Optical Counterparts to X-ray sources in LSST DP1

Abstract

We present a crossmatch between a combined catalog of X-ray sources and the Vera C. Rubin Observatory Data Preview 1 (DP1) to identify optical counterparts. The six fields targeted as part of DP1 include the Extended Chandra Deep Field South (E-CDF-S), the Euclid Deep Field South (EDF-S), the Fornax Dwarf Spheroidal Galaxy (Fornax dSph), 47 Tucanae (47 Tuc) and science validation fields with low galactic and ecliptic latitude (SV\_95\_-25 and SV\_38\_7, respectively). We find matches to 2314 of 3830 X-ray sources. We also compare our crossmatch to DP1 in the E-CDF-S field to previous efforts to identify optical counterparts. The probability of a chance coincidence match varies across each DP1 field, with overall high reliability in the E-CDF-S field, and lower proportion of high-reliability matches in the other fields. The majority of previously known sources that we detect are, unsurprisingly, active galaxies. We plot the X-ray-to-optical flux ratio against optical magnitude and color in an effort to identify Galactic accreting compact objects using a {\em Gaia} color threshold transformed to LSST $g$--$i$, but do not find any strong candidates in these primarily extragalactic counterparts. The DP1 dataset contains high-cadence photometry collected over a number of nights. We calculate the Stetson \( J \) variability index for each object under the hypothesis that X-ray counterparts tend to exhibit higher optical variability; however, the evidence is inconclusive whether our sample is more variable over DP1 timescales when compared to field objects.

14 pages, 8 figures

References in corpus (18)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• astroquery: An Astronomical Web-Querying Package in Python
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• The XMM-Newton serendipitous survey IX. The fourth XMM-Newton serendipitous source catalogue
• Absorption Properties and Evolution of Active Galactic Nuclei
• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The first XMM-Newton slew survey catalogue: XMMSL1
• Probabilistic Cross-Identification of Astronomical Sources
• The Million Quasars (Milliquas) Catalogue, v8
• Cataclysmic Variables from the Catalina Real-time Transient Survey
• Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. IX: The Ninth Year (2016-2017)
• A structure function analysis of VST-COSMOS AGN
• The Vera C. Rubin Observatory Data Preview 1
• Probabilistic Cross-Identification in Crowded Fields as an Assignment Problem
• Joint Modeling of Quasar Variability and Accretion Disk Reprocessing using Latent Stochastic Differential Equations

Cited by in corpus (1)

• A comprehensive search for high-velocity X-ray sources: New compact object binary candidates in the Gaia era