Identifying RR Lyrae Variable Stars in Six Years of the Dark Energy Survey

Abstract

We present a search for RR Lyrae stars using the full six-year data set from the Dark Energy Survey (DES) covering ~5,000 sq. deg. of the southern sky. Using a multi-stage multi-variate classification and light curve template-fitting scheme, we identify RR Lyrae candidates with a median of 35 observations per candidate. We detect 6,971 RR Lyrae candidates out to ~335 kpc, and we estimate that our sample is >70% complete at ~150 kpc. We find excellent agreement with other wide-area RR Lyrae catalogs and RR Lyrae studies targeting the Magellanic Clouds and other Milky Way satellite galaxies. We fit the smooth stellar halo density profile using a broken-power-law model with fixed halo flattening (q = 0.7), and we find strong evidence for a break at $R_0=32.1_{-0.9}^{+1.1}$ kpc with an inner slope of $n_1=-2.54_{-0.09}^{+0.09}$ and an outer slope of $n_2=-5.42_{-0.14}^{+0.13}$. We use our catalog to perform a search for Milky Way satellite galaxies with large sizes and low luminosities. Using a set of simulated satellite galaxies, we find that our RR Lyrae-based search is more sensitive than those using resolved stellar populations in the regime of large ($r_h>500$ pc), low-surface-brightness dwarf galaxies. A blind search for large, diffuse satellites yields three candidate substructures. The first can be confidently associated with the dwarf galaxy Eridanus II. The second has a similar distance and proper motion to the ultra-faint dwarf galaxy Tucana II but is separated by ~5 deg. The third is close in projection to the globular cluster NGC 1851 but is ~10 kpc more distant and appears to differ in proper motion.

arXiv comment34 pages, 20 figures, 9 tables. Updated to match published version. Data products are available at https://des.ncsa.illinois.edu/releases/other/y6-rrl

