HEIC: A Scattering of Spiral and Elliptical Galaxies

[bystander]

A Scattering of Spiral and Elliptical Galaxies
ESA/HEIC Hubble Picture of the Week | 2013 Sep 23

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This image shows the massive galaxy cluster MACS J0152.5-2852, captured in detail by the NASA/ESA Hubble Space Telescope's Wide Field Camera 3. Almost every object seen here is a galaxy, each containing billions of stars. Galaxies are not usually randomly distributed in space, but instead appear in concentrations of hundreds, held together by their mutual gravity. Elliptical galaxies, like the yellow fuzzy objects seen in the image, are most often found close to the centres of galaxy clusters, while spirals, such as the bluish patches, are usually found to be further out and more isolated.

A version of this image obtained tenth prize in the Hubble's Hidden Treasures image processing competition, entered by contestant Judy Schmidt.

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

<< Previous ESA/HEIC Hubble POTW

[geckzilla]

I remember being confused by some small dots in this image which I presume to be rather faint local stars rather than distant galaxies. I couldn't figure out why they weren't aligned with the rest of the image. I ended up deciding they must have moved between exposures since the IR and ACS data are six years apart. I guess that conclusion wasn't totally wrong but the movement is probably caused by parallax rather than actual location displacement. It would have helped to know about parallax earlier.

[neufer]

A Scattering of Spiral and Elliptical Galaxies
ESA/HEIC Hubble Picture of the Week | 2013 Sep 23

A version of this image obtained tenth prize in the Hubble's Hidden Treasures image processing competition,
entered by contestant Judy Schmidt.

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

I remember being confused by some small dots in this image which I presume to be rather faint local stars rather than distant galaxies. I couldn't figure out why they weren't aligned with the rest of the image. I ended up deciding they must have moved between exposures since the IR and ACS data are six years apart. I guess that conclusion wasn't totally wrong but the movement is probably caused by parallax rather than actual location displacement. It would have helped to know about parallax earlier.

What does one get for tenth prize

• First Prize – 1 Week on a canal boat donated by Wyvern Shipping Co Ltd.
  Second Prize – Day boat hire donated by Grebe Canal Cruises
  Third Prize - £100 Cash Prize donated by Mr & Mrs B Martin
  Fourth Prize – Balloon Flight with Virgin Balloon Flights.
  Fifth Prize – Swarovski Crystal Necklace.
  Sixth Prize – Garden Centre Voucher - £25
  Seventh Prize – Wendover Trust Fruit Cake
  Eighth Prize – Boots Hairdryer
  Ninth Prize - Ladies Handbag
  Tenth Prize – Tiger Cub Fleece Throw.

[geckzilla]

Everyone got a poster and DVD. I also received some postcards which weren't mentioned in the prize list, though.

[neufer]

Everyone got a poster...

I hope it wasn't "beyond".

[geckzilla]

No, that's your sidekick. I got actual paper posters.

[Ann]

Some (or all?) of the bluest galaxies must be lensed. There is an extremely red galaxy in the picture too, which is most obviously lensed.

Ann

[geckzilla]

A lot of the MACS (MAssive Cluster Survey) objects have obvious lensing. I thought it was actually rather subtle in this one, though.

[Ann]

http://www.spacetelescope.org/images/potw1338a/ wrote:

Elliptical galaxies, like the yellow fuzzy objects seen in the image, are most often found close to the centres of galaxy clusters, while spirals, such as the bluish patches, are usually found to be further out and more isolated.

So the blue spirals should be further from the cluster center than the ellipticals. But in this picture, a string of blue galaxies are seen crossing the middle of the picture, apparently right across the cluster center. The galaxies are fluffy and large-looking and some of them seem rather irregular. In my amateur opinion, there is no way that several large, fluffy, irregular-looking spirals could be situated near the center of a cluster that is otherwise populated mostly by ellipticals.

If the blue galaxies are lensed background objects, we get an explanation for their irregular shapes, large sizes and positions near the cluster center. They have been lensed and magnified by the gravity of the cluster.

By the way, it is a nice picture, geckzilla.

Ann

[geckzilla]

The only way to get a good estimate for how far out they are from the cluster would be to look at the redshift. There is just no way to make any accurate judgment based ln visual clues alone. And you would need to look at more than just this picture to back up your idea that some strong lensing is actually magnifying the background.