October 25, 2013 Grant Justis

Frontier Fields Hangout Highlights

For those who would rather not sit through the whole hangout (and I really can’ t imagine why you wouldn’t since it was very interesting), I’ve taken the time to index some of the more interesting topics discussed during the hour. Click on the topic below to go to that part of the hangout.

Please stay tuned for more Hubble Hangouts on the Frontier Fields as the project progresses. We are planning more hangouts that discuss the role of dark matter in the Frontier Fields clusters, how to get the data yourself from the Hubble archive, and much more!

October 25, 2013 Grant Justis

Supernova Discovered in One of the Frontier Fields

The data had hardly started coming through the pipeline when astronomers made the first Frontier Field discovery: a supernova in the galaxy cluster MACSJ0717, one of the first of the Frontier Fields to be imaged.

The Frontier Fields designation for this object is SN HFF13Zar, and its nickame is “SN Zara.”

Supernovae discovery is an offshoot of Frontier Fields science because Hubble will be revisiting many of these fields several times over the next three years, allowing astronomers to compare recent images with older ones, and look for things that are different.

The supernova is located 1.73 arcmin from the center of the MACSJ0171 cluster and is a whopping 23.53 (+- 0.05) magnitude.

I say whopping, but big numbers on the magnitude scale mean an object is very, very dim. This is definitely a faint supernova, but not out of the ordinary in terms of what Hubble can see. Hubble can see things as faint as 31st magnitude, which is slightly fainter than objects that can be viewed by the best ground-based telescopes.

Without getting too crazy into the magnitude scale topic, suffice it to say for our purposes that

One magnitude thus corresponds to a brightness difference of exactly the fifth root of 100, or very close to 2.512 — a value known as the Pogson ratio. Source: Sky and Telescope

Aren’t you glad you asked?

So the supernova is faint, but Hubble can see it without problems, as you can tell from the right panel, in which a purple circle marks the supernova. The left panel in this image is a compilation of observations taken in 2006 and prior with Hubble’s Advanced Camera for Surveys (ACS).

SN HFF12Zar was discovered using the F814W filter, known as the i band in the ACS.

The supernova’s home is still unknown — it could have occurred in one of three potential galaxies within 5 arcsec of the stellar explosion. These galaxies are labelled in the above image as A (orange), B (red) and C (light blue).

The other circles, D (green) and E (yellow) are other galaxies probably not associated with the supernova.

The redshift of the galaxy cluster is z=0.5458 (~10 billion LY away) and according to Dr. Steven Rodney (JHU), Dr. Jennifer Lotz (STScI), and Dr. Louis-Gregory Strolger (STScI), if the supernova is associated with host galaxy candidates A or B, it is a foreground object. If it’s associated with host galaxy candidate C, then it could plausibly be a SN from a galaxy in the outskirts of the cluster.

We’ll be revisiting this cluster again with Hubble in December 2013, as part of the Grism Lens Amplified Survey from Space (GLASS) proposal, but this supernova will probably be faded by the time Hubble looks this way again. However Steve Rodney and Lou Strolger have a program to search the Frontier Fields data for new supernovae as it comes in; if they find something that is potentially very interesting — very distant and/or lensed by the cluster, they will trigger extra Hubble observations of the supernovae to determine the type of supernova and exact distance.

October 18, 2013 Space Telescope Science Institute

First Hubble Hangout Featuring Frontier Fields

Please join us for our first Hubble Hangout that features the Frontier Fields Survey.

A collaboration of astronomers are poised to make observations with the Hubble Space Telescope that will provide us with the deepest views we’ve ever had of the cosmos and give us a glimpse of what the James Webb Space Telescope will routinely provide us.

Known as the Frontier Fields survey, this revolutionary deep field program will combine the power of the Hubble Space Telescope with the natural gravitational telescopes of high-magnification clusters of galaxies. Using both the Wide Field Camera 3 and Advanced Camera for Surveys in parallel, HST will produce the deepest observations of clusters and their lensed galaxies ever obtained, and the second-deepest observations of blank fields (located near the clusters).

These images will reveal distant galaxy populations ~10-100 times fainter than any previously observed, improve our statistical understanding of galaxies during the epoch of reionization, and provide unprecedented measurements of the dark matter within massive clusters.

The Frontier Field Survey will be pushing the limits of our beloved space telescope, making it more powerful than ever before, and providing us with some of the most important images ever taken.

Our goal is to have more of these as the project progresses, so please follow our g+ page to learn about future hangouts as they are scheduled.