science

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Team Update: Additions to Guide Info

Started by lcjohnso
Default_user
almost 7 years ago

Are you curious about why some clusters look different than others? Wondering what’s up with the bright stars? The Guide (http://www.andromedaproject.org/#!/guide) is the best place to start. There we've provided lots of information about clusters, galaxies, and provide plenty of image classification examples.

If you find something you still can’t explain, be sure to tag the image (I suggest: #weird) and start a discussion. Or if you find something you can't categorize as either cluster, galaxy, or artifact, use a hashtag in Talk for those as well (maybe: #hii or #interesting with an explanation why).

Now I wanted to follow-up on items -not- discussed in the Guide that participants have pointed out or asked about. First, from today's blog entry:

1) Dust Lanes: Many people have asked about “sinuous dust lanes” that appear as darker patches in the color images. Indeed, these are caused by the attenuation of light by filaments of dust in Andromeda that are situated between the majority of the stars in the galaxy’s disk and our viewing location. This dust will block more of the blue light than red light, so the presence of dust can be detected as regions where all of the stars are much redder or dimmer than their surroundings. These structures are typically large and extended, making it hard to understand what is going on at the small scale of the Andromeda Project’s search images. Check out this image example (http://blog.andromedaproject.org/2012/12/10/first-week-faqs/ap_dust/) of a large area cutout from our Hubble Space Telescope imaging. This image provides a good example of what these dust filaments look like on larger scales.

And a few others...

2) Black Dots, Yellow Dashes, and Other Small Artifacts: On the first day, a number of people pointed out small black dots (including here: http://talk.andromedaproject.org/objects/AAP00004m9/discussions/DAP10009m1) as well as yellow streaks or dashes along chip gaps. These all fall under the category of image artifacts - they are small imperfections in the images due to hot or saturated pixels and cosmic rays.

3) Image Gradients: In the central regions of Andromeda, the brightness of the disk changes very rapidly as we move towards the nucleus. This rapid change often causes the images to look poor, as no single brightness and contrast setting will work for the whole image. Fortunately, only a small number of images are affected by this issue, so please try to do your best but don't worry too much about these isolated frames.

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