galactic evolution tagged posts

Over 13 billion years ago, the first galaxies in the universe formed. They were elliptical, with intermediate black holes (IMBHs) at their centers surrounded by a halo of stars, gas, and dust. Over time, these galaxies evolved by flattening out into disks with a large bulge in the middle. They were then drawn together by mutual gravitational attraction to form galaxy clusters, massive collections that comprise the large-scale cosmic structure. This force of attraction also led to mergers, where galaxies and their central black holes came together to create larger spiral galaxies with central supermassive black holes (SMBHs).

Stock image. A new study presents the first measurements of the changing strengths of oxygen emission lines from the present day and back to 12.5 billion years ago. Credit: © robert / Fotolia

A new study casts light on how young, hot stars ionize oxygen in the early universe and the effects on the evolution of galaxies through time. It presents the first measurements of the changing strengths of oxygen emission lines from the present day and back to 12.5 billion years ago. The strength of doubly ionized oxygen increases going back in time, while the strength of singly ionized oxygen increases up to 11 billion years ago and then decreases for the remaining 1 to 2 billion years.

The cause of the two different evolutions is due to the changing physical conditions inside star-forming galaxies...

Galaxy NGC 2337 in constellation Lynx Credit: ESA/Hubble & NASA

This galaxy, NGC 2337, resides 25 million light-years away in the constellation of Lynx. NGC 2337 is an irregular galaxy, ie —along with a quarter of all galaxies in the universe—lacks a distinct, regular appearance. The galaxy was discovered in 1877 by the French astronomer Édouard Stephan who, in the same year, discovered the galactic group Stephan’s Quintet (heic0910i).

Although irregular galaxies may never win a beauty prize when competing with their more symmetrical spiral and elliptical peers, astronomers consider them to be very important. Some irregular galaxies may have once fallen into one of the regular classes of the Hubble sequence, but were warped and deformed by a passing cosmic companion...