arXiv subjects

Igor Petrashkevich

Publications and source records attributed to Igor Petrashkevich.

4 recordsLinked to original sources

arXiv2026

Mapping Interstellar Ice Inventory toward Class 0 Protostars in Star-forming Region Orion A with JWST Data

We present a detailed study of the spatial distribution and chemical composition of interstellar ices toward six Class 0 protostars (HOPS-56, HOPS-60, HOPS-73, HOPS-91, HOPS-96, and HOPS-108) in the Orion A molecular cloud. Using high-resolution spectroscopic data from the JWST NIRspec and MIRI MRS instruments (4.3 - 8.1 $\mu$m), we have constructed the first pixel by pixel absorption maps with a resolution of $\sim$100~AU for key ice species, including $^{13}$CO$_2$, OCN$^-$, CO, H$_2$O, NH$_4^+$, and H$_2$CO. CH$_4$ and OCS were analyzed toward the continuum peaks. The column densities were derived by fitting the observed spectra with laboratory ice analogs. We employed radiative transfer modeling, which confirmed the reliability of our column density estimates within the protostellar envelopes. Our analysis reveals significant variations in ice abundances and distributions, reflecting the physical structure and energetic processes within the envelopes. Specifically, we observe the influence of protostellar heating and outflows on the ice mantles, most notably in HOPS-60. The total ice composition is consistent with astrochemical models and covers $\sim$90% of observed ice inventory suggesting that ice is primarily formed during the prestellar stage and subsequently inherited by the protostellar envelope. Based on the abundance relative to water, the sources can be categorized into two distinct groups, possibly indicating evolutionary differences or variations in envelope density and temperature profiles.

astro-ph.GA↗

arXiv2026

Infrared spectra of methane-containing ice mixtures for JWST data analyses

Context. Solid methane (CH$_4$) is an important molecule in interstellar and planetary environments, serving as a precursor to complex organic compounds, and it is a potential biosignature in exoplanetary studies. Despite its significance, laboratory data on the low temperature phase of methane below 10 K remain limited. Aims. We obtained spectra of methane in binary mixtures at 10 K and compared them to the spectra obtained at 6.7 K. These temperatures correspond to phases II and II* of pure methane and are representative of dark molecular clouds and protostars in early stages. We also tested whether the data we obtained can be applied to interpret JWST data. Methods. Laboratory reference spectra were obtained with the ISEAge setup via Fourier transform infrared spectroscopy in transmission mode. A weighted $\chi^2$ minimization was used for the fitting. Results. We present infrared spectra with corresponding band strengths of pure methane and binary mixtures with methane: CH$_4$:H$_2$O, CH$_4$:CO$_2$, CH$_4$:CH$_3$OH, and CH$_4$:NH$_3$ at 6.7 K and 10 K. They show an increase of 20% in mixtures compared to the commonly used 10 K band strength value of pure methane. We also tested whether the spectra can be used on open JWST data by probing the spatial distribution of methane in B335. We also present additional experiments concerning the phase transition of methane between phase II* and phase II. Conclusions. Our results reveal distinct spectral features for methane in non-H$_2$O environments that enable a more accurate interpretation of JWST observations. The dataset of spectra is publicly available on Zenodo and can be used for fitting JWST data.

astro-ph.SR↗

arXiv2025

Deuterium fractionation and CO depletion in Barnard 5

Deuterium fractionation provides a key diagnostic of the physical and chemical evolution of prestellar and protostellar cores, where it is strongly linked to CO depletion in cold, dense gas. We present the first spatially resolved maps of deuterium fraction and CO depletion in the Barnard 5 (B5) region of the Perseus molecular cloud, covering both a starless core and the protostellar core hosting the Class 0/I source IRAS 03445+3242. Using IRAM 30~m observations of N$_2$H$^+$(1--0), N$_2$D$^+$(1--0), H$^{13}$CO$^+$(1--0), and DCO$^+$(2--1), complemented by C$^{18}$O(2--1) data, we derive column density, deuterium fraction, and CO depletion maps. We find that the deuterium fraction in both mentioned nitrogen- and carbon-bearing species increases from the protostellar to the starless core, reaching $R_D^{\rm N_2H^+}=0.43\pm0.10$ and $R_D^{\rm HCO^+}=0.09\pm0.02$ in the starless core, compared with $0.15\pm0.03$ and $0.05\pm0.01$, respectively, in the protostellar core. The CO depletion factor also rises from $4.1\pm0.1$ to $5.0\pm0.1$ across the same transition. While the embedded YSO reduces deuteration in the dense inner gas, the less dense envelope traced by HCO$^+$ is only slightly affected at our resolution. Our analysis confirms that CO freeze-out and the presence of a protostar jointly regulate deuterium chemistry in star-forming regions.

astro-ph.GA↗

arXiv2024

Solid and Gaseous Methane in IRAS 23385+6053 as seen with Open JWST Data

We present a new description of the 7.7~$\mu$m region towards the high-mass star-forming region IRAS 23385+6053 taken from open James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer (JWST MIRI/MRS) data. This area is commonly attributed to the $\nu_4$ deformation mode of methane ice. For the first time gaseous and solid methane were analyzed simultaneously in IRAS 23385+6053. The band at 7.58--7.8 $\mu$m (1320--1280 cm$^{-1}$) is interpreted as a wide solid absorption methane feature overlapped by the sharp features of the methane emission. We report the detection of gaseous methane and estimate its emitting area radius~$R$, temperature~$T$ and column density~$N$ as $R=2940$~au, $T=103^{+13}_{-11}$~K, and $N=0.78_{+6.18}^{-0.64}\times10^{17}$~cm$^{-2}$, correspondingly. The ice content was analyzed with the laboratory spectra dataset of methane in different molecular environments obtained on the Ice Spectroscopy Experimental Aggregate (ISEAge). We were able to describe the wide feature of solid methane with the following laboratory spectra: CH$_4$~:~CO$_2$~=~1~:~5 (at $27.4^{+6.0}_{-10.8}$~K) and CH$_4$~:~H$_2$O~=~1~:~10 (at $8.4^{+16.4}_{-1.7}$~K) deposited at 6.7~K and warmed up at a rate of 0.5 K per minute. The derived column densities are $N_{\text{CH}_4}$(CO$_2$)~=~$2.97^{+0.37}_{-0.57}\times10^{17}$~cm$^{-2}$ and $N_{\text{CH}_4}$(H$_2$O)~=~$1.02^{+0.46}_{-0.27}\times10^{17}$~cm$^{-2}$. According to the best fit solid methane is mostly surrounded by CO$_2$ rather than H$_2$O. The residuals analysis reveals the unassigned region at 1283--1297~cm$^{-1}$ (7.71--7.79~$\mu$m) which is tentatively assigned to nitrous oxide (N$_2$O) in various environments.

astro-ph.GA↗