References in corpus (112)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Correcting for the Effects of Interstellar Extinction
• The observed properties of dwarf galaxies in and around the Local Group
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• The Dark Energy Camera
• Tracing Galaxy Formation with Stellar Halos I: Methods
• The Dark Energy Survey: more than dark energy - an overview
• Co-formation of the Galactic disc and the stellar halo
• The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
• The Field of Streams: Sagittarius and its Siblings
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
• Eight Ultra-faint Galaxy Candidates Discovered in Year Two of the Dark Energy Survey
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The Catalina Surveys Periodic Variable Star Catalog
• Variable Stars in Galactic Globular Clusters
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• Galaxia: a code to generate a synthetic survey of the Milky Way
• A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• Stellar Streams Discovered in the Dark Energy Survey
• The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration
• Substructure revealed by RR Lyraes in SDSS Stripe 82
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• The stellar halo of the Galaxy
• Probing the Outer Galactic halo with RR Lyrae from the Catalina Surveys
• The Dark Energy Survey Image Processing Pipeline
• The QUEST RR Lyrae Survey: Confirmation of the Clump at 50 kpc and Other Over-Densities in the Outer Halo
• Light Curve Templates and Galactic Distribution of RR Lyrae Stars from Sloan Digital Sky Survey Stripe 82
• How Lumpy is the Milky Way's Dark Matter Halo?
• The third data release of the Kilo-Degree Survey and associated data products
• On a new theoretical framework for RR Lyrae stars I: the metallicity dependence
• A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters
• The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2
• Broken and unbroken: the Milky Way and M31 stellar haloes
• Kinematics of the stellar halo and the mass distribution of the Milky Way using BHB stars
• The Star Formation & Chemical Evolution History of the Fornax Dwarf Spheroidal Galaxy
• Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1
• The Shape and Profile of the Milky Way Halo as Seen by the CFHT Legacy Survey
• Machine-Learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: the PS1 Sample
• The QUEST RR Lyrae Survey II: The Halo Overdensities in the First Catalog
• The cold veil of the Milky Way stellar halo
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• Piercing the Milky Way: an all-sky view of the Orphan Stream
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• Deep imaging of Eridanus II and its lone star cluster
• Discovery of $\sim$ 9,000 new RR Lyrae in the Southern Catalina Surveys
• Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc
• Forward Global Photometric Calibration of the Dark Energy Survey
• Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae stars in the Nearby Globular Cluster M4 (NGC 6121)
• Comparative performance of selected variability detection techniques in photometric time series
• On the Blazhko Effect in RR Lyrae Stars
• The information content in cold stellar streams
• Weak Galactic halo--dwarf spheroidal connection from RR Lyrae stars
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• First Results from the NOAO Survey of the Outer Limits of the Magellanic Clouds
• Proper motions of Milky Way Ultra-Faint satellites with $Gaia$ DR2 $\times$ DES DR1
• Fourteen candidate RR Lyrae star streams in the inner Galaxy
• Stellar streams around the Magellanic Clouds
• The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae
• Variable Stars in the Fornax Dwarf Galaxy
• Searches for New Milky Way Satellites from the First Two Years of Data of the Subaru/Hyper Suprime-Cam Survey: Discovery of Cetus~III
• Photometric Variability at the L/T Dwarf Boundary
• La Silla QUEST RR Lyrae Star Survey: Region I
• Birds of a Feather? Magellan/IMACS Spectroscopy of the Ultra-Faint Satellites Grus II, Tucana IV, and Tucana V
• Variable Stars in Local Group Galaxies. I: Tracing the Early Chemical Enrichment and Radial Gradients in the Sculptor dSph with RR Lyrae Stars
• Variable stars in Local Group Galaxies - II. Sculptor dSph
• The ACS LCID Project. II. Faint Variable Stars in the Isolated Dwarf Irregular Galaxy IC1613
• Finding, characterizing and classifying variable sources in multi-epoch sky surveys: QSOs and RR Lyrae in PS1 3$\pi$ data
• Full 5D characterisation of the Sagittarius stream with Gaia DR2 RR Lyrae
• On the use of field RR Lyrae as Galactic probes: I. The Oosterhoff dichotomy based on fundamental variables
• Search for RR Lyrae stars in DES ultra-faint systems: Grus I, Kim 2, Phoenix II, and Grus II
• Stacking the Invisibles: A Guided Search for Low-Luminosity Milky Way Satellites
• The Period-Luminosity Relation of RR Lyrae Stars in the SDSS Photometric System
• Exploring Halo Substructure with Giant Stars: The Nature of the Triangulum-Andromeda Stellar Features
• Discovery of distant RR Lyrae stars in the Milky Way using DECam
• Gaia Data Release 2: All-sky classification of high-amplitude pulsating stars
• Characterizing stellar halo populations II: The age gradient in blue horizontal-branch stars
• Probing the early chemical evolution of the Sculptor dSph with purely old stellar tracers
• Exploring the Very Extended Low Surface Brightness Stellar Populations of the Large Magellanic Cloud with SMASH
• The bursty star formation history of the Fornax dwarf spheroidal galaxy revealed with the HST
• The variable star population in Phoenix: coexistence of Anomalous and short-period Classical Cepheids, and detection of RR Lyrae variables
• Kinematics of the Palomar 5 stellar stream from RR Lyrae stars
• A skewer survey of the Galactic halo from deep CFHT and INT images
• Catalog of quasars from the Kilo-Degree Survey Data Release 3
• Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
• The morphology and structure of stellar populations in the Fornax dwarf spheroidal galaxy from Dark Energy Survey Data
• The ISLAnds Project III: Variable Stars in Six Andromeda Dwarf Spheroidal Galaxies
• Stellar metallicities from SkyMapper photometry I: A study of the Tucana II ultra-faint dwarf galaxy
• Gaia RR Lyrae Stars in Nearby Ultra-Faint Dwarf Satellite Galaxies
• Charting Unexplored Dwarf Galaxy Territory With RR Lyrae
• A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars
• RR Lyrae in XSTPS: The halo density profile in the North Galactic Cap
• Pan-STARRS1 variability of XMM-COSMOS AGN. I. Impact on photometric redshifts
• A Study of Quasar Selection in the Dark Energy Survey Supernova fields
• Group Finding in the Stellar Halo using Photometric Surveys: Current Sensitivity and Future Prospects
• Absolute Magnitudes and Colors of RR Lyrae stars in DECam Passbands from Photometry of the Globular Cluster M5
• The Araucaria Project: The distance to the Fornax Dwarf Galaxy from near-infrared photometry of RR Lyrae stars
• Identification of RR Lyrae stars in multiband, sparsely-sampled data from the Dark Energy Survey using template fitting and Random Forest classification
• Modelling the Milky Way. I -- Method and first results fitting the thick disk and halo with DES-Y3 data
• Variable Stars in Large Magellanic Cloud Globular Clusters III: Reticulum
• New views of the distant stellar halo
• A Magellanic origin for the Virgo substructure
• Photometric study of the SMCNOD using variable stars from the OGLE-IV survey

Cited by in corpus (19)

• $S^5$: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
• Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-Faint Dwarf Galaxy in the Constellation Pegasus
• RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3
• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• Variable stars in Local Group Galaxies -- V. The fast and early evolution of the low-mass Eridanus II dSph galaxy
• An extended stellar halo discovered in the Fornax dwarf spheroidal using Gaia EDR3
• Linking nearby stellar streams to more distant halo overdensities
• Stellar proper motions in the outskirts of classical dwarf spheroidal galaxies with Gaia EDR3
• On the Use of Field RR Lyrae as Galactic Probes. VI. Mixed mode RR Lyrae variables in Fornax and in nearby dwarf galaxies
• Ultracool dwarfs candidates based on six years of the Dark Energy Survey data
• Identifying RR Lyrae in the ZTF DR3 dataset
• RR Lyrae stars as probes of the outer Galactic halo: Chemical and kinematic analysis of a pilot sample
• VVV catalog of ab-type RR Lyrae in the inner Galactic bulge
• Mapping the Milky Way's stellar halo with 2D data
• RR Lyrae Stars In Stellar Streams with Gaia: The Escapers
• A search for distant, pulsating red giants in the southern halo
• Metallicity estimation of RR Lyrae stars from their I-band light curves
• photoD with Rubin's Data Preview 1: first stellar photometric distances and deficit of faint blue stars. Stellar distances with Rubin's DP1
• rrlfe: Software for Generating and Applying Metallicity Calibrations for RR Lyrae Variable Stars Across a Wide Range of Phases and Temperatures