[sii] observations and what they can tell us

[SII] Observations and [SII] Observations and what they can tell uswhat they can tell us

Snippets of possibly useful Snippets of possibly useful stuff by Lesa Moorestuff by Lesa Moore

3131stst October 2012 October 2012

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Forbidden linesForbidden lines

Lifetime in excited statesLifetime in excited states Lyman Lyman : 10: 10-8-8 s s [SII]: 3846 s and 1136 s[SII]: 3846 s and 1136 s

Forbidden lines appear in low-density Forbidden lines appear in low-density gas:gas: for transitions that have long lifetimes in for transitions that have long lifetimes in

excited states [SII], [NII], [OII], [OIII]excited states [SII], [NII], [OII], [OIII] where there are too few collisions to de-where there are too few collisions to de-

excite collisionally (< a few hundred excite collisionally (< a few hundred thousand ccthousand cc-3-3))

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Spectra on the CCDSpectra on the CCD

OI sky emission at 5577Å

OH sky emission bands

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Wavelength-Calibrated Galaxy Wavelength-Calibrated Galaxy SpectrumSpectrum

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Most common emission Most common emission lineslines

““A brief A brief introduction to introduction to narrowbanding”narrowbanding” http://www.astrohttp://www.astro

surf.com/brego-ssurf.com/brego-sky/A_glimpse_toky/A_glimpse_to_the_night_sky/A_the_night_sky/Articles_files/whatrticles_files/what_is.pdf_is.pdf

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TargetsTargets

Emission Emission nebulaenebulae

Planetary Planetary nebulaenebulae

SupernovSupernova a remnantsremnants

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Exercise 3Exercise 3 http://web.williams.edu/astronomy/reseahttp://web.williams.edu/astronomy/resea

rch/PN/nebulae/exercise3.phprch/PN/nebulae/exercise3.php Ratio of intensities of [SII] lines Ratio of intensities of [SII] lines

6716 to 6716 to 67316731 can indicate gas densitycan indicate gas density

Low density: Ratio is statistical weight (how many electrons the level can hold)

High density: Shorter lifetime (6731) makes stronger line

In between, ratio describes actual gas density

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SNR in the Magellanic SNR in the Magellanic CloudsClouds

http://www.mcsnr.org/about.aspxhttp://www.mcsnr.org/about.aspx

SNR classification - meet at least two SNR classification - meet at least two of the following criteria:of the following criteria: Diffuse nonthermal radio emission Diffuse nonthermal radio emission Diffuse thermal X-ray emissionDiffuse thermal X-ray emission High [SII]/HHigh [SII]/H ratio (> 0.4) and/or high ratio (> 0.4) and/or high

optical expansion velocity optical expansion velocity

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SNR in M31SNR in M31 http://aas.org/archives/BAAS/v25n2/aas18http://aas.org/archives/BAAS/v25n2/aas18

2/abshtml/S219.html2/abshtml/S219.html

High [SII]/HHigh [SII]/H implies likely SNR implies likely SNR Ratio is not very high for many SNRs Ratio is not very high for many SNRs Complementary test based on a Complementary test based on a

comparison of the Hcomparison of the Hflux and the flux and the presence or absence of hot, ionizing starspresence or absence of hot, ionizing stars

Combined BVRI, HCombined BVRI, H, [SII] data has , [SII] data has revealed ~200 objects which are revealed ~200 objects which are candidate SNRs throughout M31 based on candidate SNRs throughout M31 based on this testthis test

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Optical Imaging and Optical Imaging and Spectroscopic Observation of Spectroscopic Observation of

the Galacticthe GalacticSupernova Remnant G85.9-0.6Supernova Remnant G85.9-0.6 http://arxiv.org/pdf/0909.2959v1.pdfhttp://arxiv.org/pdf/0909.2959v1.pdf

Images taken with narrow-band interference Images taken with narrow-band interference filters H and [SII] and their continuum. filters H and [SII] and their continuum.

[SII]/H[SII]/H ratio image is performed ratio image is performed Ratio ~0.42, indicating that the remnant interacts with Ratio ~0.42, indicating that the remnant interacts with

HII regions. HII regions. [SII][SII]6716/6731 average flux ratio from spectra6716/6731 average flux ratio from spectra

electron density Nelectron density Nee is obtained to be 395 cm is obtained to be 395 cm−3−3. . [OIII]/H[OIII]/H ratio ratio

shock velocity has been estimatedshock velocity has been estimated pre-shock density of npre-shock density of ncc = 14 cm = 14 cm−3−3

explosion energy of E = 9.2 × 10explosion energy of E = 9.2 × 105050 ergs ergs interstellar extinction of E(B−V ) = 0.28interstellar extinction of E(B−V ) = 0.28 neutral hydrogen column density of N(HI) = 1.53 × 10neutral hydrogen column density of N(HI) = 1.53 × 102121

cmcm−2−2

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ObservationsObservations

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SNR IMAGESSNR IMAGES

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The final imageThe final image

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

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SNR SPECTRASNR SPECTRA

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MeasurementsMeasurements

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Conclusions from imageConclusions from image