From Manu Garcia at IAC: “Why is massive star formation quenched in galaxy centers?”


Manu Garcia, a friend from IAC.

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IAC

Instituto de Astrofísica de Canarias – IAC

27 November 2017.

Tags: Galaxies
Manu [Astrologus] Garcia

Contact:

Fatemeh Tabatabaei (English)
ftaba@iac.es

Almudena Prieto (Spanish/English)
aprieto@iac.es

1
NGC 1097.
Magnetic fields control the collapse of the molecular clouds in the nuclear ring of the galaxy NGC 1097. As a result, formation of massive stars is suppressed in zones of strong magnetic fields (contours). Credit: Gabriel Pérez, SMM (IAC).

A study whose first author is a researcher at the IAC and published today in Nature Astronomy points to the role of the magnetic field responsible for decelerating the rate of formation of this type of stars in the center of galaxies, and without which question the current model of the “Big Bang”.

The cosmological model we make reference to today to explain the universe, the model of the “Big Bang” is intended to describe all the phenomena we observe, including galaxies and their evolution from the earliest periods to the present day. One of the main problems facing is that predicts a rate of star formation born -Speed ​​the new star- too high, because at that pace all gas and galactic dust should have become stars when the universe was only a fraction of its current age, about 13,800 million years. More than half galaxies we see, mainly spirals, however are actively forming stars right now. This discordance between the theoretical prediction and observation has obliged to investigate more closely the processes that can slow the rate at which stars are born, processes known as “suppression of star formation.” Without them, the Big Bang model we take for valid fails.

Have proposed several mechanisms that could “turn off” star formation, for example, the “feedback” of supernovae in massive star clusters that “breaks” forming molecular clouds of stars, but it is still essential to measure and verify other possible processes . One of them, gathered in an article published today in the journal Nature Astronomy and whose first author is a researcher at the Institute of Astrophysics of the Canary Islands (IAC) Fatemeh Tabatabaei, pointing to magnetic fields as responsible for the stars formed more slowly.

To investigate in detail the parameters of star formation in the central region of the spiral galaxy NGC 1097, concluded that a relatively large magnetic field can slow the formation of new stars, as these fields “press” molecular clouds, slowing or stopping its tendency to collapse and create new stars. But the study results have been even more revealing because they have shown that this mechanism is happening around the center of NGC 1097. This could not have combined observations taken with Hubble (HST) in the visible Space Telescope with observations at radio with the Very Large Array (VLA) and submillimeter Array (SMA) to explore the effect of turbulence, and the magnetic stellar radiation for forming massive stars in the ring surrounding the core of the field galaxy.

NASA/ESA Hubble Telescope

NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

CfA Submillimeter Array Mauna Kea, Hawaii, USA,4,207 m (13,802 ft) above sea level

This ring contains a distinct areas where stars are forming within huge and complex molecular clouds. The main finding was obtained an inverse relationship between the rate of star formation in a given molecular cloud and its magnetic field: the larger the magnetic field, the slower the rate of star formation.

“To achieve this, we had to separate the magnetic field energy and other energy sources in the interstellar medium, which are thermal energy, and the general nonthermal but nonmagnetic” explains Fatemeh Tabatabaei. “Only by combining high-quality observations at different wavelengths we could do, and when we separate these energy sources the effect of the magnetic field was surprisingly clear.” In this sense, Almudena Prieto, also a researcher at the IAC and one of the authors of the research adds that “although I have been working in the central region of NGC 1097 in the optical and infrared for some time, only when we considered the magnetic field could realizing their relevance in decreasing the rate at which stars form. ”

The consequences of their findings are significant and shed light on several “astrophysical puzzles” interrelated. First, as the magnetic field does not allow very large molecular clouds collapse and form stars, they could only emerge after the first break up into smaller clouds. This would mean that the stars formed in these circumstances are smaller than in other parts of galaxies. The trend of very massive galaxies to accommodate smaller stars at their centers is a recent discovery and, in a way, still controversial, but reinforced by this research. It is also interesting that the presence of supermassive black holes in galactic nuclei tend to enhance the magnetic field around, so that the quenching mechanism must be more effective in these central areas thereof.

See the full article here.

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The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
The Centro de Astrofísica en La Palma (CALP)
The Observatorio del Teide (OT), in Izaña (Tenerife).
The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

The IAC’s research programme includes astrophysical research and technological development projects.

The IAC is also involved in researcher training, university teaching and outreachactivities.

The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.


Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC