We have analyzed Spitzer IRAC, MIPS and IRS data on the nucleus of M81. The data include spectral... more We have analyzed Spitzer IRAC, MIPS and IRS data on the nucleus of M81. The data include spectral images in both continuum and lines, and confirm the very unusual spectral energy distribution that we hypothesized in our earlier paper on M81 (Willner et al., ApJS, 154, 222, 2004). We model the unusual SED, compare it with the mid-IR SEDs of other LINERS and with a range of types of galactic nuclei including AGN and elliptical nuclei, and discuss the implications. We also model the atomic and molecular lines seen. We will discuss the origins of these features in the context of LINERs, elliptical galaxies, and the nature of the nuclei of AGN.
Proceedings of the International Astronomical Union
The infrared (IR) spectra of many evolved carbon-rich stars exhibit two prominent dust emission f... more The infrared (IR) spectra of many evolved carbon-rich stars exhibit two prominent dust emission features peaking around 21um and 30um, with the former exclusively seen in proto-planetary nebulae (PPNe), while the latter seen in a much wider range of objects, including AGB stars, PPNe and planetary nebulae (PNe). The 30um feature is seen in all the 21um sources, but no correlation is found between these two features. Over a dozen carrier candidates have been proposed for the 21um feature, but none of them has been widely accepted and the nature of the 21um feature remains a mystery. The carrier of the 30um feature also remains unidentied. MgS dust, once widely accepted as a valid carrier, was ruled out because of the sulfur budget problem. In this work we examine nano-sized FeO dust as a carrier for the 21um feature. We calculate the IR emission spectrum of FeO nanodust which undergoes single-photon heating in PPNe. It is found that the 21um feature emitted by FeO nanodust is too bro...
Well-resolved infrared observations of nearby galaxies are of fundamental im- portance to the stu... more Well-resolved infrared observations of nearby galaxies are of fundamental im- portance to the study of the processes that aect galactic evolution. In this Letter, we report on the rst imaging results from the Spitzer Infrared Nearby Galaxies Survey (SINGS) using observations of the Sb galaxy NGC 7331. We present images of NGC 7331 over a large range of wavelengths that
We present near-infrared images of the centers of 27 galaxies from the SINGS (the Spitzer Infrare... more We present near-infrared images of the centers of 27 galaxies from the SINGS (the Spitzer Infrared Nearby Galaxies Survey) sample, obtained with HST/NICMOS in the H-band and Paschen-alpha line emission. The Paschen-alpha images provide nearly--extinction--insensitive maps of the massive star formation rate (SFR) in the dusty cores of the galaxies, while the H-band images trace the stellar mass distribution. We
We have analyzed Spitzer IRAC, MIPS and IRS data on the nucleus of M81. The data include spectral... more We have analyzed Spitzer IRAC, MIPS and IRS data on the nucleus of M81. The data include spectral images in both continuum and lines, and confirm the very unusual spectral energy distribution that we hypothesized in our earlier paper on M81 (Willner et al., ApJS, 154, 222, 2004). We model the unusual SED, compare it with the mid-IR SEDs of other LINERS and with a range of types of galactic nuclei including AGN and elliptical nuclei, and discuss the implications. We also model the atomic and molecular lines seen. We will discuss the origins of these features in the context of LINERs, elliptical galaxies, and the nature of the nuclei of AGN.
Proceedings of the International Astronomical Union
The infrared (IR) spectra of many evolved carbon-rich stars exhibit two prominent dust emission f... more The infrared (IR) spectra of many evolved carbon-rich stars exhibit two prominent dust emission features peaking around 21um and 30um, with the former exclusively seen in proto-planetary nebulae (PPNe), while the latter seen in a much wider range of objects, including AGB stars, PPNe and planetary nebulae (PNe). The 30um feature is seen in all the 21um sources, but no correlation is found between these two features. Over a dozen carrier candidates have been proposed for the 21um feature, but none of them has been widely accepted and the nature of the 21um feature remains a mystery. The carrier of the 30um feature also remains unidentied. MgS dust, once widely accepted as a valid carrier, was ruled out because of the sulfur budget problem. In this work we examine nano-sized FeO dust as a carrier for the 21um feature. We calculate the IR emission spectrum of FeO nanodust which undergoes single-photon heating in PPNe. It is found that the 21um feature emitted by FeO nanodust is too bro...
Well-resolved infrared observations of nearby galaxies are of fundamental im- portance to the stu... more Well-resolved infrared observations of nearby galaxies are of fundamental im- portance to the study of the processes that aect galactic evolution. In this Letter, we report on the rst imaging results from the Spitzer Infrared Nearby Galaxies Survey (SINGS) using observations of the Sb galaxy NGC 7331. We present images of NGC 7331 over a large range of wavelengths that
We present near-infrared images of the centers of 27 galaxies from the SINGS (the Spitzer Infrare... more We present near-infrared images of the centers of 27 galaxies from the SINGS (the Spitzer Infrared Nearby Galaxies Survey) sample, obtained with HST/NICMOS in the H-band and Paschen-alpha line emission. The Paschen-alpha images provide nearly--extinction--insensitive maps of the massive star formation rate (SFR) in the dusty cores of the galaxies, while the H-band images trace the stellar mass distribution. We
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Papers by Aigen Li