Search Publications
The Composition of Interstellar Grains toward ζ Ophiuchi: Constraining the Elemental Budget near the Diffuse-dense Cloud Transition
Draine, Bruce T.; Poteet, Charles A.; Whittet, Douglas C. B.
We investigate the composition of interstellar grains along the line of sight toward ζ Ophiuchi, a well-studied environment near the diffuse-dense cloud transition. A spectral decomposition analysis of the solid-state absorbers is performed using archival spectroscopic observations from the Spitzer Space Telescope and Infrared Space Observatory. W…
On the Viability of the PAH Model as an Explanation of the Unidentified Infrared Emission Features
Zhang, Yong; Kwok, Sun
Polycyclic aromatic hydrocarbon (PAH) molecules are widely considered the preferred candidate for the carrier of the unidentified infrared emission bands observed in the interstellar medium and circumstellar envelopes. In this paper, we report the results of fitting a variety of non-PAH spectra (silicates, hydrogenated amorphous carbon, coal, and …
On the Origin of the 11.3 Micron Unidentified Infrared Emission Feature
Zhang, Yong; Kwok, Sun; Sadjadi, SeyedAbdolreza
The 11.3 µm emission feature is a prominent member of the family of unidentified infrared emission (UIE) bands and is frequently attributed to out-of-plane bending modes of polycyclic aromatic hydrocarbon (PAH) molecules. We have performed quantum mechanical calculations of 60 neutral PAH molecules and found that it is difficult to reconcile…
Variability of Disk Emission in Pre-main Sequence and Related Stars. III. Exploring Structural Changes in the Pre-transitional Disk in HD 169142
Inoue, Akio K.; Brown, Alexander; Russell, Ray W. +17 more
We present near-IR (NIR) and far-UV observations of the pre-transitional (gapped) disk in HD 169142 using NASA's Infrared Telescope Facility and Hubble Space Telescope. The combination of our data along with existing data sets into the broadband spectral energy distribution reveals variability of up to 45% between ~1.5-10 µm over a maximum t…
A Theoretical Study on the Vibrational Spectra of Polycyclic Aromatic Hydrocarbon Molecules with Aliphatic Sidegroups
Zhang, Yong; Kwok, Sun; Sadjadi, SeyedAbdolreza
The role of aliphatic side groups in the formation of astronomical unidentified infrared emission (UIE) features is investigated by applying the density functional theory to a series of molecules with mixed aliphatic-aromatic structures. The effects of introducing various aliphatic groups to a fixed polycyclic aromatic hydrocarbon (PAH) core (oval…
Computational Modeling of the Class I Low-Mass Protostar Elias 29 Applying Optical Constants of Ices Processed By High Energy Cosmic Ray Analogs
Rocha, W. R. M.; Pilling, S.
We present a study of the effects of high energy cosmic rays (CRs) over the astrophysical ices, observed toward the embedded class I protostar Elias 29, by using computational modeling and laboratory data. Its spectrum was observed with the Infrared Space Observatory (ISO) covering 2.3-190 µm. The modeling employed the three-dimensional Mont…
Near-infrared Extinction due to Cool Supernova Dust in Cassiopeia A
Koo, Bon-Chul; Lee, Jae-Joon; Moon, Dae-Sik +1 more
We present the results of extinction measurements toward the main ejecta shell of the Cassiopeia A supernova (SN) remnant using the flux ratios between the two near-infrared (NIR) [Fe ii] lines at 1.26 and 1.64 µm. We find a clear correlation between the NIR extinction (E(J-H)) and the radial velocity of ejecta knots, showing that redshifted…
NGC 1266: Characterization of the Nuclear Molecular Gas in an Unusual SB0 Galaxy
Glenn, J.; Maloney, P. R.; Rangwala, N. +1 more
With a substantial nuclear molecular gas reservoir and broad, high-velocity CO molecular line wings previously interpreted as an outflow, NGC 1266 is a rare SB0 galaxy. Previous analyses of interferometry, spectrally resolved low-J CO emission lines, and unresolved high-J emission lines have established basic properties of the molecular gas and th…
A Tale of Three Mysterious Spectral Features in Carbon-rich Evolved Stars: The 21 µm, 30 µm, and “Unidentified Infrared” Emission Features
Li, Aigen; Jiang, B. W.; Mishra, Ajay
The mysterious “21 µm” emission feature seen almost exclusively in the short-lived protoplanetary nebula (PPN) phase of stellar evolution remains unidentified since its discovery two decades ago. This feature is always accompanied by the equally mysterious, unidentified “30 µm” feature and the so-called “unidentified infrared” (UIR) fe…
Infrared Spectral Properties of M Giants
Sloan, G. C.; Goes, C.; Ramirez, R. M. +2 more
We observed a sample of 20 M giants with the Infrared Spectrograph on the Spitzer Space Telescope. Most show absorption structure at 6.6-6.8 µm which we identify as water vapor, and in some cases, the absorption extends from 6.4 µm into the SiO band at 7.5 µm. Variable stars show stronger H2O absorption. While the stre…