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Title: New astrophysical bounds on ultralight axionlike particles

Motivated by tension between the predictions of ordinary cold dark matter (CDM) and observations at galactic scales, ultralight axionlike particles (ULALPs) with mass of the order 10 -22 eV have been proposed as an alternative CDM candidate. We consider cold and collisionless ULALPs produced in the early Universe by the vacuum realignment mechanism and constituting most of CDM. The ULALP fluid is commonly described by classical field equations. However, we show that, like QCD axions, the ULALPs thermalize by gravitational self-interactions and form a Bose-Einstein condensate, a quantum phenomenon. ULALPs, like QCD axions, explain the observational evidence for caustic rings of dark matter because they thermalize and go to the lowest energy state available to them. This is one of rigid rotation on the turnaround sphere. Here, by studying the heating effect of infalling ULALPs on galactic disk stars and the thickness of the nearby caustic ring as observed from a triangular feature in the infrared astronomical satellite map of our galactic disk, we obtain lower-mass bounds on the ULALP mass of order 10 -23 and 10 -20 eV, respectively.
Authors:
 [1] ;  [2] ;  [2] ;  [2]
  1. Univ. of Florida, Gainesville, FL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  2. Univ. of Florida, Gainesville, FL (United States)
Publication Date:
Report Number(s):
FERMILAB-PUB-17-047; arXiv:1701.04573
Journal ID: ISSN 2470-0010; PRVDAQ; 1509351; TRN: US1700849
Grant/Contract Number:
AC02-07CH11359; FG02-97ER41029; 2015-109
Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 95; Journal Issue: 4; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1350514
Alternate Identifier(s):
OSTI ID: 1345281