No, these aren't "new SNRs" in the sense that they've just appeared. These newly identified SNRs have just escaped detection in previous radio, X-ray, and optical surveys. With the increased sensitivity, complete coverage, and digital nature of the MCELS dataset, made even more powerful when combined with recent sensitive X-ray observations from ROSAT, we can identify the SNRs that previous surveys have missed.

Our goal is to provide a complete sample of the conventional SNRs in both Magellanic Clouds. Such a sample will allow for the study of the global characteristics of SNRs as well as to provide a greater range of individual SNRs and environmental conditions for detailed study.

The Growing List

• N9 and N4 SNRs

  The first identifications came from a combination of emission-line imaging and ROSAT PSPC data. Two extended sources were identified in the PSPC data. These were found to be coincident with two nebulae with high [S II] to Halpha ratios, showing them to be two previously unidentified SNRs!

  Below is an 3-color optical image of the field, where red is Halpha, green is [S II], and blue is [O III]. The large green arc in the upper left is the newly identified SNR N4, or 0454-672. The SNR N9, aka 0453-669, is the region of green filaments just to the right (outside) of the large bubble in the lower right.

  

  For more details, check out
  "Two New Supernova Remnants in OB Associations in the Large Magellanic Cloud" Smith, R.C., Chu, Y.-H., Mac Low, M.-M., Oey, M.S., Klein, U. 1994, AJ, 108, 1266

• The Honeycomb SNR

  For more details, check out
  "The Honeycomb Supernova Remnant", Chu, Y.-H., Dickel, J.R., Staveley-Smith, L., Osterberg, J., Smith, R.C. 1995, AJ, 109, 1729

• The N159 SNR

  For more details, check out
  "Uncovering a Supernova Remnant Hidden Near LMC X-1", Chu, Y.-H., Kennicutt, R.C., Snowden, S.L., Smith, R.C., Williams, R.M., & Bomans, D.J. 1997, PASP, May issue, in press.

• The N44 SNR

  Details coming soon to this Web page!

How do we identify SNRs?

Optical Emission-line signature

Ratio of [SII] to Halpha flux > 0.4.

X-ray signature

Generally are bright extended soft X-ray sources.

Radio signature

Non-thermal radio spectrum!

The MCELS project has been supported in part by NSF grants AST-9540747 and AST-0307613, and through the generous support of the Dean B. McLaughlin Fund at the University of Michigan, a bequest from the family of Dr. Dean B. McLaughlin in memory of his lasting impact on Astronomy. The National Optical Astronomy Observatory is operated by the Association of Universities for Research in Astronomy Inc. (AURA), under a cooperative agreement with the National Science Foundation.

This Web page is maintained by Chris Smith and Roger Leiton at Cerro Tololo Inter-American Observatory. Please send comments, suggestions, or reports of any problems to csmith@ctio.noao.edu.

Last update: January 9, 2006 by RCS