The First H-alpha LV Plots

A huge breakthrough in looking at our data came when my advisor, Bob Benjamin, found a program called GHESS, written by David Nidever at the University of Virginia. His program, among a host of other things, makes LV plots. This alone is pretty standard; however, it does them in a special way. The code can be used to make LV diagrams that show either the area of gaussians from the data or the latitude as a function of color, making them three-dimensional in a sense. Below are a good sampling of the plots I made with GHESS, along with an explanation as to why each helps us study the galactic structure of our universe.

The first four plots are LV diagrams of either H-alpha or neutral hydrogen, with the color scaling showing gaussian areas of the reduced spectra.

Fig. 3: H-alpha, l= 0°-360°, b= ±30°.

Fig. 4: H-alpha, l= 0°-360°, b= ±5°.

The strip with no data in the above diagram is due to a velocity calibration issue in the H-alpha data and should be corrected in the near future to provide a full LV diagram.

Fig. 5: Neutral Hydrogen, l= 0°-360°, b= ±30°.

Fig. 6: Neutral Hydrogen, l= 0°-360°, b= ±5°.

The next four plots are again LV diagrams of either H-alpha or neutral hydrogen; however, this time the color scaling shows galactic latitude.

Fig 7: H-alpha, l= 0°-360°, b= ±30°.

Fig. 8: H-alpha, l= 0°-360°, b= ±5°.

Neutral Hydrogen, l= 0°-360°, b= ±30°.

Neutral Hydrogen, l= 0°-360°, b= ±5°.

The last plot is another LV diagram showing color scaling with gaussian area, but this time using carbon monoxide (CO).

Carbon Monoxide (CO), l= 0°-360°, b= ±5°.

LV Diagrams we're already a pretty standard diagram for looking at intragalactic structure. Now, we can not only view LV diagrams as spatial plots, but can view them as either two dimensional spatial plots that also show intensity, for three dimensional spacial plots. Using the plots that show gaussian area with color, we can tell how intese the H-alpha is at some velocity. If we pair this with the LV diagram that shows the latitude varying with color, it can be extremely helpful in locating structure because we know where the object is in all three spacial dimensions, and also can look for patterns in intensity to know if it's a cohesive structure.

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Useful links

The following links are very useful for looking up info on UNIX, web page making, and astrophysical data and journals.

SIMBAD (Stellar/Galactic database)

NED (Extragalactic database)

UNIX tutorial

Web page basics

NASA Astrophysics Data Service