo connection. We show that for some galaxy samples, the constraints on the halo occupation distribution parameters are dominated by the three-point function signal (over its two-point counterpart). We demonstrate this on mock catalogs corresponding to the Luminous Red Galaxies (LRGs), Emission-Line Galaxies (ELG), and quasars (QSOs) targeted by the Dark Energy Spectroscopic Instrument (DESI) Survey. The projected three-point function for triangle sides less up to 20$h^{-1}$ Mpc measured from a cubic Gpc of data can constrain the characteristic minimum mass of the LRGs with a precision of $0.46$ %. For comparison, similar constraints from the projected two-point function are $1.55$ %. The improvements for the ELGs and QSOs targets are more modest. In the case of the QSOs it is caused by the high shot-noise of the sample, and in the case of the ELGs, this is caused by the range of halo masses of the host halos. The most time-consuming part of our pipeline is the measurement of the three-point functions. We adopt a tabulation method, proposed in earlier works for the two-point function, to reduce significantly the required compute time for the three-point analysis.
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.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Samantha Youles
Julian E. Bautista
Andreu Font-Ribera
David Bacon
James Rich
David Brooks
Tamara M. Davis
Kyle Dawson
Govinda Dhungana
Peter Doel
Kevin Fanning
Enrique Gaztañaga
Satya Gontcho A Gontcho
Alma X. Gonzalez-Morales
Julien Guy
Klaus Honscheid
Vid Iršič
Robert Kehoe
David Kirkby
Theodore Kisner
摘要： Using synthetic Lyman-$\alpha$ forests from the Dark Energy Spectroscopic Instrument (DESI) survey, we present a study of the impact of errors in the estimation of quasar redshift on the Lyman-$\alpha$ correlation functions. Estimates of quasar redshift have large uncertainties of a few hundred $\text{km s}^{-1}\,$ due to the broadness of the emission lines and the intrinsic shifts from other emission lines. We inject Gaussian random redshift errors into the mock quasar catalogues, and measure the auto-correlation and the Lyman-$\alpha$-quasar cross-correlation functions. We find a smearing of the BAO feature in the radial direction, but changes in the peak position are negligible. However, we see a significant unphysical correlation for small separations transverse to the line of sight which increases with the amplitude of the redshift errors. We interpret this contamination as a result of the broadening of emission lines in the measured mean continuum, caused by quasar redshift errors, combined with the unrealistically strong clustering of the simulated quasars on small scales.
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