The DESI Y1 RR Lyrae catalog I: Empirical modeling of the cyclic variation of spectroscopic properties and a chemodynamical analysis of the outer halo

Journal Article · Wed Apr 02 20:00:00 EDT 2025 · No journal information

DOI:https://doi.org/10.48550/arXiv.2504.02924· OSTI ID:2564446

Medina, Gustavo E. ^[1]; Li, Ting S. ^[1]; Koposov, Sergey E. ^[2]; Riley, A. H. ^[3]; Beraldo e. Silva, L. ^[4]; Valluri, M. ^[5]; Wang, W. ^[6]; Byström, A. ^[7]; Gnedin, O. Y. ^[8]; Carlberg, R. G. ^[9]; Kizhuprakkat, N. ^[10]; Weaver, B. A. ^[11]; Aguilar, J. ^[12]; Ahlen, S. ^[13]; Bianchi, D. ^[14]; Brooks, D. ^[15]; Claybaugh, T. ^[12]; Cooper, A. P. ^[10]; de la Macorra, A. ^[16]; Dey, A. ^[11] ; Doel, P. ^[15]; Font-Ribera, A. ^[17]; Forero-Romero, J. E. ^[18]; Gaztañaga, E. ^[19]; Gontcho A. Gontcho, S. ^[12]; Gutierrez, G. ^[20]; Guy, J. ^[12]; Honscheid, K. ^[21]; Ishak, M. ^[22]; Kisner, T. ^[12]; Landriau, M. ^[12]; Le Guillou, L. ^[23]; Meisner, A. ^[11]; Miquel, R. ^[24]; Myers, A. D. ^[25]; Nadathur, S. ^[26]; Poppett, C. ^[27]; Prada, F. ^[28]; Pérez-Ràfols, I. ^[29]; Rossi, G. ^[30]; Sanchez, E. ^[31]; Seo, H. ^[32]; Sprayberry, D. ^[11]; Tarlé, G. ^[8]; Wechsler, R. H. ^[33]; Zhou, R. ^[12]; Zou, H. ^[34]

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1. U. Toronto, Dunlap Inst. Astron. Astrophys.; Toronto U., Astron. Dept.
2. Edinburgh U., Inst. Astron.; Cambridge U., Inst. of Astron.
3. Durham U., ICC
4. U. Michigan, Dept. Astron.; Arizona U., Astron. Dept. - Steward Observ.
5. U. Michigan, Dept. Astron.; Michigan U.; KEK, Tsukuba; Hiroshima Shudo U.
6. Shanghai Jiaotong U.; Shanghai Jiao Tong U.
7. Edinburgh U., Inst. Astron.
8. Michigan U.; KEK, Tsukuba; Hiroshima Shudo U.
9. Toronto U., Astron. Dept.
10. Taiwan, Natl. Tsing Hua U.
11. Natl. Solar Observ., Tucson
12. LBL, Berkeley
13. Boston U.
14. Milan U.; Brera Observ.
15. University Coll. London
16. UNAM, Mexico
17. Barcelona, IFAE
18. Andes U., Bogota
19. Barcelona, IEEC; Portsmouth U., ICG; ICE, Bellaterra
20. Fermilab
21. Chicago U., KICP; Ohio State U.
22. U. Texas, Dallas
23. LPNHE, Paris
24. ICREA, Barcelona; Barcelona, IFAE
25. Wyoming U.
26. Portsmouth U., ICG
27. LBL, Berkeley; UC, Berkeley (main); UC, Berkeley, Math. Dept.
28. Granada U., Theor. Phys. Astrophys.
29. Barcelona, Polytechnic U.
30. Sejong U.
31. Madrid, CIEMAT
32. Ohio U., Athens
33. KIPAC, Menlo Park; Stanford U., Phys. Dept.; SLAC
34. Beijing Observ.

We present the catalog of RR Lyrae stars observed in the first year of operations of the Dark Energy Spectroscopic Instrument (DESI) survey. This catalog contains 6,240 RR Lyrae stars out to $$\sim100$$ kpc from the Galactic center and over 12,000 individual epochs with homogeneously-derived stellar atmospheric parameters. We introduce a novel methodology to model the cyclical variation of the spectroscopic properties of RR Lyrae from single-epoch measurements. We employ this method to infer the radial velocity and effective temperature variation of fundamental mode and first-overtone RR Lyrae stars and to determine their systemic velocities and mean temperatures. For fundamental mode pulsators, we obtain radial velocity curves with amplitudes of $$\sim$$30--50 km s$$^{-1}$$ and effective temperature curves with 300--1,000 K variations, whereas for first-overtone pulsators these amplitudes are $$\sim20$$ km s$$^{-1}$$ and $$\sim 600$$ K, respectively. We use our sample to study the metallicity distribution of the halo and its dependence on Galactocentric distance ($$R_{\rm GC}$$). Using a radius-dependent mixture model, we split the data into chemodynamically distinct components and find that our inner halo sample ($$R_{\rm GC}\lesssim50$$ kpc) is predominantly composed of stars with [Fe/H] $$\sim-1.5$$ dex and largely radial orbits (with an anisotropy parameter $$\beta\sim0.94$$), that we associate with the Gaia-Sausage-Enceladus merger event. Stars in the outer halo field exhibit a broader and more metal-poor [Fe/H] distribution with more circular orbits ($$\beta\sim0.39$$). The metallicity gradient of the metal-rich and the metal-poor components is found to be $0.005$ and $0.010$ dex kpc$$^{-1}$$, respectively. Our catalog highlights DESI's tantalizing potential for studying the Milky Way and the pulsation properties of RR Lyrae stars in the era of large spectroscopic surveys.

• Research Organization: Shanghai Jiaotong U.; LPNHE, Paris; U. Toronto, Dunlap Inst. Astron. Astrophys.; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Durham U., ICC; Michigan U.; Wyoming U.; Stanford U., Phys. Dept.; ICE, Bellaterra; Ohio U., Athens; Milan U.; Barcelona, IEEC; KEK, Tsukuba; Barcelona, Polytechnic U.; Hiroshima Shudo U.; Madrid, CIEMAT; Beijing Observ.; Ohio State U.; UC, Berkeley (main); Natl. Solar Observ., Tucson; Shanghai Jiao Tong U.; ICREA, Barcelona; Brera Observ.; University Coll. London; UNAM, Mexico; Andes U., Bogota; U. Michigan, Dept. Astron.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Sejong U.; U. Texas, Dallas; Arizona U., Astron. Dept. - Steward Observ.; Boston U.; Barcelona, IFAE; Taiwan, Natl. Tsing Hua U.; Edinburgh U., Inst. Astron.; Toronto U., Astron. Dept.; UC, Berkeley, Math. Dept.; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Granada U., Theor. Phys. Astrophys.; Portsmouth U., ICG; Cambridge U., Inst. of Astron.; Chicago U., KICP
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 2564446
• Report Number(s): FERMILAB-PUB-25-0289-PPD; oai:inspirehep.net:2914867; arXiv:2504.02924
• Journal Information: No journal information, Journal Name: No journal information
• Country of Publication: United States
• Language: English

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79 ASTRONOMY AND ASTROPHYSICS