P13: Emission Line Mapping

Observing Goals:

Make observations using narrow band filters in several lines: \({\rm H_{\alpha}}\), \({\rm H_{\beta}}\), \({\rm [OIII]}\), and \({\rm [SII]}\) of an emission line system. Calibrate the narrow band observations, with broad band observations to remove continuum emission. Produce maps of line emission and emission line ratios in your target object. Useful Background and References:

  • Osterbrock

  • R3. Line Emission from Narrow Band Observations

Observation Planning:

  • Observation Time

    • You will be observing HALF a night.

  • Target Selection

    • You should select an object that is of suitable size, and bright in emission lines (such as certain nebulae), that will be at a low airmass during your observation time.

  • Observations

    • You should observe your object as deeply as possible in all avaialble narrow band filters, and the broad band filters that correspond to the same portions of the spectrum. Note you will need many more observations in the narrow bands to achieve high signal to noise. Come up with a strategy where you observe a sequence mixing the filters as you go to ensure a good mix during your observation period.

    • You should observe at least one standard star field with multiple stars so that you can both calibrate the magnitudes of the stars and use continuum sources (stars) to calibrate the line emission in the filters.

Data Analysis:

  • Data Reduction Basic Steps

    • Visit the page Data Reduction Cheat Sheet.

    • Reduce the images to remove the systematic effects.

    • Carefully align and combine observations in each filter to produce the highest signal to noise images possible.

  • Further for this project

    • Look at the guide R03. Line Emission from Narrow Band Observations to remove the continuum light from your observations and produce Narrow Line images in the four narrow lines observed

  • Further Analysis for this project

    • Further, make line ratio maps between each pair of lines (e.g. \({\rm H_{\alpha}/H_{\beta}}\), \({\rm H_{\alpha}/[SII]}\), etc…)

    • You can produce multi-colour images using various lines or line ratios to highlight the features that you find in your object.

Results:

Can you answer these questions with your work?

  • Q1: What features do you observe in the emission line maps from your source?

  • Q2: Do you notice different features in the line ratio maps?

  • Q3: Can you explain the physical meaning between changes in line rations you observed? e.g. with Temperature, Density or Pressure sensitive ratios?

Presenting your results: