A dusty haze around blue compact dwarf galaxies

May 07, 2002

The possible effects of dust on the optical appearance of galaxies have preoccupied astronomers ever since Edwin Hubble realised 70 years ago that our Milky Way is just one galaxy amongst many in the universe. Direct observations of dust are needed to understand how much starlight is being released into the universe, what its colour is, and, therefore, what sort of stars were being formed through history in galaxies like our own Milky Way.

The team of Max-Planck scientists tackled this issue by measuring the brightness of galaxies in the invisible infrared spectrum of light expected from the dust particles blocking the visible starlight. They pointed ESA's Infrared Space Observatory (ISO) at 63 spiral and dwarf galaxies in the nearby Virgo cluster, carefully chosen to be representative of the overall population of galaxies in the local universe. Making use of ISO's unprecedented sensitivity at very long infrared wavelengths, this work represents the first statistical "census" of the total infrared energy output from "normal" galaxies.

Unexpectedly large amounts of infrared emission were discovered from very cold dust particles in almost all the galaxies measured. An example is shown in the picture, where the infrared emission from the spiral galaxy NGC4178 is depicted as contours overlaid on an image of the optical light. Remarkably, the temperature of the cold dust measured in the Virgo galaxies was found to range down to just ten degrees above absolute zero (-263 degrees Centigrade). As a consequence, astronomers are having to revise upwards by a factor of typically 10 the weight of dust in these galaxies compared to previous measurements. The data also show that up to half the total energy output of stars in normal galaxies has been converted from visible optical into infrared photons, much more than previously suspected, necessitating an upwards revision in the total amount of emitted starlight.

But the biggest surprise was found by the so-called Blue Compact Dwarf galaxies in the Virgo cluster. These are so called because when viewed with an optical telescope they are smaller than a tenth of the size of our own galaxy, and dominated by newly born massive blue stars, each shining up to 10,000 times more brightly that the sun. It had previously been supposed that dust exposed to this intense light should be very warm. The ISO observations, however, revealed huge amounts of very cold dust, in fact the coldest found from all the observed galaxies in the Virgo cluster. The scientists propose that this dust is so cold because it surrounds the galaxy, far away from the stars. They believe that "the infrared eyes of ISO may be tracing a dusty mixture of intergalactic gas, which the galaxies are still accumulating, leading to their further evolution."
-end-
Original publications:

Tuffs, R.J., Popescu, C.C., Pierini, D., Völk, H.J., Hippelein, H., Leech, K., Metcalfe, L, Heinrichsen, I. & Xu, C.: "Far-Infrared Photometry of a Statistical Sample of Late-Type Virgo Cluster Galaxies" The Astrophysical Journal Supplement Series, vol. 139, p37-79, March 15th 2002.

Popescu, C.C., Tuffs, R.J., Völk, H.J., Pierini, D. & Madore, B.F.: "Cold Dust in Late-Type Virgo Cluster Galaxies" The Astrophysical Journal, vol 567, p221-236, March 1st 2002

Contact:

Dr. Richard Tuffs
Max-Planck-Institute for Nuclear Physics
Saupfercheckweg 1, D-69117 Heidelberg, Germany.
Phone: +49-6221-516344
Fax: +49-6221-516324
Email: Richard.Tuffs@mpi-hd.mpg.de

Prof. H.J. Völk
Max-Planck- Institute for Nuclear Physics
Saupfercheckweg 1, D-69117 Heidelberg, Germany.
Phone: +49-6221-516295
Fax: +49-6221-516549
Email: Heinrich.Voelk@mpi-hd.mpg.de

Max-Planck-Gesellschaft

Related Astronomers Articles from Brightsurf:

Astronomers are bulging with data
For the first time, over 250 million stars in our galaxy's bulge have been surveyed in near-ultraviolet, optical, and near-infrared light, opening the door for astronomers to reexamine key questions about the Milky Way's formation and history.

Astronomers capture a pulsar 'powering up'
A Monash-University-led collaboration has, for the first time, observed the full, 12-day process of material spiralling into a distant neutron star, triggering an X-ray outburst thousands of times brighter than our Sun.

Astronomers discover new class of cosmic explosions
Analysis of two cosmic explosions indicates to astronomers that the pair, along with a puzzling blast from 2018, constitute a new type of event, with similarities to some supernovae and gamma-ray bursts, but also with significant differences.

Astronomers discover planet that never was
What was thought to be an exoplanet in a nearby star system likely never existed in the first place, according to University of Arizona astronomers.

Canadian astronomers determine Earth's fingerprint
Two McGill University astronomers have assembled a 'fingerprint' for Earth, which could be used to identify a planet beyond our Solar System capable of supporting life.

Astronomers help wage war on cancer
Techniques developed by astronomers could help in the fight against breast and skin cancer.

Astronomers make history in a split second
In a world first, an Australian-led international team of astronomers has determined the precise location of a powerful one-off burst of cosmic radio waves.

Astronomers witness galaxy megamerger
Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of scientists has uncovered a startlingly dense concentration of 14 galaxies that are poised to merge, forming the core of what will eventually become a colossal galaxy cluster.

Astronomers discover a star that would not die
An international team of astronomers has made a bizarre discovery; a star that refuses to stop shining.

Astronomers spun up by galaxy-shape finding
For the first time astronomers have measured how a galaxy's spin affects its shape -- something scientists have tried to do for 90 years -- using a sample of 845 galaxies.

Read More: Astronomers News and Astronomers Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.