1st Abstract
| Title (1st Abstract) | Near-Infrared Spectroscopic Study of Supernova Ejecta and Supernova Dust in Cassiopeia A |
| First Author | Yong-Hyun Lee |
| Affiliation | Seoul National University |
| Additional Authors | Bon-Chul Koo / Seoul National University |
| Presentation options | |
| Session | |
| 1st Abstract | We have carried out near-infrared (NIR) spectroscopic observations of the Cassiopeia A supernova (SN) remnant. We obtained medium-resolution, $JHK$ (0.95–2.46 $mu$m) spectra around the main ejecta shell. Using a clump-finding algorithm, we identified 63 `knots’ in the two-dimensional dispersed images, and derived their spectroscopic properties. We first present the result of spectral classification of the knots using Principal Component (PC) Analysis. We found that the NIR spectral characteristics of the knots can be mostly (85%) represented by three PCs composed of different sets of emission lines: (1) recombination lines of H and He together with [N I] lines, (2) forbidden lines of Si, P, and S lines, and (3) forbidden Fe lines. The distribution of the knots in the PC planes matches well with the above spectral groups, and we classified the knots into the three corresponding groups, i.e., He-rich, S-rich, and Fe-rich knots. The kinematic and chemical properties of the former two groups match well with those of Quasi-Stationary Flocculi and Fast-Moving Knots known from optical studies. The Fe-rich knots show intermediate characteristics between the former two groups, and we suggest that they are the SN ejecta material from the innermost layer of the progenitor. We also present the results of extinction measurements using the flux ratios between the two NIR [Fe II] lines at 1.257 and 1.644 $mu$m. We have found a clear correlation between the NIR extinction and the radial velocity of ejecta knots, indicating the presence of a large amount of SN dust inside and around the main ejecta shell. In a southern part of the ejecta shell, by analyzing the NIR extinction together with far-infrared thermal dust emission, we show that there are warm ($sim$100 K) and cool ($sim$40 K) SN dust components and that the former needs to be silicate grains while the latter, which is responsible for the observed NIR extinction, could be either small ($lesssim$0.01 $mu$m) Fe or large ($gtrsim$0.1 $mu$m) Si grains. We suggest that the warm and cool dust components represent grain species produced in diffuse SN ejecta and in dense ejecta clumps, respectively. |
2nd Abstract
| Title (2nd abstract) | Supernova Remnants in the UWIFE and UWISH2 Surveys |
| First Author (2nd abstract) | Yong-Hyun Lee |
| Affiliation (2nd abstract) | Seoul National University |
| Additional Authors (2nd abstract) | Bon-Chul Koo / Seoul National University |
| Presentation options (2nd abstract) | |
| Session (2nd abstract) | 10. SNe and SNRs with circumstellar interactions |
| 2nd Abstract | We have searched for near-infrared [Fe II] (1.644 $mu$m) and H$_2$ 1-0 S(1) (2.122 $mu$m) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE / UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H$_2$). Both surveys cover about 180 square degrees of the first Galactic quadrant ($7^{circ} < {it l} < 62^{circ}$; $-1.5^{circ} < {it b} < +1.5^{circ}$), and a total of 79 SNRs are falling in the survey area among the currently known 294 Galactic SNRs. The images show diffuse structures as deep as the surface brightness limit of $10^{-19}$ W m$^{-2}$ arcsec$^{-2}$ which is comparable with a $5sigma$detection limit of point sources of 18 mag. In order to inspect the narrow-band features, we subtracted {it H} and {it K}-band continuum images obtained from the UKIDSS GPS (UKIRT Infrared Deep Sky Survey of the Galactic Plane) from the [Fe II] and H$_2$ narrow-band images, respectively. By this time, we have found 19 [Fe II]- and 18 H$_2$-emitting SNRs, and these are likely to increase in future as we inspect the images in more detail. Some of the SNRs show bright, complex, and interesting structures that have never been reported in previous studies. Since [Fe II] and H$_2$ lines trace dense atomic and molecular gases associated with SNR shocks, our results can help us understand the environment and evolution of individual SNRs. Among the SNRs showing both [Fe II] and H$_2$ emission lines, some SNRs show the “[Fe II]-H$_2$ reversal'' phenomenon, i.e., the H$_2$ emission features are detected outside the [Fe II] emission boundary. This is opposite to the standard picture: If the shocks are driven by the same blast wave, we expect the H$_2$ filaments to be closer to the explosion center than the [Fe II] filaments. In this presentation, we show several examples of such SNRs detected in our study, and present high resolution ($Rsim$ 40,000) {it H} and {it K}-band spectra of H$_2$ emission features obtained by using IGRINS (Immersion Grating Infrared Spectrograph). |
Account
| First Name | Yong-Hyun |
| Last Name | Lee |
| Institution | Seoul National University |
| Country | Korea |