Jump to content

Banner2.jpg.35fd74882a15b2b8a1b4142f7dcc8bed.jpg

Where to find edge-on Galaxy spectra that can be used to calculate Galaxy Rotation Curves?


Recommended Posts

Hi Guys,

Do you know where I can find spectra of edge-on galaxies (or highly inclined galaxies) with regular spectra taken along the galactic axis that I can use to calculate galactic rotation curves?

Thanks

Steve.

Link to comment
Share on other sites

Hi Steve,

There are several examples of this measurement by amateurs on the ARAS forum. The observers might still have the spectra. Otherwise perhaps contact the authors of papers where rotation curves measured using optical spectroscopy have been published ? (I think most of them use radio astronomy so you can measure further out than you can do at visible wavelengths)

https://www.spectro-aras.com/forum/viewtopic.php?f=6&t=2618

https://www.spectro-aras.com/forum/viewtopic.php?f=6&t=2232

http://www.astrosurf.com/buil/UVEX4/_demo_m82.jpg

https://www.spectro-aras.com/forum/viewtopic.php?f=6&t=2420

http://www.spectro-aras.com/forum/viewtopic.php?f=6&t=1682

http://www.astrosurf.com/buil/forum/ngc7331_poster.png

Cheers

Robin

  • Like 1
Link to comment
Share on other sites

For exactly edge on galaxies the conversion to a rotation curve  is not  straightforward though as at any given location, the spectrum is potentially a combination of regions at different radii, each seen with a different component velocity in our direction. 

  • Like 1
Link to comment
Share on other sites

39 minutes ago, robin_astro said:

This one of M77 is what I imagined it would look like, but with an ALPY?  It says T200, is that the same as the ALPY 200 grating that you talk about?  I can't even imagine it has that resolution! 

40 minutes ago, robin_astro said:

But this one, with an ALPY 600 (no doubt this time) it's tilted the slit along the axis of the galaxy.  A much better idea.

So either way Alpy cuts it here, it doen't need an LHIRES III, or even a DADOS, as I was suggesting in the other thread.

28 minutes ago, robin_astro said:

For exactly edge on galaxies the conversion to a rotation curve  is not  straightforward though as at any given location, the spectrum is potentially a combination of regions at different radii, each seen with a different component velocity in our direction. 

Good point.

So basically, if I save up for an ALPY 600, it's good enough to produce one of these curves, is that right?

Great.

Kind regards.

Steve

Link to comment
Share on other sites

Just now, SteveBz said:

This one of M77 is what I imagined it would look like, but with an ALPY?  It says T200, is that the same as the ALPY 200 grating that you talk about?  I can't even imagine it has that resolution! 

But this one, with an ALPY 600 (no doubt this time) it's tilted the slit along the axis of the galaxy.  A much better idea.

So either way Alpy cuts it here, it doen't need an LHIRES III, or even a DADOS, as I was suggesting in the other thread.

Good point.

So basically, if I save up for an ALPY 600, it's good enough to produce one of these curves, is that right?

Great.

Kind regards.

Steve

Then I can use it with the f/4.4, small, light-weight Newtonian (It's a small Bresser 114 mm x 500 mm) and not worry about the Meade ETX90.  It doesn't seem very difference in price. Both about 2k for the full kit.

Link to comment
Share on other sites

T200 is the telescope (0.2m aperture).  Rotation velocities are quite high so you don't need particularly high resolution. An f4.5 Newtonian is a good choice with the ALPY.  A much better match for an ALPY than the slow etx90. 114mm aperture is rather small  for  objects as faint as this though and exposures are long even with bigger apertures (2 hours in 20min exposures say) so you will need a good mount with good guiding

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.