Abstract
ABSTRACT Soon after the recent first ever detection of gravitational waves from merging black holes it has been suggested that their origin is primordial. Appealingly, a sufficient number of primordial black holes (PBHs) could also partially or entirely constitute the dark matter (DM) in our Universe. However, recent studies on PBHs in ultra-faint dwarf galaxies (UFDGs) suggest that they would dynamically heat up the stellar component due to two-body relaxation processes. From the comparison with the observed stellar velocity dispersions and the stellar half-light radii, it was claimed that only PBHs with masses $\lesssim 10\, {\rm M}_\odot$ can significantly contribute to the DM. In this work, we improve the latter constraints by considering the largest observational sample of UFDGs and by allowing the PBH masses to follow an extended (lognormal) distribution. By means of collisional Fokker–Planck simulations, we explore a wide parameter space of UFDGs containing PBHs. The analysis of the half-light radii and velocity dispersions resulting from the simulations leads to three general findings that exclude PBHs with masses $\sim \mathcal {O}(1\operatorname{-}100)\, {\rm M}_\odot {}$ from constituting all of the DM: (i) we identify a critical sub-sample of UFDGs that only allows for $\sim \mathcal {O}(1)\, {\rm M}_\odot$ PBH masses; (ii) for any PBH mass, there is an UFDG in our sample that disfavours it; (iii) the spatial extensions of a majority of simulated UFDGs containing PBHs are too large to match the observed.
Highlights
E l = +31◦ in several molecular transitions, including 13CO (2 – 1) and C18O (2 – 1), probing the T moderately dense (∼103 cm−3) component of the interstellar medium
Observations of nearby spiral galaxies have I revealed a tight correlation between dense molecular gas and R enhancements of star formation activity within spiral arms clouds (GMCs) and investigate their properties with respect to their star formation activity and their Galactic distribution (Duarte-Cabral et al submitted; hereafter Paper III); and we investigate the dense gas fraction and star formation efficiency as a function of Galactic position (Urquhart et al submitted; hereafter Paper IV)
We provide data cubes covering these transitions as part of the DR1, where the spectra have been smoothed to 0.5 km s−1 velocity resolution in order to increase the signalto-noise ratio
Summary
Over the last few decades, many systematic continuum surveys of the Galactic plane have been carried out over the full electromagnetic spectrum, from the infrared (e.g. GLIMPSE, Churchwell et al 2009, MIPSGAL, Carey et al 2009, Hi-GAL, Molinari et al 2010) to the (sub-)millimetre (ATLASGAL, Schuller et al 2009, BGPS, Aguirre et al 2011, JPS, Moore et al 2015; Eden et al 2017), and rato the collection of molecular clouds that fall into their gravitational potential (e.g. Foyle et al 2010), or if the molecular gas forms within the spiral arms themselves. The survey data and a first look at the connection between the molecular gas and large scale structural features of the. 0.75 that have been taken with APEX for this survey between a The latitude range was extended to −1◦ < b < 1◦ towards the Central Molecular Zone, to b < −0.75◦ towards the Nessie filament at l ∼ 338◦, and to b < +0.75◦towards the RCW 120 region at l ∼ 348◦. b Per 0.25 km s−1 channel. c http://www.apex-telescope.org/telescope/efficiency/index.php
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