Discovery of Two Small High-Velocity Compact Clouds in the Central 10 Parsecs of Our Galaxy

Abstract

We discovered two small high-velocity compact clouds (HVCCs) in HCN J=4-3 and J=3-2 maps of the central 20 pc of our Galaxy. Both HVCCs have broad velocity widths (∆V 40 km s −1 ) and compact sizes (d ∼ 1 pc), and originate from the dense molecular clouds in the position-velocity space. One of them has a faint counterpart in a Paschen-α image. Their spatial structure, kinematics, and absence of luminous stellar object are compatible with the notion that each of the small HVCCs is driven by the plunge of an invisible compact object into a molecular cloud. Such objects are most likely inactive, isolated black holes.

Looking at cosmic near-infrared background radiation anisotropies

“…PBHs in the mass range of ∼ 10 − 100M ⊙ appear allowed by the available observational data (see discussion in e.g. Carr et al, 2016) and the required abundance would appear in broad agreement with recently claimed abundance of quiescent black hole X-ray binaries in our Galaxy (Tetarenko et al, 2016) and possibly also with the observations of high-velocity clouds near the Galactic Center driven by inactive BHs rapidly plunging into molecular clouds Yamada et al, 2017). The mass range also is within the cosmological horizon at ∼ 0.01 − 0.1 GeV when various mechanisms for generating PBHs in the early Universe operate (e.g.…”

“…At the same time the excess CIB of ∼ 1nW/m 2 /sr around 3µm requires comoving density of CIB photons at n CIB ∼ 6 × 10 −4 cm −3 . Thus the sources producing the two together should have n CXB ((1 + z)keV)/n CIB (3/(1 + z)µm) < ∼ 6.6 × 10 −7 requiring the X/O ratio (defined as the logarithmic slope from 0.25µm to 2 keV, Tananbaum et al (1979)) α X/O < −2. Kashlinsky et al (2015b).…”