Discovery of two infrared objects with strong ice absorption in the AKARI slit-less spectroscopic survey of the Galactic Plane

Abstract

We discover two infrared objects that show deep absorption features of H2O, CO2, and CO ices in the AKARI/Infrared Camera (IRC) slit-less spectroscopic survey of the Galactic plane in 2.5--13 micron. Both objects are located neither in known star-forming regions nor in known dense clouds. For one of the objects, Object 1, we successfully extract a spectrum from 2.5 to 13 micron, which also shows several absorption features in 5--13 micron, including deep silicate absorption at 10 micron. For the other object, Object 2, only a spectrum from 3.1 to 5 micron is reliably extracted due to the presence of nearby overlapping objects and faint nebulosity. Both objects show warm (>100 K) CO gas absorption in addition to the ice absorption features, suggesting that they are embedded young stellar objects (YSOs). On the other hand, both objects have spectral energy distributions (SEDs) that peak at around 5 micron and decrease towards longer wavelengths. These characteristics of the SEDs and the presence of deep absorption features cannot easily be accounted for by standard YSO models. They may be explained as background stars behind dense clouds. We discuss possible nature of the objects and implications of the present discovery.

arXiv comment23 pages, 12 figures, 3 tables

References in corpus (60)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Interstellar Dust Grains
• GLIMPSE: I. A SIRTF Legacy Project to Map the Inner Galaxy
• Toward Understanding Massive Star Formation
• Observations of the Icy Universe
• An Infrared Spectroscopic Sequence of M, L and T Dwarfs
• The AKARI/IRC Mid-Infrared All-Sky Survey
• A Major Asymmetric Dust Trap in a Transition Disk
• The Spitzer ice legacy: Ice evolution from cores to protostars
• Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
• The Infrared Camera (IRC) for AKARI - Design and Imaging Performance
• The c2d Spitzer Spectroscopic Survey of Ices Around Low-Mass Young Stellar Objects: I. H2O and the 5-8 um Bands
• The global dust SED: Tracing the nature and evolution of dust with DustEM
• The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds
• The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects II: CO2
• Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for Inner Milky Way: +68°> l > -70°
• A 3-5 micron VLT spectroscopic survey of embedded young low mass stars I: Structure of the CO ice
• Massive runaways and walkaway stars
• The Origin of Massive O-type Field Stars. Part II: Field O stars as runaways
• Intrinsically Red Sources observed by Spitzer in the Galactic Mid-Plane
• Spitzer Infrared Spectrograph Observations of M, L, and T Dwarfs
• A Classification Scheme for Young Stellar Objects Using the WIDE-FIELD INFRARED SURVEY EXPLORER AllWISE Catalog: Revealing Low-Density Star Formation in the Outer Galaxy
• High and Intermediate-Mass Young Stellar Objects in the Large Magellanic Cloud
• Ice and Dust in the Quiescent Medium of Isolated Dense Cores
• A quantitative analysis of OCN- formation in interstellar ice analogs
• Spitzer Mid-infrared Spectroscopy of Ices Toward Extincted Background Stars
• AKARI IRC infrared 2.5-5 micron spectroscopy of a large sample of luminous infrared galaxies
• Characterizing the nature of embedded young stellar objects through silicate, ice and millimeter observations
• Spitzer Space Telescope Spectroscopy of Ices toward Low Mass Embedded Protostars
• A 3-5$\mu$m VLT spectroscopic survey of embedded young low mass stars II; OCN${}^{-}$
• Near-infrared and Mid-infrared Spectroscopy with the Infrared Camera (IRC) for AKARI
• A modular set of synthetic spectral energy distributions for young stellar objects
• Spitzer Observations of CO2 Ice Towards Field Stars in the Taurus Molecular Cloud
• A Spitzer View of Star Formation in the Cygnus X North Complex
• The Evolution of Massive YSOs in the LMC: Part I. Identification and Spectral Classification
• AKARI Observations of Brown Dwarfs I.: CO and CO_2 Bands in the Near-Infrared Spectra
• Spectroscopic observations of ices around embedded young stellar objects in the Large Magellanic Cloud with AKARI
• Ices in the Quiescent IC 5146 Dense Cloud
• The Asymmetric Thermal Emission of Protoplanetary Disk Surrounding HD 142527 Seen by Subaru/COMICS
• Sulfur Ice Astrochemistry: A Review of Laboratory Studies
• Detection of strongly processed ice in the central starburst of NGC4945
• AKARI Near Infrared Spectroscopy: Detection of H2O and CO2 Ices toward Young Stellar Objects in the Large Magellanic Cloud
• A survey of H${}_2$O, CO${}_2$ and CO ice features towards background stars and low mass YSOs using AKARI
• VLT-ISAAC 3-5 micron spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in Vela
• ESO-VLT and Spitzer spectroscopy of IRAS05328-6827: a massive young stellar object in the Large Magellanic Cloud
• AKARI Infrared Camera Survey of the Large Magellanic Cloud. I. Point Source Catalog
• Carbon Monoxide bands in M dwarfs
• Extreme Infrared Variables from UKIDSS - I. A Concentration in Star Forming Regions
• Properties of protostars in the Elephant Trunk globule IC 1396A
• VLT/ISAAC infrared spectroscopy of embedded high-mass YSOs in the Large Magellanic Cloud: Methanol and the 3.47 micron band
• First Spectroscopic Identification of Massive Young Stellar Objects in the Galactic Center
• Absorption at 11 microns in the interstellar medium and embedded sources: evidence for crystalline silicates
• Two dimensional ice mapping of molecular cores
• Chemical modelling of dust-gas chemistry within AGB outflows III. Photoprocessing of the ice and return to the ISM
• Abundant Methanol Ice toward a Massive Young Stellar Object in the Central Molecular Zone
• Revised Wavelength and Spectral Response Calibrations for AKARI Near-Infrared Grism Spectroscopy: Cryogenic Phase
• Difference in the spatial distribution between H_2O and CO_2 ices in M82 found with AKARI
• Source clustering in the Hi-GAL survey determined using a minimum spanning tree method
• Discovery of a Long-Lived, High Amplitude Dusty Infrared Transient
• AKARI near-infrared spectroscopy of the extended green object G318.05+0.09: Detection of CO fundamental ro-vibrational emission

Cited by in corpus (4)

• LIDA - The Leiden Ice Database for Astrochemistry
• Near-infrared spectroscopy of a massive young stellar object in the direction toward the Galactic Center: XCN and aromatic C-D features
• Ice features of low-luminosity protostars in near-infrared spectra of AKARI/IRC
• The SPHEREx Target List of Ice Sources (SPLICES)