Chemical complexity of phosphorous bearing species in various regions of the Interstellar medium

Abstract

Phosphorus related species are not known to be as omnipresent in space as hydrogen, carbon, nitrogen, oxygen, and sulfur-bearing species. Astronomers spotted very few P-bearing molecules in the interstellar medium and circumstellar envelopes. Limited discovery of the P-bearing species imposes severe constraints in modeling the P-chemistry. In this paper, we carry out extensive chemical models to follow the fate of P-bearing species in diffuse clouds, photon-dominated or photodissociation regions (PDRs), and hot cores/corinos. We notice a curious correlation between the abundances of PO and PN and atomic nitrogen. Since N atoms are comparatively abundant in diffuse clouds and PDRs than in the hot core/corino region, PO/PN reflects < 1 in diffuse clouds, << 1 in PDRs, and > 1 in the late warm-up evolutionary phase of the hot core/corino regions. During the end of the post-warm-up phase, we obtain PO/PN > 1 for hot core and < 1 for its low mass analog. We employ a radiative transfer model to investigate the transitions of some of the P-bearing species in diffuse cloud and hot core regions and estimate the line profiles. Our study estimates the required integration time to observe these transitions with ground-based and space-based telescopes. We also carry out quantum chemical computation of the infrared features of PH 3 along with various impurities. We notice that SO 2 overlaps with the PH 3 bendingscissoring modes around ∼ (1000 − 1100) cm −1 . We also find that the presence of CO 2 can strongly influence the intensity of the stretching modes around ∼ 2400 cm −1 of PH 3 .

Quantifying the chemical desorption of H$_2$S and PH$_3$ from amorphous water ice surfaces

“…However, theoretically calculated binding energies for HS, PH 3 , or PH 2 on water ice are available: 2700 K for HS (Wakelam et al 2017), 2200 K for PH 3 , and 1800 K for PH 2 (mean values; Molpeceres & Kästner 2021). Sil et al (2021) and Nguyen et al (2021) also calculated the binding energy of PH 3 on water ice and reported a value similar to that of Molpeceres & Kästner (2021). In our model, we neglect thermal desorption and thermal hopping of H 2 S, HS, PH 3 , and PH 2 .…”

“…Like the gas-phase formation of H 2 S, the formation of PH 3 via gas-phase reactions is inefficient (Thorne et al 1984). Thus, the main formation pathway for gas-phase PH 3 is the formation of PH 3 ice by the sequential hydrogenation of atomic P on grain surfaces, followed by thermal or nonthermal desorption, as assumed in previous astrochemical models (e.g., Charnley & Millar 1994;Aota & Aikawa 2012;Chantzos et al 2020;Sil et al 2021).…”

Radiative transfer modeling of the observed line profiles in G31.41+0.31

“…Detailed chemical modeling has been carried out to study the abundances of the species observed in G31. Our Chemical Model for Molecular Cloud (CMMC) (Das et al, 2015a(Das et al, ,b, 2016Gorai et al, 2017a,b;Sil et al, 2018;Gorai et al, 2020;Sil et al, 2021;Das et al, 2021) is considered for this modeling. 2013) and infall velocity variation is derived from the Equation 1 by using v 1000 = 4.9 km s −1 .…”

“…The time evolution of the physical parameters (H 2 density and temperature) are considered in three significant steps: isothermal collapsing phase, warm-up phase, and post-warmup phase. This type of straightforward model is best suited to study the chemical evolution of hot cores (Gorai et al, 2020;Sil et al, 2021). As discussed in Section 2.2, the gas cloud envelope is divided into 23 spherical shells.…”