1 / 16

[SII] Observations and what they can tell us

[SII] Observations and what they can tell us. Snippets of possibly useful stuff by Lesa Moore 31 st October 2012. Forbidden lines. Lifetime in excited states Lyman a : 10 -8 s [SII]: 3846 s and 1136 s Forbidden lines appear in low-density gas:

vivian-kirkland
Download Presentation

[SII] Observations and what they can tell us

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. [SII] Observations and what they can tell us Snippets of possibly useful stuff by Lesa Moore 31st October 2012

  2. Forbidden lines • Lifetime in excited states • Lyman a: 10-8 s • [SII]: 3846 s and 1136 s • Forbidden lines appear in low-density gas: • for transitions that have long lifetimes in excited states [SII], [NII], [OII], [OIII] • where there are too few collisions to de-excite collisionally (< a few hundred thousand cc-3)

  3. Spectra on the CCD OI sky emission at 5577Å OH sky emission bands

  4. Wavelength-Calibrated Galaxy Spectrum

  5. Most common emission lines • “A brief introduction to narrowbanding” • http://www.astrosurf.com/brego-sky/A_glimpse_to_the_night_sky/Articles_files/what_is.pdf

  6. Targets • Emission nebulae • Planetary nebulae • Supernova remnants

  7. Exercise 3 In between, ratio describes actual gas density • http://web.williams.edu/astronomy/research/PN/nebulae/exercise3.php • Ratio of intensities of [SII] lines • l6716 to l6731 • can indicate gas density Low density: Ratio is statistical weight (how many electrons the level can hold) High density: Shorter lifetime (6731) makes stronger line

  8. SNR in the Magellanic Clouds • http://www.mcsnr.org/about.aspx • SNR classification - meet at least two of the following criteria: • Diffuse nonthermal radio emission • Diffuse thermal X-ray emission • High [SII]/Ha ratio (> 0.4) and/or high optical expansion velocity

  9. SNR in M31 • http://aas.org/archives/BAAS/v25n2/aas182/abshtml/S219.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 M31 based on this test

  10. Optical Imaging and Spectroscopic Observation of the GalacticSupernova Remnant G85.9-0.6 • http://arxiv.org/pdf/0909.2959v1.pdf • Images taken with narrow-band interference filters H and [SII] and their continuum. • [SII]/Ha ratio image is performed • Ratio ~0.42, indicating that the remnant interacts with HII regions. • [SII]ll6716/6731 average flux ratio from spectra • electron density Ne is obtained to be 395 cm−3. • [OIII]/Hb ratio • 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

  11. Observations

  12. SNR IMAGES

  13. The final image • The negative if the [SII]/Ha image of G85.9-0.6 (smoothed)

  14. SNR SPECTRA

  15. Measurements

  16. Conclusions from image

More Related