Open AccessObserving baryonic dark matter with ALMA
Author(s) -
Kamaya Hideyuki,
Silk Joseph
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05853.x
Subject(s) - physics , astrophysics , galaxy , dipole , astronomy , dark matter , population , flux (metallurgy) , laser linewidth , sociology , laser , demography , materials science , quantum mechanics , optics , metallurgy
It has recently been argued that the unidentified SCUBA objects (USOs) are a thick disc population of free‐floating dense, compact galactic gas clumps at a temperature of about 7 K. The characteristic mass‐scale is constrained to be on the order of a Jupiter mass, and the size is about 10 au. A typical Galactic USO is located at a distance from the Sun of about 300 pc. We have calculated the molecular emission lines from these low‐temperature clouds. We consider three molecules: HD, LiH, and CO. HD is optically thin in the cloud, LiH is a molecule with a large electric dipole moment, and CO is an abundant molecule that is observed in dusty clouds. Our estimate for the typical object shows that LiH may be detectable by the future submillimetre (submm) array project, ALMA; its expected flux is at the mJy level and the linewidth is about 10 5 Hz . Although typical galactic USOs are chemically and dynamically transient, the younger USOs will be recognizable via LiH emission if about a hundred USOs are observed. If USOs are confirmed to be of galactic origin, the total baryonic budget will need to be reevaluated.