Wednesday, February 15, 2023

3877 - GALAXY FORMATIONS - how are they born?

 

-  3877  -  GALAXY  FORMATIONS  -  how are they born?  -   The Multi-Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope was used to study existing stars in the galaxy. It can image the galaxy in one observation with multiple wavelengths of light. At the same time, it measures the intensity of light coming from various regions. In doing so, it provides a fascinating “3D” look at the galaxy and its components.


----------  3877  -   GALAXY  FORMATIONS  -  how are they born?

-    Galaxies fill a lot of roles in the universe. The most obvious one is star formation factories.  A galaxy classified as a late-type spiral means it turned gas into stars more slowly in the past and still has a lot left today.

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-    The galaxy has a massive collection of stars at its heart. In addition, it sports older star clusters. These all indicate starforming activity in the ancient past. There’s also ample evidence of more recent star-birth activity across the entire galaxy. Bright nebulae highlight places where newborn stars are forming.

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-  The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation instrument in development for ESO´s Very Large Telescope (VLT). MUSE is an extremely powerful and innovative 3D spectrograph with a wide field of view, providing simultaneous spectra of numerous adjacent regions in the sky. The instrument is fed by a new multiple-laser adaptive optics system on the VLT.

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-    The Atacama Large Millimeter Array provided a different view using millimeter waves (close to radio waves). It specifically observes the clouds of hydrogen in the galaxy. The idea is to compare the amount of gas available for star formation to the populations of stars already formed. By using two different instruments, astronomers get a better idea of what triggers star birth.

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-      The creation of supermassive stars can gobble up the available gas. That leaves very little to form smaller stars. In other places, the deaths of supermassive stars in supernova explosions send out shock waves. Those can trigger the process of star birth in nearby molecular clouds.

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-    Multiwavelength studies of galactic star formation to look at all aspects of a galaxy’s structure using as many different approaches in as many wavelengths as possible.

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-   Ultimately, studies of galaxies like NGC 4303 and others will give a detailed understanding of just how galaxies and their stars form and evolve. In the case of NGC 4303, the extent of both past and future star formation looks quite impressive. The almost uniform distribution of neutral gas clouds across its spiral arms and core predicts a very bright future for this galaxy

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-   Staring off into the ancient past with a $10 billion space telescope, hoping to find extraordinarily faint signals from the earliest galaxies, might seem like a forlorn task. But it’s only forlorn if we don’t find any. Now that the James Webb Space Telescope has found those signals, the exercise has moved from forlorn to hopeful.

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-     The James Webb Space Telescope (JWST) was built to peer back in time and identify the Universe’s very first galaxies. Those observations are meant to forge a link between the ancient galaxies and the galaxies we see now, including our own. That link will help astronomers understand how galaxies like ours formed and evolved over billions of years.

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-     The expansion of the Universe stretches the light emitted by ancient objects billions of years ago. The stretching shifts the light toward the red end of the visible light spectrum. The James Webb Space Telescope was built to see this light and identify the ancient galaxies that emitted it.

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-    The telescope’s GLASS Survey used the galaxy cluster called Pandora’s Cluster (Abell 2744) as a gravitational lens to magnify distant galaxies behind it and found 19 bright objects that appear to be early galaxies.

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-    The ESO’s ALMA (Atacama Large Millimetre/sub-millimetre Array) was used  to examine a candidate galaxy from GLASS.  There’s a tremendous difference between the light that a distant galaxy emits and the light that arrives at our eyes after journeying for billions of light-years across the Universe.

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-     Galaxy named GHZ2/GLASS-z12, one of the brightest and most robust candidates at z > 10, according to the JWST observations. z > 10 means that the light from the galaxy has been traveling for over 13.184 billion years and has traveled a distance of at least 26.596 billion light-years.

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-   Spectroscopy is needed to confirm the primeval nature of these candidates. It’s possible that the light from some of these galaxies is red due to dust rather than distance, and spectroscopy could help differentiate between the two.

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-    They used it to look for an oxygen line (O III) in the spectroscopy at the same frequency found in the JWST observations. O III is doubly-ionized oxygen, and it’s key because oxygen has a short formation time relative to other elements. Focusing on oxygen increased the likelihood of detection.

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-    Stars can generate oxygen on a short 50 Million year time scale. Other elements, like carbon, for example, take nearly 500 Myr to appear in a galaxy. This means that oxygen is generally the best redshift indicator.  Could ALMA find it?

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February 15, 2023       Galaxy  Formation                                       3877                                                                                                                        

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--------------------- ---  Wednesday, February 15, 2023  ---------------------------

 

 

 

 

         

 

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