Tag Archive | quenching

New paper on active black holes affecting star formation rates!

Good news everyone, another Galaxy Zoo paper was published today! This work was led by yours truly (Hi!) and looks at the impact that the central active black holes (active galactic nuclei; AGN) can have on the shape and star formation of their galaxy. It’s available here on astro-ph: http://arxiv.org/abs/1609.00023 and will soon be published in MNRAS.

Turns out, despite the fact that these supermassive black holes are TINY in comparison to their galaxy (300 light years across as opposed to 100,000 light years!) we see that within a population of these AGN galaxies the star formation rates have been recently and rapidly decreased. In a control sample of galaxies that don’t currently have an AGN in their centre, we don’t see the same thing happening. This phenomenon has been seen before in individual galaxies and predicted by simulations but this is the first time its been statistically shown to be happening within a large population. It’s tempting to say then that it’s the AGN that is directly causing this drop in the star formation rate (maybe because the energy thrown out by the active black hole blasts out or heats the gas needed to fuel star formation) but with the data we have we can’t say for definite if the AGN are the cause. It could be that this drop in star formation is being caused by another means entirely, which also coincidentally turns on an AGN in a galaxy.

fig1

A random sample of galaxies which host a central active black hole used in this work. The disc vote fraction classification from Galaxy Zoo 2 is shown for each image. Images from SDSS.

These galaxies were also all classified by our wonderful volunteers in Galaxy Zoo 2 which meant that we could also look whether this drop in the star formation rate was dependent on the morphology of the galaxy; turns out not so much! If the drop in the star formation rate is being caused directly by the AGN (and remember we still can’t say for sure!) then the central black hole of a galaxy doesn’t care what shape galaxy it’s in. An AGN will affect all galaxies, regardless of morphology, just the same.

 

 

Galaxy Zoo Quench – Experience the Full Scientific Process

Experience Science from Beginning to End! Classify, Analyze, Discuss, and Collaboatively Write an Article!

Galaxy Zoo and other Zooniverse projects have given thousands the opportunity to contribute to scientific research.  It’s time to take the role of volunteers to the next level.  For the next two months*, this new Galaxy Zoo Quench project provides the opportunity to take part in the ENTIRE scientific process – everything from classifying galaxies to analyzing results to collaborating with astronomers to writing a scientific article!

Galaxy Zoo Quench will examine a sample of galaxies that have recently and abruptly quenched their star formation. These galaxies are aptly named Post-Quenched Galaxies.  They provide an ideal laboratory for studying how galaxies evolve from blue, star-forming spiral galaxies to red, non-star-forming elliptical galaxies. Using the more than a million galaxies in the Sloan Digital Sky Survey, we identified ~3000 post-quenched galaxies.  By classifying these galaxies and analyzing the results, we will explore the mechanisms that quenched their star formation and investigate the role of post-quenched galaxies in galaxy evolution.

The entire process of classifying, analyzing, discussing, and writing the article will take place over an 8 week period*, beginning July 18th. After classifying the galaxies, volunteers will use the tools available within Zooniverse to plot the data and look for trends.  Through reading articles and interaction in Talk, volunteers will gain background information. Throughout, they’ll discuss with the science team their interpretation of the results.  At the end of the process, volunteers and the science team will collaboratively write a 4-page Astrophysical Journal article.

Large Arms 3

What causes the star formation in these galaxies to be quenched?  How do interactions impact galaxy evolution?  What is the fate of our Milky Way?  Join us this Summer (or Winter if you’re below the equator!) in exploring these questions, being a part of the scientific process, and contributing to our understanding of this dynamic phase of galaxy evolution!

Tidal Stream

CLICK HERE TO PARTICIPATE!

We’ll be sharing more details about this project during the next Galaxy Zoo Hangout, on Monday, July 15th at 14:00 CST / 19:00 GMT / 20:00 BST. Have questions about the project? Post them here or tweet at us (@galaxyzoo). Just before the Hangout starts, we’ll embed the video here so you can watch from the blog.

The best way to send us a comment during the live Hangout is through twitter (@galaxyzoo). You can also leave a comment on this blog post, or on Google Plus, Facebook or YouTube. See you soon!

Update: here’s the hangout (and the mp3 version)!

*Note: science timelines often subject to a factor of two uncertainty. We’ll do our best to keep on track, at the same time expecting the unexpected (all part of the fun of doing science!).