Astrochemistry

The SPHEREx Target List of Ice Sources (SPLICES)

By Keith Cowing

Status Report

astro-ph.GA

January 31, 2025

Filed under astro-ph.GA, astrochemistry, astronomy, Cygnus X-2, ice, imaging, Interstellar, Magellanic Cloud, Milky Way, molecular clouds, spacetroscopy, SPHEREx, Water

The SPHEREx Target List of Ice Sources (SPLICES) — Regions surveyed to identify sources likely to present spectra with detectable ice features of H₂O, CO, CO₂, ¹³CO₂, and other species in the 3 − 5 µm wavelength range where SPHEREx is sensitive. Upper panel: The regions are projected onto a background greyscale image representing the Rowles & Froebrich (2009) extinction map stretched from AV = 0 (white) to 2 mag (black). Solid red lines enclose the fields from which candidate SPHEREx targets have been drawn. Dotted blue lines indicate the boundaries of nearby molecular clouds as defined by Zucker et al. (2019). Red circles indicate the locations and sizes of ‘dark nebulae’ identified on the Palomar plates by Lynds (1962). Lower panel: same symbols as the upper panel, but the background greyscale image is the integrated ¹²CO(1-0) line intensity survey executed with the CfA 1.2 m telescope and its southern hemisphere counterpart (e.g., Dame et al. 2001; Heyer & Dame 2015). The inverted greyscale stretch ranges from −1 to 25 K km s⁻¹, to indicate the extensive CO survey footprint. The white background indicates regions unobserved by the CfA CO survey except for the Magellanic Clouds (the SMC and LMC maps are described respectively in Rubio et al. (1991) and Cohen et al. (1988)). — astro-ph.GA

One of the primary objectives of the SPHEREx mission is to understand the origin of molecules such as H₂O, CO₂, and other volatile compounds at the early stages of planetary system formation.

Because the vast majority of these compounds — typically exceeding 95% — exist in the solid phase rather than the gaseous phase in the systems of concern here, the observing strategy planned to characterize them is slightly unusual. Specifically, SPHEREx will target highly obscured sources throughout the Milky Way, and observe the species of concern in absorption against background illumination.

SPHEREx spectrophotometry will yield ice column density measurements for millions of obscured Milky Way sources of all ages and types. By correlating those column densities with source ages, the SPHEREx mission will shed light on whether those molecules were formed in situ along with their nascent stellar systems, or whether instead they formed elsewhereand were introduced into those systems after their formation.

To that end, this work describes version 7.1 of the SPHEREx Target List of Ice Sources (SPLICES) for the community. It contains about 8.6 million objects brighter than W2~12 Vega mag over much of the sky, principally within a broad strip running the length of the Milky Way midplane, but also within high-latitude molecular clouds and even the Magellanic Clouds.

An illustration of the density and distribution of SPHEREx Ices targets, showing the Cygnus region as imaged by the Cygnus-X program (Beerer et al. 2010). Coordinates are in degrees of Galactic longitude and latitude. Upper panel: The WISE 3.4 µm Cygnus X mosaic showing the nebulosity tracing regions of high density in the Milky Way interstellar medium. Lower panel: The same, but overlaid with approximately 24500 green dots indicating the positions of SPLICES targets having H − W2 > 1.55, i.e., the targets thought to lie behind AV > 10 mag of extinction. Also shown (in red) are the positions of another 600 H-undetected targets satisfying the Ks − W2 color criterion; these are candidate deeply embedded objects. The SPLICES targets in this field tend to lie in regions of high nebulosity, although some sources evidently lie distant from the nebulosity. — astro-ph.GA

Matthew L. N. Ashby (1), Joseph L. Hora (1), Kiran Lakshmipathaiah (2), Sarita Vig (2), Rama Krishna Sai Subrahmanyam Gorthi (3), Miju Kang (4), Volker Tolls (1), Gary J. Melnick (1), Michael W. Werner (5), Brendan P. Crill (5), Daniel C. Masters (6), Carlos Contreras Pena (7), Jeong-Eun Lee (7), Jaeyeong Kim (4), Ho-Gyu Lee (4), Sung-Yong Yoon (8 and 4), Soung-Chul Yang (4), Nicholas Flagey (9), Bertrand Mennesson (10) ((1) Center for Astrophysics | Harvard & Smithsonian, (2) Indian Institute of Space science and Technology, (3) Department of Electrical Engineering, Indian Institute of Tirupati, India (4) Korea Astronomy and Space Science Institute, Republic of Korea, (5) Jet Propulsion Laboratory, California Institute of Technology, (6) Infrared Processing and Analysis Center, California Institute of Technology, (7) Department of Physics and Astronomy, Seoul National University, Republic of Korea, (8) School of Space Research, Kyung Hee University, Republic of Korea, (9) Space Telescope Science Institute, (10) Jet Propulsion Laboratory)

Comments: Published by ApJ. 21 pages, 6 figures. This article documents the original version of SPLICES (7.1). The current version as well as the complete catalog is publicly available along with release notes documenting all additions and changes at the NASA/IPAC Infrared Science Archive (IRSA) at this URL: https://irsa.ipac.caltech.edu/data/SPHEREx/SPLICES/
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2501.17797 [astro-ph.GA] (or arXiv:2501.17797v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2501.17797
Focus to learn more
Journal reference: ApJ, 949, 105 (2023)
Related DOI:
https://doi.org/10.3847/1538-4357/acc86b
Focus to learn more
Submission history
From: Matthew Ashby
[v1] Wed, 29 Jan 2025 17:35:41 UTC (32,046 KB)
https://arxiv.org/abs/2501.17797
Astrobiology, Astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter