![[SII] Observations and what they can tell us Snippets of possibly useful stuff by](https://present5.com/presentation/69327b1d8b55e6ecaedb6006a3aaa7c7/image-1.jpg "[SII] Observations and what they can tell us Snippets of possibly useful stuff by")
[SII] Observations and what they can tell us Snippets of possibly useful stuff by Lesa Moore 31 st October 2012
![Forbidden lines n Lifetime in excited states Lyman a: 10 -8 s n [SII]:](https://present5.com/presentation/69327b1d8b55e6ecaedb6006a3aaa7c7/image-2.jpg "Forbidden lines n Lifetime in excited states Lyman a: 10 -8 s n [SII]:")
Forbidden lines n Lifetime in excited states Lyman a: 10 -8 s n [SII]: 3846 s and 1136 s n n Forbidden lines appear in low-density gas: for transitions that have long lifetimes in excited states [SII], [NII], [OIII] n where there are too few collisions to de-excite collisionally (< a few hundred thousand cc-3) n 2
Spectra on the CCD OI sky emission at 5577Å OH sky emission bands 3
Wavelength-Calibrated Galaxy Spectrum 4
Most common emission lines n “A brief introduction to narrowbanding” n http: //www. astros urf. com/bregosky/A_glimpse_to_ the_night_sky/Artic les_files/what_is. p df 5
Targets n n n Emission nebulae Planetary nebulae Supernova remnants 6
n n Exercise 3 http: //web. williams. edu/astronomy/research/P N/nebulae/exercise 3. php Ratio of intensities of [SII] lines l 6716 to l 6731 n can indicate gas density n In between, ratio describes actual gas density Low density: Ratio is statistical weight (how many electrons the level can hold) High density: Shorter lifetime (6731) makes stronger line 7
SNR in the Magellanic Clouds n n http: //www. mcsnr. org/about. aspx SNR classification - meet at least two of the following criteria: Diffuse nonthermal radio emission n Diffuse thermal X-ray emission n High [SII]/Ha ratio (> 0. 4) and/or high optical expansion velocity n 8
SNR in M 31 n n n http: //aas. org/archives/BAAS/v 25 n 2/aas 182/abs html/S 219. html High [SII]/Ha implies likely SNR Ratio is not very high for many SNRs Complementary test based on a comparison of the Ha flux and the presence or absence of hot, ionizing stars Combined BVRI, Ha, [SII] data has revealed ~200 objects which are candidate SNRs throughout M 31 based on this test 9
Optical Imaging and Spectroscopic Observation of the Galactic Supernova Remnant G 85. 9 -0. 6 n n n http: //arxiv. org/pdf/0909. 2959 v 1. pdf Images taken with narrow-band interference filters H and [SII] and their continuum. [SII]/Ha ratio image is performed n n [SII]ll 6716/6731 average flux ratio from spectra n n Ratio ~0. 42, indicating that the remnant interacts with HII regions. electron density Ne is obtained to be 395 cm− 3. [OIII]/Hb ratio n n n shock velocity has been estimated pre-shock density of nc = 14 cm− 3 explosion energy of E = 9. 2 × 1050 ergs interstellar extinction of E(B−V ) = 0. 28 neutral hydrogen column density of N(HI) = 1. 53 × 1021 cm− 2 10
Observations 11
SNR IMAGES 12
![The final image n The negative if the [SII]/Ha image of G 85. 9](https://present5.com/presentation/69327b1d8b55e6ecaedb6006a3aaa7c7/image-13.jpg "The final image n The negative if the [SII]/Ha image of G 85. 9")
The final image n The negative if the [SII]/Ha image of G 85. 9 -0. 6 (smoothed) 13
SNR SPECTRA 14
Measurements 15
Conclusions from image 16
Скачать презентацию SII Observations and what they can tell us
69327b1d8b55e6ecaedb6006a3aaa7c7.ppt