Planckearly results. XXIV. Dust in the diffuse interstellar medium and the Galactic halo

Abstract

This paper presents the first results from a comparison of Planck dust maps at 353, 545 and 857 GHz, along with IRAS data at 3000 (100 μm) and 5000 GHz (60 μm), with Green Bank Telescope 21-cm observations of H i in 14 fields covering more than 800 deg 2 at high Galactic latitude. The main goal of this study is to estimate the far-infrared to sub-millimeter (submm) emissivity of dust in the diffuse local interstellar medium (ISM) and in the intermediate-velocity (IVC) and high-velocity clouds (HVC) of the Galactic halo. Galactic dust emission for fields with average H i column density lower than 2 × 10 20 cm −2 is well correlated with 21-cm emission because in such diffuse areas the hydrogen is predominantly in the neutral atomic phase. The residual emission in these fields, once the H i-correlated emission is removed, is consistent with the expected statistical properties of the cosmic infrared background fluctuations. The brighter fields in our sample, with an average H i column density greater than 2 × 10 20 cm −2 , show significant excess dust emission compared to the H i column density. Regions of excess lie in organized structures that suggest the presence of hydrogen in molecular form, though they are not always correlated with CO emission. In the higher H i column density fields the excess emission at 857 GHz is about 40% of that coming from the H i, but over all the high latitude fields surveyed the molecular mass faction is about 10%. Dust emission from IVCs is detected with high significance by this correlation analysis. Its spectral properties are consistent with, compared to the local ISM values, significantly hotter dust (T ∼ 20 K), lower submm dust opacity normalized per H-atom, and a relative abundance of very small grains to large grains about four times higher. These results are compatible with expectations for clouds that are part of the Galactic fountain in which there is dust shattering and fragmentation. Correlated dust emission in HVCs is not detected; the average of the 99.9% confidence upper limits to the emissivity is 0.15 times the local ISM value at 857 and 3000 GHz, in accordance with gas phase evidence for lower metallicity and depletion in these clouds. Unexpected anti-correlated variations of the dust temperature and emission cross-section per H atom are identified in the local ISM and IVCs, a trend that continues into molecular environments. This suggests that dust growth through aggregation, seen in molecular clouds, is active much earlier in the cloud condensation and star formation processes.

Entanglement rates and haulout abundance trends of Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lions on the north coast of Washington state

“…Many marine organisms are affected by marine debris and other manmade materials through entanglement. Instances of entanglement have been recorded for at least 32 species of marine mammals globally [4], and for some, like the northern fur seal (Callorhinus ursinus) and the endangered Hawaiian monk seal (Monachus schauinslandi), entanglement was thought to have contributed to population declines [6][7][8]. For pinnipeds specifically, entanglement has been documented for more than half of the existing species [2,4,9].…”

Substructure, supernovae, and time resolved star formation history for Upper Scorpius

“…From the 308 sources in our ρ Oph substructure, only 17 are not contained in the previous census from Cánovas et al (2019) nor . We remark again that ρ Oph is composed by several smaller populations with ages between 0 (Pillitteri et al 2016) and 6 (Esplin & Luhman 2020)] Myr in a complex structure of stars and molecular clouds. We will revisit these properties in our proposed star formation scenario for USco in section 6.…”

“…Hence, observations of nearby OB associations are fundamental for the test and proposal of models ranging from the early stages of stellar evolution to the structure, composition and dynamics of the Galactic populations. In this context, Upper Scorpius (USco) has a great importance as it is thought to be the youngest group of the three conforming the Scorpius-Centaurus OB2 association (Sco-Cen), the nearest to Earth (e.g., de Geus 1992;de Zeeuw et al 1997;Pecaut & Mamajek 2016) and one of the nearest places (∼140 pc) that show evidence of active or recent star formation (Pillitteri et al 2016;de Zeeuw et al 1997;Preibisch & Mamajek 2008). Therefore, in depth efforts have been made in order to provide a systematic characterization of the stellar populations in USco.…”