Subscribe free to our newsletters via your
. 24/7 Space News .




STELLAR CHEMISTRY
Multiple Mergers Generate Ultraluminous Infrared Galaxy
by Staff Writers
Tokyo, Australia (SPX) Jun 27, 2012


Image from the Subaru Prime Focus Camera (Suprime-Cam). Huge, complex tidal remnants surround Arp 220. (Credit: Ehime University / NAOJ). More images and captions.

A team of astronomers led by Professor Yoshiaki Taniguchi (Ehime University) has concluded that the ultraluminous infrared galaxy (ULIRG) Arp 220 (Figure 1) developed from a multiple merger among four or more galaxies.

Their new imaging data from the Subaru Telescope and optical spectroscopy from the W. M. Keck Observatory revealed two tidal tails that facilitated their analysis of Arp 220's development. Because Arp 220 is an archetypal or representative ULIRG, the team's findings facilitate an understanding of ULIRG development in general.

First discovered from the Infrared Astronomical Satellite's (IRAS) all-sky survey in the mid-1980s, ULIRGs are the most luminous class of galaxies in the relatively near or local Universe. Most of their energy output is in the infrared, suggesting that they contain a large amount of dust, an indication of immense star formation.

Astronomers have proposed different scenarios for the development of ULIRGs. Since ULIRGs' huge infrared luminosities (1012 Lsun), powered mostly by a large number of massive stars, are comparable to the high luminosity of quasars, the brightest class of active galactic nuclei, a 1988 scenario (Note 1) proposed that ULIRGs were an intermediate phase in the evolution of quasars after a merger.

Another scenario proposed by Professor Taniguchi and his associate in 1998 (Note 2) hypothesized that multiple mergers among several galaxies explained the observational properties.

However, a number of questions remained unanswered: 1) How many galaxies were merged into one? and 2) Which types of galaxies were merged into one? Since then, explanations for the origins of ULIRGs have remained controversial. The current team conducted research to help answer these questions and to propose a plausible, data-based explanation for the origin of ULIRGs.

The team made detailed optical imaging observations of Arp 220 using FOCAS (Faint Object Camera and Spectrograph) on the Subaru Telescope and the LRIS (Low Resolution Imaging Spectometer) on the Keck II Telescope. The new imaging data revealed a spectacular pair of tidal tails extending more than 50,000 light years.

Intermediate-mass stars (with masses a few to several times that of the Sun), the remains of intense star formation events called "starbursts", dominate the composition of the tidal tails.

The presence of an Ha absorption line (Figure 2) led to the first detection of these features. Dr. Kazuya Matsubayashi said, "I was very surprised when I found these Ha absorption features in the two tidal tails."

What could explain these surprising features? A merger between two galaxies is necessary to cause a starburst in a merging system. Therefore, two post-starburst galaxies could have produced the two long tidal tails.

However, four galaxies are needed to generate the two post-starburst galaxies (Figure 3). The post-starburst tidal tails revealed by the new observations suggest a new scenario for the merging history in Arp 220.

The team suggests that the two observed tidal tails in Arp 220 need a merger between two advanced (i.e., post-starburst) merger remnants. In sum, four spiral galaxies are necessary to explain the observed post-starburst tidal tails in Arp 220.

They conclude that Arp 220 comes from a multiple merger that includes at least four galaxies, not from a typical merger. The team thinks that this conclusion about Arp 220 can be applied to other galaxy groups.

There are a significant number of compact groups of galaxies in the Universe that could lead to multiple mergers. Professor Taniguchi noted, "Some of such compact groups have already merged into one. They are the ULIRGs observed to date." Some galaxies are associated together in a single gravitationally-bound group, and they will inevitably merge into one galaxy within several billion years.

Although ULIRGs are thought to evolve into quasars and then into giant early-type galaxies, future considerations of the evolution of galaxies will need to take into account the impact of multiple mergers, not just major mergers between two galaxies.

Professor Taniguchi applied this principle to the fate of our Milky Way Galaxy: "Very recently, NASA announced that our Milky Way Galaxy will merge with the Andromeda Galaxy (M31) into a giant elliptical galaxy within several billion years. Please don't worry. That would only be a merger between two galaxies, so our Milky Way will not evolve into a ULIRG."

These results will be published in The Astrophysical Journal, Volume 753, July 10, 2012.

.


Related Links
Subaru Telescope
Stellar Chemistry, The Universe And All Within It






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





STELLAR CHEMISTRY
ALMA Reveals Constituent of a Galaxy at 12.4 Billion Light-Years Away
Kyoto, Japan (SPX) Jun 26, 2012
An international research team, led by Associate Professor Tohru Nagao from Kyoto University, and including researchers from Japan and Europe, has observed a "submillimeter galaxy" located about 12.4 billion light-years away using ALMA (Atacama Large Millimeter/submillimeter Array), and has successfully detected an emission line from nitrogen contained in that galaxy. Comparisons between t ... read more


STELLAR CHEMISTRY
ESA to catch laser beam from Moon mission

Researchers Estimate Ice Content of Crater at Moon's South Pole

Researchers find evidence of ice content at the moon's south pole

Nanoparticles found in moon glass bubbles explain weird lunar soil behaviour

STELLAR CHEMISTRY
Opportunity Drives a Little

NASA tweaks flight path of Mars mission

Extensive Water in Mars Interior

Orbiter Out of Precautionary 'Safe Mode'

STELLAR CHEMISTRY
XCOR and Excalibur Almaz sign MOU for suborbital training services

Complex Challenges Solved In Tech Meetings For Commercial Crew Program

Boeing Completes Key Reviews of Space Launch System

Two NASA Visualizations Selected for Computers Graphics Showcase

STELLAR CHEMISTRY
Experts respond to rumors about Shenzhou-9

Staying stimulated in space

China's Hu praises astronauts for space advance

Packing Up Tiangong

STELLAR CHEMISTRY
Astrium awarded two ATV evolution studies from ESA

New Space Station Crew Confirmed

Spacewalk to work on ISS scheduled

Did You Say 1.2 Billion Particles Per Month?

STELLAR CHEMISTRY
SpaceX's Merlin 1D Engine Achieves Full Mission Duration Firing

USAF officials announce milestone Atlas V launch

EVE Underflight Calibration Sounding Rocket Launch

ILS and AsiaSat Announce a New Contract for an ILS Proton Launch

STELLAR CHEMISTRY
Forgotten Star Cluster Useful For Solar Science And Search for Earth Like Planets

SciTechTalk: Quick, name the planets!

Where Are The Metal Worlds And Is The Answer Blowing In The Wind

Metal-poor stars are rich with small planets

STELLAR CHEMISTRY
Google rolls in tablet market with Nexus 7

Mercury mineral evolution

Zynga building hub for mobile gadget game play

Google ramps up competition in hot tablet market




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement