Yong-Hyun Lee

UWISH2 -- The UKIRT Widefield Infrared Survey for H2

The definitive version can be found at : http://onlinelibrary.wiley.com/ Copyright Wiley-Blackwell

Phosphorus in the young supernova remnant Cassiopeia A.

We Are Stardust Most of the universes chemical elements were produced in stars, with the heaviest elements being produced when stars explode. Barlow et al. (p. 1343) used the Herschel Space Observatory to obtain submillimeter spectra of the Crab Nebula, the remains of a stellar explosion that was witnessed on Earth in 1054 AD, and detected the first evidence of a noble gas-containing molecular ion in space—36ArH+. Koo et al. (p. 1346) obtained near-infrared spectroscopic observations of the remains of another stellar explosion, Cassiopeia A, with the Palomar 5-m Hale telescope, and found evidence that a substantial amount of phosphorus was formed in the explosion. Among the six elements essential for life (hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur), only the origin of phosphorus remained to be confirmed by observation. Spectroscopic observations of the remains of stellar explosions confirm that argon-36 and phosphorus are produced in such energetic events. Phosphorus (31P), which is essential for life, is thought to be synthesized in massive stars and dispersed into interstellar space when these stars explode as supernovae (SNe). Here, we report on near-infrared spectroscopic observations of the young SN remnant Cassiopeia A, which show that the abundance ratio of phosphorus to the major nucleosynthetic product iron (56Fe) in SN material is up to 100 times the average ratio of the Milky Way, confirming that phosphorus is produced in SNe. The observed range is compatible with predictions from SN nucleosynthetic models but not with the scenario in which the chemical elements in the inner SN layers are completely mixed by hydrodynamic instabilities during the explosion.

NEAR-INFRARED EXTINCTION DUE TO COOL SUPERNOVA DUST IN CASSIOPEIA A

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 () and the radial velocity of ejecta knots, showing that redshifted knots are systematically more obscured than blueshifted ones. This internal “self-extinction” strongly indicates that a large amount of SN dust resides inside and around the main ejecta shell. At one location in the southern part of the shell, we measure by the SN dust of 0.23 ± 0.05 mag. By analyzing the spectral energy distribution of thermal dust emission at that location, we show that there are warm (∼100 K) and cool (∼40 K) SN dust components and that the latter is responsible for the observed . We investigate the possible grain species and size of each component and find that the warm SN dust needs to be silicate grains such as MgSiO3, Mg2SiO4, and SiO2, whereas the cool dust could be either small (≲0.01 μm) Fe or large (≳0.1 μm) Si grains. We suggest that the warm and cool dust components in Cassiopeia A represent grain species produced in diffuse SN ejecta and in dense ejecta clumps, respectively.

UKIRT Widefield Infrared Survey for Fe

The United Kingdom Infrared Telescope (UKIRT)Widefield Infrared Survey for Fe+ (UWIFE) is a 180 deg2 imaging survey of the first Galactic quadrant (7° < l < 62° |b| <1°.5) that uses a narrow-band filter centred on the [Fe II] 1.644-I¼m emission line. The [Fe II] 1.644-I¼m emission is a good tracer of dense, shock-excited gas, and the survey will probe violent environments around stars: star-forming regions, evolved stars, and supernova remnants, among others. The UWIFE survey is designed to complement the existing UKIRTW idefield Infrared Survey for H2 (UWISH2). The survey will also complement existing broad-band surveys. The observed images have a nominal 5I? detection limit of 18.7 mag for point sources, with a median seeing of 0.83 arcsec. For extended sources, we estimate a surface brightness limit of 8.1 A? 10-20 W m-2 arcsec-2. In this paper, we present an overview and some preliminary results of this survey. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

NEAR-INFRARED SPECTROSCOPY OF YOUNG GALACTIC SUPERNOVA REMNANTS

Young Galactic supernova remnants (SNRs) are where we can observe closely supernova (SN) ejecta and their interaction with the circumstellar/interstellar medium. They also provide an opportunity to explore the explosion and the nal stage of the evolution of massive stars. Near-infrared (NIR) emission lines in SNRs mostly originate from shocked dense material. In shocked SN ejecta, forbidden lines from heavy ions are prominent, while in shocked circumstellar/interstellar medium, [Fe II] and H₂ lines are prominent. [Fe II] lines are strong in both media, and therefore [Fe II] line images provide a good starting point for the NIR study of SNRs. There are about twenty SNRs detected in [Fe II] lines, some of which have been studied in NIR spectroscopy. We will review the NIR [Fe II] observations of SNRs and introduce our recent NIR spectroscopic study of the young core-collapse SNR Cas A where we detected strong [P II] lines.

High-resolution Near-IR Spectral Mapping with H2 and [Fe ii] Lines of Multiple Outflows around LkHα 234

US National Science Foundation [AST-1229522]; University of Texas at Austin; Korean GMT Project of KASI; National Research Foundation of Korea (NRF) - Korean government (MSIP) [2012R1A4A1028713]

Supernova Remnants in the UWISH2 and UWIFE Surveys

We report the preliminary results for the detection of H2 and [Fe II] line features around the Galactic supernova remnants (SNRs) from the UWISH2 and UWIFE surveys that cover the first galactic quadrant of 7◦ < l < 65◦ and |b| < 1.3◦. By this time, we have found a total of 17 H2 -emitting and 14 [Fe II]-emitting SNRs in the coverage, and more than a half of them are detected in both H2 and [Fe II] emissions, which implies that the environment of these SNRs might be complex and composed of multi-phase medium. In this paper, we present our identification strategy and some preliminary results including H2 and [Fe II] luminosity distributions.