Round 2: Welcome Back!

We’re back! After a successful first round last December, we are relaunching the Andromeda Project for a second round of cluster finding in our galaxy neighbor, Andromeda (aka: M31). More than 10,000 volunteers pitched in during Round 1 to search about 80% of the Panchromatic Hubble Andromeda Treasury (PHAT) survey imaging. The Hubble Space Telescope (HST) was able to image the remaining portions of the galaxy over the past year, completing a >3 year effort to survey Andromeda on October 12th. In Round 2, we will complete our cluster search of the remaining PHAT images as well as search other Hubble images of M31, which I will talk about a bit more later on.

Previously on this blog I’ve talked about the results we’ve been able to derive, thanks to the efforts of the AP community, but I wanted to emphasize again how invaluable everyone’s participation has been. Using the first round identifications, we constructed a star cluster catalog containing almost 3000 star clusters, representing a 10x increase over previous catalogs of that portion of Andromeda. The quality of this catalog has allowed us to start answering questions about how clusters form and evolve within the galaxy.

Andromeda Project search regions: PHAT survey (white) and archival images (red). Image Credit: Robert Gendler

In Round 2, we include two sets of Andromeda images: the final PHAT images and images obtained from the HST archive. The PHAT images we feature this round are 1) those that were observed in the past year (or past month, even!) and 2) images that stretch out to the limits of the survey. You may encounter blank, black portions of images during your searching. No need to worry – these parts of the image represent portions of sky not imaged as part of the survey. Also, you might occasionally encounter a synthetic cluster – an object that we’ve added into the images. As Matt talked about in last week’s blog post, these synthetic clusters are crucial to helping us understand what objects we can and cannot detect.

So, how about the other set of images?  What is the HST archive?  The Space Telescope Science Institute (STSci), who operates Hubble, hosts a website called the Barbara A. Mikulski Archive for Space Telescopes (MAST) where data from space observatories like Hubble (and other notable missions such as Kepler and GALEX) are stored. This archive is critically important to astronomers, allowing them to find and use images or spectra that were obtained by instruments on Hubble.

Every observation taken by HST is stored and made publicly available, ensuring that they can be used for science in the future. The open availability of these data allow observations to be used by multiple researchers, sometimes in ways that were not originally anticipated. The Andromeda Project is a perfect example of this repurposing: the archival images we include in Round 2 are images obtained as part of an observing program to follow-up on candidate gravitational microlensing events detected within M31. Now we can reuse these images to assist in our study of star clusters!

Remember: these images are publicly available to anyone.  That means you! The folks at MAST host a website called the Hubble Legacy Archive (HLA) that provides users an interface to search and view archival images. For an introduction to the HLA, check out this page. Many of our PHAT images are already available for browsing and download through the HLA as well.  Try searching for “M31”; some of my other favorites include “M82” or the “Antennae”.

On behalf of the whole Andromeda Project team, I thank you for your interest and assistance.  Be sure to sign in when you visit andromedaproject.org and let’s go find some clusters!

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