Researchers at the Instituto de Astrofísica de Canarias (IAC) confirm the first detection of a relic galaxy with the Hubble Space Telescope. The results of this research are published today in Nature magazine.
There is a calculation suggesting that only one in a thousand massive galaxies is a relic of the early universe, conserving intact the properties it had when it was formed thousands of millions of years ago. For that reason when the researchers at the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), Michael Beasley and Ignacio Trujillo located this rarity they wrote a proposal for time on the Hubble Space Telescope to observe the globular clusters surrounding it, and so confirm what had been suggested by the observations they had made with ground-based telescopes.
Globular clusters are groups of stars which orbit round the outskirts of galaxies and they were formed with the galaxies at their birth. There are two types of populations of globular clusters: the red ones, which are born in massive galaxies, which are found nearer to their centres and have higher content of heavy elements than of Helium, and the blue ones, which have a lower fraction of metals and which are found around massive galaxies as a consequence of their absorbing smaller galaxies.
Analyzing these clusters helps provide information about the history of galaxies. The results of the research published today in Nature showed that the galaxy NGC 1277 has only the red globular cluster which formed along with it during the formation period. Since then it has remained unchanged. “Globular cluster systems are very sensitive to the history of galaxy formation” explains Michael Beasley, the first author of the article who also affirms that “this is the first time a galaxy so massive has been observed with so few blue globular clusters”.
The galaxy NGC 1277 is composed of a million million stars and its name comes from its entry in the historic New General Catalogue of Nebulae and Star Clusters. It is in the central zone of the Perseus Cluster, the biggest concentration of galaxies close to the Milky Way, and its relative proximity, 70 Mpc (225 million light years) makes it the ideal object for analyzing the properties of a galaxy which has remained essentially unchanged since the early days of the universe. “The galaxy NGC 1277 gives us a unique opportunity to study a “primitive” galaxy in the “local” universe” adds Ignacio Trujillo, another of the authors of the article.
When this galaxy was born it gave birth to 1,000 stars per year, whilst for comparison the Milky Way is currently forming only one star per year.
The reason why these researchers think that this massive galaxy has kept its original form and composition unchanged during all this time is because it formed as a satellite to the central galaxy of the Perseus cluster, which absorbed any material that could have fallen onto NGC 1277 and caused it to evolve differently. It orbits the central galaxy now, at a velocity of 1,000 kilometres per second.
The authors are planning to ask for more time with the Hubble Space Telescope and with its successor the James Webb Space Telescope, to observe the globular clusters of other relic galaxies.
Article: BEASLEY, Michael A. et al. “A single population of red globular clusters around the massive compact galaxy NGC 1277”, Nature. DOI: 10.1038/nature25756
auskier on June 11st, 2018 at 13:32 UTC »
If Hubble is still finding these amazing things across the universe, its almost impossible to think what the James Webb telescope will teach us in the coming decades.
_primecode on June 11st, 2018 at 12:13 UTC »
Extracted from NASA's article back in march:
mvea on June 11st, 2018 at 10:52 UTC »
The title of the post is a copy and paste from the title, subtitle and first paragraph of the linked academic press release here :
Journal Reference:
Michael A. Beasley, Ignacio Trujillo, Ryan Leaman, Mireia Montes.
A single population of red globular clusters around the massive compact galaxy NGC 1277.
Nature, 2018; 555 (7697): 483
DOI: 10.1038/nature25756
Link: https://www.nature.com/articles/nature25756
Abstract
Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes1,2,3,4. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites5,6,7,8,9,10. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies8,11,12. Here we report optical observations of the massive relic-galaxy candidate NGC 1277—a nearby, un-evolved example of a high-redshift ‘red nugget’ galaxy13,14,15,16,17. We find that the optical colour distribution of the cluster system of NGC 1277 is unimodal and entirely red. This finding is in strong contrast to other galaxies of similar and larger stellar mass, the cluster systems of which always exhibit (and are generally dominated by) blue clusters11. We argue that the colour distribution of the cluster system of NGC 1277 indicates that the galaxy has undergone little (if any) mass accretion after its initial collapse, and use simulations of possible merger histories to show that the stellar mass due to accretion is probably at most ten per cent of the total stellar mass of the galaxy. These results confirm that NGC 1277 is a genuine relic galaxy and demonstrate that blue clusters constitute an accreted population in present-day massive galaxies.