Distant Galaxies
MPIA has an active galaxies and cosmology group. The main goal of this group is to empirically derive a picture of the evolution of the structural properties of galaxies, and to understand where, when and how the stars in galaxies were built up over cosmic time. These, in turn, are important tests of models of galaxy formation and evolution, guiding their development and refinement. |
Key science questions include the following.
- How goes galaxy size change with cosmic time? Do galaxies grow inside-out?
- When was the bulk of stellar mass formed? In what kind of galaxies was it formed, and where do the stars end up today?
- What is the rate of galaxy interactions throughout cosmic history?
- What is the interplay between galaxies and their massive central black holes?
A common thread connecting all of these themes is the requirement that one links the properties of distant galaxy populations in the early Universe with present-day galaxies, using similar data analysis and techniques. |
 |
|
 |
Using GEMS and FIRES,
astronomers at MPIA
(Barden / Trujillo / Haeussler / Rix, et al) and from around the world
have demonstrated for the first time that the relationship between a
galaxy's mass in stars and its size remains largely unchanged over the last 11
billion years. This has important implications for theories of galaxy
formation and evolution, requiring that galaxies form `inside-out'. More... |
|
Using COMBO-17, astronomers at MPIA (Borch / Meisenheimer / Bell / Rix) and at a number of institutions around the world have explored the evolution of the stellar mass content of the Universe over the last eight billion years. Roughly 1/2 of all stellar mass has formed since redshift one. The star formation is primarily in blue disk galaxies.
It would be expected then that most of the build-up of stellar mass since z = 1 would be in blue galaxies: it is not. Rather, the mass of the non-star-forming red galaxies has substantially increased in this time – there are physical processes which are turning off star formation on galaxy-wide scales, transforming the blue star-forming galaxies into 'old, red and dead' non-star-forming galaxies. More... |
 |
|
 |
- It appears as if the bulk of star formation at z ~0.7 (6 billion years ago) is not driven by galaxy merging; rather, most star formation occurs in disk galaxies.
More: a UV perspective...
More: an IR perspective...
- The rate of major galaxy mergers between massive galaxies is reasonably low. It is unlikely that all non-star-forming galaxies could be formed through major galaxy mergers. Other physical processes share responsibility for the transformation of star-forming into non-star-forming galaxies. More...
- In contrast, the frequency of galaxy mergers between already-formed non-star-forming galaxies may be rather high (see the image for an example - the spiral galaxy is in the background): while galaxy mergers may not create the bulk of non-star-forming galaxies, it may strongly shape the properties of at least the most massive ones. More...
|
Galaxy merging may be an important driver of galaxy evolution during the last eight billion years: it has been proposed that it may drive the bulk of star formation at z ~1, and merging has been proposed as one of the main drivers of the transformation of blue star-forming disks into red elliptical galaxies. Using GEMS and COMBO-17, astronomers at MPIA (Bell / Somerville / Meisenheimer et al) have explored the frequency and effect of galaxy merging during the last eight billion years.
|
|
In the present day Universe, there is a strong correlation between the mass of a galaxy's bulge and the mass of the supermassive black hole in its center. Astronomers at MPIA (Haering / Rix / Jahnke / Meisenheimer et al) have been studying the relationship between supermassive black holes and their host galaxies in order to gain insight into this surprising correlation.
- The scatter in the bulge mass-black hole mass correlation is less than a factor of two at the present day: such a tight correlation places important constraints on models wishing to reproduce this correlation. More...
- Many quasars (actively accreting supermassive black holes) at 0.5 < z < 1 (5-8 billion years ago) are hosted in galaxies with both a massive bulge component and signs of recent galaxy interactions and ongoing star formation: supermassive black hole accretion is unlikely in systems without both a a massive black hole and an abundant gas supply. More...
- The normalization of the black hole mass-bulge mass correlation is substantially higher at early times: black holes are more than 4 times more massive at z >1.7 and ~1.5 times higher at z ~1 than they are at the present, for a given bulge mass. A significant growth of the stellar body of a galaxy, without large amounts of growth of the supermassive black hole, is required to reach the present day black hole mass-bulge mass correlation. It may prove a challenge to current models to accomodate such evolution without violating the scatter of the present-day correlation. More...
|
 |
Verantwortlich / Responsible: Eric Bell
Letzte Änderung / Last update: September 26th |
