Search Publications
A Study of the Photometric and Spectroscopic Variations of the Prototypical FU Orionis-type Star V1057 Cyg
Cseh, B.; Kriskovics, L.; Pál, A. +19 more
Among the low-mass pre-main sequence stars, a small group called FU Orionis-type objects (FUors) are notable for undergoing powerful accretion outbursts. V1057 Cyg, a classical example of an FUor, went into outburst around 1969-1970, after which it faded rapidly, making it the fastest-fading FUor known. Around 1995, a more rapid increase in fading…
M17 MIR: A Massive Protostar with Multiple Accretion Outbursts
Chen, Zhiwei; Chen, Xuepeng; Haas, Martin +3 more
We report the discovery of a massive protostar M17 MIR embedded in a hot molecular core in M17. The multiwavelength data obtained during 1993-2019 show significant mid-IR (MIR) variations, which can be split into three stages: the decreasing phase during 1993.03-mid-2004, the quiescent phase from mid-2004 to mid-2010, and the rebrightening phase f…
Tracing PAH Size in Prominent Nearby Mid-Infrared Environments
Tielens, A. G. G. M.; Peeters, E.; Vacca, W. D. +2 more
We present observations from the First Light Infrared TEst CAMera (FLITECAM) on board the Stratospheric Observatory for Infrared Astronomy, the Spitzer Infrared Array Camera (IRAC), and the Spitzer Infrared Spectrograph SH mode in three well-known photodissociation regions, the reflection nebulae (RNe) NGC 7023 and NGC 2023 and to the southeast of…
The 6.2 µm PAH Feature and the Role of Nitrogen: Revisited
Boersma, C.; Peeters, E.; Ricca, A.
This study revisits the role that nitrogen inclusion in polycyclic aromatic hydrocarbons (PAHs; those with nitrogen inclusion, PANHs) plays in their infrared (IR) spectral properties. We present spectra of pure PAHs, PANHs, and protonated PANHs, computed using density functional theory and basis sets that treat polarization. We investigate trends …
Far-Infrared Line Diagnostics: Improving N/O Abundance Estimates for Dusty Galaxies
Lamarche, C.; Stacey, G. J.; Higdon, J. +8 more
The nitrogen-to-oxygen (N/O) abundance ratio is an important diagnostic of galaxy evolution because the ratio is closely tied to the growth of metallicity and the star formation history in galaxies. Estimates for the N/O are traditionally made with optical lines that could suffer from extinction and excitation effects, so the N/O is arguably measu…
Regulating Star Formation in Nearby Dusty Galaxies: Low Photoelectric Efficiencies in the Most Compact Systems
Inami, H.; Pope, A.; Armus, L. +5 more
Star formation in galaxies is regulated by heating and cooling in the interstellar medium (ISM). In particular, the processing of molecular gas into stars will depend strongly on the ratio of gas heating to gas cooling in the neutral gas around sites of recent star formation. In this work, we combine mid-infrared (mid-IR) observations of polycycli…
On the Collisional Disalignment of Dust Grains in Illuminated and Shaded Regions of IC 63
Soam, Archana; Andersson, B. -G.; Acosta-Pulido, Jose +5 more
Interstellar dust grain alignment causes polarization from UV to mm wavelengths, allowing the study of the geometry and strength of the magnetic field. Over the last couple of decades, observations and theory have led to the establishment of the radiative alignment torque mechanism as a leading candidate to explain the effect. With a quantitativel…
The 3.3 µm Infrared Emission Feature: Observational and Laboratory Constraints on Its Carrier
Tokunaga, Alan T.; Bernstein, Lawrence S.
We examine the self-consistency of laboratory and observational data for potential carriers of the 3.3 µm infrared emission feature (IEF), a member of the ubiquitous family of strong interstellar IEFs at 3.3, 3.4, 6.2, 7.7, 8.6, 11.2, and 12.7 µm. Previous studies have shown that most Galactic sources (reflection nebulae, H II regions,…
Molecular Gas in the Nuclear Region of NGC 6240
Bally, John; Glenn, Jason; Rangwala, Naseem +3 more
NGC 6240 is a luminous infrared galaxy in the local universe in the midst of a major merger. We analyze high-resolution interferometric observations of warm molecular gas using CO J = 3-2 and 6-5 in the central few kpc of NGC 6240 taken by the Atacama Large Millimeter Array. Using these CO line observations, we model the density distribution and k…
Spatial Variation in Temperature and Density in the IC 63 PDR from H2 Spectroscopy
Karoly, Janik; Soam, Archana; Andersson, B. -G. +2 more
We have measured the gas temperature in the IC 63 photodissociation region (PDR) using the S(1) and S(5) pure rotation lines of molecular hydrogen with SOFIA/EXES. We divide the PDR into three regions for analysis based on the illumination from γ Cas: sunny, ridge, and shady. Constructing rotation diagrams for the different regions, we obtain temp…