Did Old Galaxies Grow Up Quicker Than New Ones?

This image shows the Hubble Ultra Deep Field 2012, an improved version of the Hubble Ultra Deep Field image featuring additional observation time. The new data have revealed for the first time a population of distant galaxies at redshifts between 9 and 12, including the most distant object observed to date. These galaxies will require confirmation using spectroscopy by the forthcoming NASA/ESA/CSA James Webb Space Telescope before they are considered to be fully confirmed.

Did some of the oldest galaxies grow up quickly? That’s an intriguing possibility raised by a research team that found “mature” galaxies some 12 billion light years away, when the universe was less than 2 billion years old.

“Today the universe is old and filled with galaxies that have largely stopped forming stars, a sign of galactic maturity,” stated Caroline Straatman from the Netherlands’ Leiden University, a graduate student who led the research. “However, in the distant past, galaxies were still actively growing by consuming gas and turning it into stars. This means that mature galaxies are expected to be almost non-existent when the universe was still young.”

Using data from the Magellan Baade Telescope’s FourStar Galaxy Evolution Survey and combining with other observatories, researchers looked at the young universe using near infrared wavelengths and found 15 galaxies at an average of 12 billion light-years away. While the galaxies are faint using visual wavelengths, they were easy to spot in infrared — and hosted as many as 100 billion stars per galaxy, on average.

The Milky Way over the ESO 3.6-metre Telescope, a photo submitted via Your ESO Pictures Flickr Group.  Credit:  ESO/A. Santerne
The Milky Way over the ESO 3.6-metre Telescope, a photo submitted via Your ESO Pictures Flickr Group. Credit: ESO/A. Santerne

These galaxies each have a similar mass to the Milky Way, but stopped making stars when the universe was “only 12 percent of its current age”, researchers said. This implies that star-forming happened much more quickly in the past than right now, since the rate is estimated at several hundred times higher than what is observed in the Milky Way now.

It’s not clear what caused the rapid aging, but you can be sure researchers will look into this further. You can read the research in Astrophysical Journal Letters or in preprint version on Arxiv. Other databases used include Hubble’s Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and the Great Observatories Origins Deep Survey.

Source: Netherlands Research School for Astronomy

FourStar Service: Red Galaxy Cluster Hides In Plain Sight

[/caption]

Located some 10.5 billion light years away in the general direction of the constellation of Leo, the most distant cluster of red galaxies so far discovered has been hiding in plain sight… until now. Thanks to the advanced observing techniques of FourStar, a new and powerful near-infrared camera on the 6.5m Magellan Baade Telescope, we’re now able to peer beyond faint and into the realm of the faintest. It’s 30 galaxies packed like sardines in a tin and their formation is the earliest known “galaxy city” in the Universe!

“These are the first steps of accurately measuring the rate at which these large urban cities formed in a dark-matter-dominated universe,” says Texas A&M astronomer, Dr. Casey Papovich. “The rate at which they come together tests our understanding of how structures in the universe formed. The broader the timeline, the better our chances of being accurate. Instrumentation is key, and as it evolves, we’ll keep pushing the boundaries.”

Up until now, this galaxy conglomeration had remained undisclosed – despite thousand upon thousands of hours of survey images taken in their area. It is truly amazing that they were overlooked by the huge ground-based telescopes and space-based research instruments, including the Hubble Space Telescope. There was just no accurate distance estimations until the FourStar project came along. Headed by Eric Persson of the Carnegie Observatories, the stellar team includes Carnegie’s David Murphy, Andy Monson, Dan Kelson, Pat McCarthy, and Ryan Quadri – a group whose findings will be published in the Astrophysical Journal Letters.

Just what is FourStar? It’s a specialized camera set with a group of five very specific filters which are sensitively tuned to a very narrow portion of the near-infrared spectrum. “These new filters are a novel approach; it’s a bit like being able to do a CAT scan of the sky to rapidly make a 3-D picture of the early universe,” says Swinburne’s Karl Glazebrook, who is leading the Australian component of the international collaboration formed in 2009.What sets it apart is its ability to accurately measure distances between Earth and target galaxies one at a time. This allows the program to build an incredible three-dimensional look at the source point.

“Most other surveys were just looking at the tip of the iceberg,” Dr. Kim-Vy Tran explains. “The modern technology contained in this camera enabled us to detect the faintest light possible, allowing us to see much more of the iceberg than previously revealed. It’s like we’re using a comb to sift through the very distant universe. The combination of filters and depth provided by this camera give us the equivalent of more teeth, resulting in better measurements and more accurate results.”

The survey was built one deep over an 11×11 arcminute field each in COSMOS, CDFS and UDS. When it comes to galaxy properties, they are looking at 1-2% accurate redshifts and the current 3-D map is looking back to when the Universe was only 3 billion years old.

“This means the galaxy cluster is still young and should continue to grow into an extremely dense structure possibly containing thousands of galaxies,” explained lead author Lee Spitler of Australia’s Swinburne University of Technology.

The FourStar Galaxy Evolution Survey (“Z-FOURGE”) is just the beginning. Through studies of clusters like this one, astronomers can and will get a better understanding of how galaxy clusters evolve in relationship to their environments and – possibly – how they assemble into larger structures. The survey, led by Dr. Ivo Labbé, a former Carnegie postdoctoral fellow, now at Leiden Observatory in the Netherlands, will also strengthen our abilities to determine distances. In just a half a year, the team “has obtained accurate distances for faint galaxies over a region roughly one-fifth the apparent size of the Moon” locating about another thousand galaxies at even further extents.

“The excellent image quality and sensitivity of Magellan and FourStar really make the difference,” Labbé said. “We look forward to many more exciting and unexpected discoveries!”

Original Story Source: Carnegie Science News Release.