Monday, March 27, 2023

3931 - GALAXIES - oldest and farthest?

 

-   3931 -    GALAXIES  -  oldest and farthest?   Astronomers pin down the age of the most distant galaxy seen 367 Million years after the Big Bang.  The James Webb Space Telescope (JWST) was built to peer back in time and identify the Universe’s very first galaxies.


------------  3931  -  GALAXIES  -  oldest and farthest?

-    Those James Webb 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

-

-    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.

-

-    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.

-

-   Astronomers set out decades ago to build the JWST with these findings in mind. But there’s a problem: our theories and models of galaxy formation suggest there shouldn’t be so many of these earliest galaxies. The JWST’s findings needed to be confirmed.

-

-   A team of researchers used the ESO’s ALMA (Atacama Large Millimetre/sub-millimetre Array) to examine a candidate galaxy from GLASS and to try to confirm it. Their paper is titled “Deep ALMA redshift search of a z = 12 , GLASS-JWST galaxy candidate”.

-

-    If all of these ultra-distant galaxy candidates were real, we’d have too many of them too early, forcing us to rethink how galaxies begin forming within the Universe.  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.

-

-   A 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 travelling for over 13.184 billion years and has traveled a distance of at least 26.596 billion light-years.

-

-   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. The astronomers turned to ALMA, the world’s most expensive ground-based telescope currently operating.

-

-    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.

-

-   Stars can generate oxygen on a short 50 Myr 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, and is likely the brightest emission line in the early Universe. Could ALMA find it?

-

-   Hubble Space Telescope’s Deep Field revealed thousands of galaxies in a seemingly empty spot in the sky. Now, the James Webb Space Telescope has taken deep field observations to the next level with its COSMOS-Web survey, revealing 25,000 galaxies in just six pictures, the first from this new survey. 

-

-    The first images to be released from the survey accounts for just 4% of the data that will eventually be collected with COSMOS-Web. The images show many types of galaxies, including spiral galaxies, examples of gravitational lensing, and evidence of galaxy mergers.

-

-    JWST’s first year and the goal of the survey is to map the earliest structures of the universe, as well as create a deep survey of up to 1 million galaxies. With a total of 255 hours of observing time, COSMOS-Web will map 0.6 square degrees of the sky with NIRCam, roughly the size of three full moons, and 0.2 square degrees with MIRI.

-

-     While the Hubble Deep Field imagers were stunning, these new images from JWST contain details that are inaccessible to Hubble.  Basically, everywhere ever we look, it’s a Deep Field. These engineering images are as sharp and crisp as images that Hubble can take, but at a wavelength of light that Hubble can’t see.

-

-    The goal of COSMOS-Web is to map the earliest structures of the universe and create a wide and deep survey of up to 1 million galaxies. The survey hopes to map cosmic reionization, study galaxy evolution and determine if dark matter can be linked to visible matter.

-

-   Over the course of 255 hours of observing time, COSMOS-Web will map 0.6 square degrees of the sky with NIRCam, roughly the size of three full moons, and 0.2 square degrees with MIRI.  (as of March, 2023)

-

-    This first snapshot of COSMOS-Web contains about 25,000 galaxies—an astonishing number larger than even what sits in the Hubble Ultra Deep Field.    It’s one of the largest JWST images taken so far. And yet it’s just 4 percent of the data we will get for the full survey.

-

-    The first epoch of COSMOS-Web MIRI observations obtained on January 6, 2023.   What were thought to be compact objects based on the best images we had so far, the JWST observations are now able to resolve these objects into multiple components, and in some cases even reveal the complex morphology of these extragalactic sources.

-

-    With these first observations, we have just barely scratched the surface of what is to come with the completion of this program, next year.”

-

                   March 26, 2023         GALAXIES  -  oldest and farthest?         3931                                                                                                                        

----------------------------------------------------------------------------------------

-----  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Monday, March 27, 2023  ---------------------------

 

 

 

 

         

 

-

 

 

 

 

           

 

 

No comments:

Post a Comment