Duncan Farrah — Page 8

arXiv2003

The K-band Hubble diagram of sub-mm galaxies and hyperluminous galaxies

We present the K-band Hubble diagrams (K-z relations) of sub-mm-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K-z relation of HLIRGs, indistinguishable from that of the most luminous radiogalaxies. Like radiogalaxies, the HLIRG K-z relation at z<~3 is consistent with a passively evolving ~3L* instantaneous starburst starting from a redshift of z~10. In contrast, many sub-mm selected galaxies are >~2 magnitudes fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than sub-mm-selected galaxies due to the 60 micron selection of some, so the location on the K-z relation may be related to the presence of the most massive AGN. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.

astro-ph↗

arXiv2002

The dusty type IIn Supernova 1998S

The type IIn SN 1998S is one of the most remarkable core-collapse supernovae ever observed. It underwent a complex interaction with a substantial circumstellar medium, resulting in radiation at wavelengths from radio to X-rays. IR and optical observations have revealed a wide variety of broad and narrow emission lines. Examination of the SN/CSM interaction and of the ejecta spectra has allowed us to deduce that the supernova probably arose from a massive, RSG progenitor having a large (>3200 AU radius), dusty circumstellar disk. SN 1998S also developed one of the strongest, most persistent infrared excesses ever seen in a supernova. IR/optical monitoring of SN 1998S has been carried out to nearly 1200 days post-explosion. This includes coverage to wavelengths as long as 4.7 microns, making SN 1998S only the second supernova (after SN 1987A) to be observed in this spectral region. Fading of the central and redshifted components of the late-time H I and He I line profiles suggests strongly that dust condensed in the ejecta. However, it is less clear whether the strong late-time IR emission arose from this dust, or from an IR echo in the dusty CSM. One interesting possibility is that dust condensed in the cool dense shell between the outer and reverse shocks, thus simultaneously producing both the line obscuration and the IR emission.

astro-ph↗