Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When galaxies switch off

01.08.2013
Hubble's COSMOS survey solves "quenched" galaxy mystery

Some galaxies hit a point in their lives when their star formation is snuffed out, and they become "quenched". Quenched galaxies in the distant past appear to be much smaller than the quenched galaxies in the Universe today.


Sample of non-star-forming galaxies from the COSMOS survey
Image credit: NASA, ESA, M. Carollo (ETH Zurich)

This has always puzzled astronomers — how can these galaxies grow if they are no longer forming stars? A team of astronomers has now used a huge set of Hubble observations to give a surprisingly simple answer to this long-standing cosmic riddle.

Until now, these small, snuffed-out galaxies were thought to grow into the larger quenched galaxies we see nearby.

As these galaxies are no longer forming new stars, they were thought to grow by colliding and merging with other smaller quenched galaxies some five to ten times less massive. However, these mergers would require many such small galaxies floating around for the quenched population to snack on — which we do not see.

Until recently it had not been possible to explore a sufficient number of quenched galaxies, but now a team of astronomers has used observations from the Hubble COSMOS survey to identify and count these switched-off galaxies throughout the last eight billion years of cosmic history.

"The apparent puffing up of quenched galaxies has been one of the biggest puzzles about galaxy evolution for many years," says Marcella Carollo of ETH Zurich, Switzerland, lead author on a new paper exploring these galaxies. "No single collection of images has been large enough to enable us to study very large numbers of galaxies in exactly the same way — until Hubble's COSMOS," adds co-author Nick Scoville of Caltech, USA.

The team used the large set of COSMOS images [1], alongside additional observations from the Canada–France–Hawaii Telescope and the Subaru Telescope, both in Hawaii, USA, to peer back to when the Universe was less than half its present age. These observations mapped an area in the sky almost nine times that of the full Moon.

The quenched galaxies seen at these times are small and compact — and surprisingly, it seems they stay that way. Rather than puffing up and growing via mergers over time, these small galaxies mostly keep the size they had when their star formation switched off [2]. So why do we see these galaxies apparently growing larger over time?

"We found that a large number of the bigger galaxies instead switch off at later times, joining their smaller quenched siblings and giving the mistaken impression of individual galaxy growth over time," says co-author Simon Lilly, also of ETH Zurich. "It's like saying that the increase in the average apartment size in a city is not due to the addition of new rooms to old buildings, but rather to the construction of new, larger apartments," adds co-author Alvio Renzini of INAF Padua Observatory, Italy.

This tells us a lot about how galaxies have evolved over the last eight billion years of the Universe's history. It was already known that actively star-forming galaxies were smaller in the early Universe, explaining why they were smaller when their star formation first switched off.

"COSMOS provided us with simply the best set of observations for this sort of work — it lets us study very large numbers of galaxies in exactly the same way, which hasn't been possible before," adds co-author Peter Capak, also of Caltech. "Our study offers a surprisingly simple and obvious explanation to this puzzle. Whenever we see simplicity in nature amidst apparent complexity, it's very satisfying," concludes Carollo.

Notes

[1] In making the COSMOS survey, Hubble photographed 575 slightly overlapping views of the Universe using the Advanced Camera for Surveys (ACS) aboard Hubble. It took nearly 1000 hours of observations and is the largest project ever conducted with Hubble. This survey has proved invaluable; it has helped to map dark matter in 3D (heic0701), to further understand the effects of gravitational lensing (heic0806), and to characterise the expansion of the Universe (heic1005).

[2] There is still the possibility of growth via mergers for a fraction of this quenched population, but not a majority, as previously thought.

Notes for editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The research is presented in a paper entitled “Newly-quenched galaxies as the cause for the apparent evolution in average size of the population”, for publication in The Astrophysical Journal.

[1] The international team of astronomers in this study consists of C. M. Carollo (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), T. J. Bschorr (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), A. Renzini (Padova Observatory, Italy), S. J. Lilly (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), P. Capak (Spitzer Science Center, California Institute of Technology, USA), A. Cibinel (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), O. Ilbert (Laboratoire d’Astrophysique de Marseille, France), M. Onodera (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), N. Scoville (California Institute of Technology, USA), E. Cameron (Swiss Federal Institute of Technology [ETH Zurich], Switzerland), B. Mobasher (University of California, USA), D. Sanders (University of Hawaii, USA), Y. Taniguchi (Ehime University, Japan).

Contacts

Marcella Carollo
ETH Zurich
Zurich, Switzerland
Tel: +4144633 3725
Email: marcella@phys.ethz.ch
Alvio Renzini
INAF, Astronomical Observatory of Padova
Padova, Italy
Tel: 049 8293 503
Email: alvio.renzini@oapd.inaf.it
Peter Capak
California Institute of Technology
California, USA
Tel: +1-626-395-6422
Email: capak@astro.caltech.edu
Nicky Guttridge
ESA/Hubble
Garching, Germany
Tel: +49-89-3200-6855
Email: nguttrid@partner.eso.org

| ESA/Hubble Information Centre
Further information:
http://www.spacetelescope.org/news/heic1313/

More articles from Physics and Astronomy:

nachricht Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>