* Astronomy

Members Login
Post Info
TOPIC: Distant Galaxies


L

Posts: 109922
Date:
RE: Distant Galaxies
 
 


Some galaxies in the early universe grew up quickly

Some galaxies grew up in a hurry. Most of the galaxies that have been observed from the early days of the universe were young and actively forming stars. Now, an international team of astronomers, including Carnegie's Eric Persson and Andy Monson, have discovered galaxies that were already mature and massive in the early days. Fifteen mature galaxies were found at a record-breaking average distance of 12 billion light years, when the universe was just 1.6 billion years old. Their existence at such an early time raises new questions about what forced them to grow up so quickly. The finding is published by The Astrophysical Journal Letters.
Read more



__________________


L

Posts: 109922
Date:
Quasar host galaxies
 
 


Title: Quasar host galaxies in the SDSS Stripe 82
Authors: Jari Kotilainen. Renato Falomo, Daniela Bettoni, Kalle Karhunen, Michela Uslenghi

We present first results from our study of the properties of ~400 low redshift (z < 0.5) quasars, based on a large homogeneous dataset derived from the Stripe 82 area of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). For this sky region, deep (r~22.4) u,g,r,i,z images are available, up to ~2 mag deeper than standard SDSS images, allowing us to study both the host galaxies and the Mpc-scale environments of the quasars. This sample greatly outnumbers previous studies of low redshift quasar hosts, from the ground or from space. Here we report the preliminary results for the quasar host galaxies. We are able to resolve the host galaxy in ~80 % of the quasars. The quasar hosts are luminous and large, the majority of them in the range between M*-1 and M*-2, and with ~10 kpc galaxy scale-lengths. Almost half of the host galaxies are best fit with an exponential disk, while the rest are spheroid-dominated. There is a reasonable relation between the central black hole mass and the host galaxy luminosity.

Read more (866kb, PDF)



__________________


L

Posts: 109922
Date:
RE: Distant Galaxies
 
 


Astronomers find most distant galaxy to date

With the help of NASAs Hubble and Spitzer Space Telescopes, a team of astronomers led by Hopkins Wei Zheng has discovered the most distant - and, hence, the youngest - galaxy ever observed with high confidence.
The telescopes captured light from that galaxy when the universe, now 13.7 billion years old, was just 500 million years of age. The light travelled about 13.2 billion light years before reaching the telescopes.

Read more



__________________


L

Posts: 109922
Date:
 
 

Seeing the Birth of the Universe in an Atom of Hydrogen

An international team of scientists led by researchers at Tel Aviv University have developed a method for detecting galaxies of stars that formed when the universe was in its infancy, during the first 180 million years of its existence. The method is able to observe stars that were previously believed too old to find, says Prof. Rennan Barkana of TAU's School of Physics and Astronomy.
Published in the journal Nature, the researchers' method uses radio telescopes to seek out radio waves emitted by hydrogen atoms, which were abundant in the early days of the universe. Emitting waves measuring about eight inches (21 centimetres) long, the atoms reflect the radiation of the stars, making their emission detectable by radio telescopes, explains Prof. Barkana. This development opens the way to learning more about the universe's oldest galaxies.

Read more



__________________


L

Posts: 109922
Date:
 
 

Title: Stars throw their weight in old galaxies
Authors: Nate Bastian

The observation that old, massive galaxies have a larger fraction of low-mass stars than their younger, lower-mass counterparts adds to mounting evidence that star formation may have been different in the early Universe.

Read more (4471kb, PDF)



__________________


L

Posts: 109922
Date:
 
 

Under 'dark halo' old galaxies have many more stars

Some of the oldest galaxies in the Universe have three times more stellar mass, and so many more stars, than all current models of galaxy evolution predict. The finding comes from the Atlas3D international team, led by Michele Cappellari (Oxford), and including ASTRON astronomers Paolo Serra, Raffaella Morganti and Tom Oosterloo, who found a way to remove the 'halo' of dark matter that has clouded previous calculations.
The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised. It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast. A report of the research is published in this week's Nature.

Read more


Under 'dark halo' old galaxies have many more stars

Read more



__________________


L

Posts: 109922
Date:
 
 

VLT Observations of Gamma-ray Burst Reveal Surprising Ingredients of Early Galaxies

An international team of astronomers has used the brief but brilliant light of a distant gamma-ray burst as a probe to study the make-up of very distant galaxies. Surprisingly the new observations, made with ESOs Very Large Telescope, have revealed two galaxies in the young Universe that are richer in the heavier chemical elements than the Sun. The two galaxies may be in the process of merging. Such events in the early Universe will drive the formation of many new stars and may be the trigger for gamma-ray bursts.
Read more



__________________


L

Posts: 109922
Date:
 
 

NASA's Spitzer Finds Distant Galaxies Grazed on Gas

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.
Astronomers have discovered that galaxies in the distant, early universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

Read more



__________________


L

Posts: 109922
Date:
 
 

NASA's Spitzer Finds Distant Galaxies Grazed on Gas

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.
Astronomers have discovered that galaxies in the distant, early universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

Read more



__________________


L

Posts: 109922
Date:
H-ATLAS J090311.6+003906
 
 


Title: Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS
Authors: Ivan Valtchanov, J. Virdee, R. J. Ivison, B. Swinyard, P. van der Werf, D. Rigopoulou, E. da Cunha, R. Lupu, D. J. Benford, D. Riechers, Ian Smail, M. Jarvis, C. Pearson, H. Gomez, R. Hopwood, B. Altieri, M. Birkinshaw, D. Coia, L. Conversi, A. Cooray, G. De Zotti, L. Dunne, D. Frayer, L. Leeuw, A. Marston, M. Negrello, M. Sanchez Portal, D. Scott, M. A. Thompson, M. Vaccari, M. Baes, D. Clements, M. J. Michalowski, H. Dannerbauer, S. Serjeant, R. Auld, S. Buttiglione, A. Cava, A. Dariush, S. Dye, S. Eales, J. Fritz, E. Ibar, S. Maddox, E. Pascale, M. Pohlen, E. Rigby, G. Rodighiero, D. J. B. Smith, P. Temi, J. Carpenter, A. Bolatto, M. Gurwell

We present Herschel-SPIRE Fourier Transform Spectrometer (FTS) and radio follow-up observations of two Herschel-ATLAS (H-ATLAS) detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81) we detect [OIII] 88\mum and [CII] 158\mum lines at a signal-to-noise ratio of ~5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0-005343 (SDP.130). Currently SDP.81 is the faintest sub-mm galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200-600 \mum wavelength range. The derived redshift of SDP.81 from the two detections is z=3.043 ±0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [OIII] 88\mum line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photo-dissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ~ 2000 cm^{-3} and the far-UV ionising radiation field G_0 ~ 200 (in units of the Habing field -- the local Galactic interstellar radiation field of 1.6x10^{-6} W/m^2). Using the CO derived molecular mass and the PDR properties we estimate the effective radius of the emitting region to be 500-700 pc. These characteristics are typical for star-forming, high redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local FIR/radio correlation, which hints that some fraction of the radio emission is coming from an AGN. The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33%. These indications, together with the high [OIII]/FIR ratio and the upper limit of [OI] 63\mum/[CII] 158\mum suggest that some fraction of the ionising radiation is likely to originate from an AGN.

Read more  (432kb, PDF)



__________________
1 2 319  >  Last»  | Page of 19  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard