Stars form at record speeds in galaxies

When galaxies form, their stars form everywhere at the same time or just concentrate in the tiny central region? Recent measures taken by an international team of researchers at the Max Planck Institute of Astronomy provide the first concrete evidence to show how star-forming regions in young galaxies indeed very small, but extremely exciting, they produce stars at surprisingly fast speeds.

Galaxies, including the Milky Way, contain hundreds of billions of stars. How could such a great galaxy system be formed? Is the central region containing previous stars forming and growing with time? Or are stars forming at the same time throughout the galaxy? An international research group led by scientists at the Max Planck Institute of Astronomy has now come close to answering the questions above.

The researchers studied one of the farthest known galaxies, a quasar called J1148 + 5251. The light from this galaxy takes 12.8 billion years to reach Earth; in contrast astronomical observations show that it appeared 12.8 billion years ago , providing scientists with the first idea of ​​the early stages of galaxy formation, only stars of the explosion. Big Bang is less than 1 billion years old.

The resulting images give complete details for the first time to allow the determination of the size of the star-forming region at a very early stage. With this information, the researchers were able to conclude that at the beginning of the star-forming center of J1148 + 5251 at record speeds - any speed greater than that would be contradicting the laws of physics.

Fabian Walter of the Max Planck Institute of Astronomy and the lead author said: 'This galaxy's star-forming speed surprised us. Each year its central region produces new stars with a total mass greater than a thousand suns. Meanwhile, the rate of star formation of the Milky Way is only about one sun each year. '

Proceeding near the physical limit

We know that young galaxies can produce impressive amounts of new stars, but that joint activity is only part of the overall picture. If the size of the star-forming regions is unknown, it will not be possible to compare star formation in the galaxies through theoretical models or comparison with star-forming regions in our galaxy.

With a diameter of only 4000 light years (the diameter of the Milky Way galaxy is about 100,000 light-years), the star-forming core region of J1148 + 5251 is extremely productive. In fact, it has moved very close to the limit set by the laws of physics. Stars are formed when cosmic dust clouds dissipate under its own gravity. When the clouds disintegrate, the temperature rises and the internal pressure begins to increase. Once the pressure reaches a certain level, all disintegration processes will stop and no more stars will be born. This is the upper limit on how many stars form in a given space over a given period of time.

The level of star formation in the Orion-KL region (rectangular) in the Orion nebula is equivalent to the central region of J1148 + 5251 but is limited to much smaller spaces. (Photo: NASA, ESA, Robberto (STScI / ESA), Project Group Orion Treasury)

Notably, the star-forming core of J1148 + 5251 has reached this absolute limit. The maximum level of activity can be found in some parts of our galaxy but only to a much smaller extent. For example, there is an area in the Orion nebula that is very active.'But in J1148 + 5251, we face a hundred million small regions combined.' Initial observations of different galaxies suggest that the upper limit specifies the number at one-tenth of the observed value at J1148 + 5251.

The growth from the inside

The compact star-forming region of J1148 + 5251 provides extremely interesting data for researchers in modeling the development of young galaxies. In this example, galaxies grow from the inside: in the early stages of star formation, there is a core region in which stars form very quickly. Perhaps such regions develop gradually over time, mainly as a result of collisions and intergalactic combinations that make up the star regions of larger mature galaxies.

The key to this result is a new measure: the first clear image of the region forming the central star of a distant quasar clearly shows the diameter of the region as well as its size. . This definite measure is itself a challenge. With a distance of nearly 13 billion light-years , the star-forming region with a diameter of 4,000 light-years is just like a euro viewed from a distance of 18 km (or the pound is observed 11 miles away).

However, one disadvantage is that observations are based only on electromagnetic radiation with a characteristic wavelength that is related to ionized carbon atoms. At this wavelength, the star-forming region of J1148 + 5251 still glows brightly though the center of the quasar is also extremely bright. Since the universe is expanding, radiation is converted in the direction of longer wavelengths when it returns to Earth , "docking" on our planet as radio waves with a wavelength of about 1 mm. But due to the normal nature of the wave, analyzing details at 1 mm wavelength is a thousand times more difficult than conventional light.

Observations at the required wavelength as well as the level of detail can only be carried out since 2006 by upgrading the IRAM interferometer - the combined radio telescope on the de Bure plateau in the Alps. , France.

Telescope of the future generation

The idea of ​​using specific ionized radiation to detect and produce images of star-forming regions of very distant astronomical objects was mentioned a long time ago. A combined radio telescope is currently under construction in northern Chile to serve as an observation program of ALMA based on this observation method. But it was not until Fabian Walter and his colleagues conducted the research that the above technique was carried out in practice. Walter said: 'The early stages of galactic evolution only started a billion years after the Big Bang. This will be the main research area in the coming years. Our research opens the door to star-forming regions in very young galaxies'.

Refer:
Walter et al.A kiloparsec-scale hyper-starburst in a quasar host less than 1 gigayear after the Big Bang.Nature, Feb 5, 2009;457 (7230): 699 DOI: 10.1038 / nature07681