The candidate is so far away that it might even break our models of the early universe. But there's a catch.
By Jackson Ryan Former Science Editor at CNET.
Aug. 8, 2022 3:38 p.m.
A small portion of deep space observed by JWST. NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/Z. Levay
Astronomers armed with early data obtained by the James Webb Space Telescope (JWST) are hunting galaxies that existed just a few hundred million years after the Big Bang.
Rohan Naidu, an astrophysicist based at Harvard's and Smithsonian's jointly operated Center for Astrophysics, and his colleagues have been particularly good at uncovering these cosmic relics.
Just a few days after the JWST's first images were beamed across the planet in July, Naidu and his collaborators dropped a paper that reverberated across the web, picking up a real head of steam on social media. Using data from the 'scope, the researchers announced that they'd discovered a candidate for the most distant galaxy ever seen, dubbed GLASS-z13. Then, not even a week later, a number of groups found candidate galaxies ever farther away.
It's not surprising, then, that we have yet another candidate.
In a pre-print paper, released on Aug. 5 and yet to undergo peer review, Naidu and colleagues have detailed another distant galaxy candidate, from one of JWST's early release science programs, known as CEERS-1749. It's an extremely bright galaxy that, if confirmed, would have existed just 220 million years after the Big Bang -- and it could also rewrite our understanding of the cosmos.
But there's a huge catch.
CEERS-1749 could be one of the most distant galaxies we've ever seen. Or it could be lurking much closer to home. Essentially, the data seems to indicate two possible places for the galaxy to be -- and we won't know which one is correct without a lot more observation. That's earned it the title of "Schrodinger's galaxy candidate" in the paper submitted to pre-print repository, arXiv, on Aug. 4.
So, how can a galaxy like Schrodinger (the name we're running with because it's way more fun than CEERS-1749) seem to be in two different places? It's all about redshift.
To determine how far away a galaxy lies, astronomers study wavelengths of light. Specifically, they're interested in a phenomenon of light known as redshift. In a nutshell, light waves leaving distant galaxies get stretched over time, shifting the waves down the electromagnetic spectrum and making them more, well... red. So, ultraviolet light leaving a galaxy like Schrodinger won't reach Earth as ultraviolet light. Instead, it will be redshifted down into the infrared, which is great for us because that's just the kind of light JWST searches for.
And JWST has various filters, looking at distinct wavelengths of infrared. In examining a galaxy like Schrodinger, you can flick through the wavelengths like you might flick through a photo album. On the first few pages -- fewer red wavelengths -- you won't see a thing. Then, as you turn through and the wavelengths become more red, the ghost of a galaxy appears. In the most redshifted wavelengths, at the back of the album, the galaxy is a clearly defined object.
Redshift is denoted by the parameter z and higher z values mean a more distant object. One of the confirmed most-distant galaxies discovered to date, GN-z11, has a z value of 11.09. In the case of Schrodinger, the research team state it could have a z value of around 17. That would mean this light is from a time some 13.6 billion years ago.
This would also mean we might need to rethink our models of how galaxies evolved in the earliest days of the universe -- galaxies from that long ago should not be this bright, at least according to the model we currently use to explain our cosmos.
But maybe we don't need to break physics just yet.
The team suggest there is good environmental evidence that Schrodinger's z value might be around 5, which would mean its light is about 12.5 billion years old. Other galaxies in the region around Schrodinger all lie at about this distance. It might even be that Schrodinger is a satellite galaxy of one of its more massive neighbors.
But wait, there's more! Another group of researchers also studied this exact same galaxy from the early release data, publishing their own results to arXiv on the same day. Jorge Zavala, an astrophysicist at ALMA Japan, and his team added to the JWST data with data from an Earth-based telescopes in the French Alps and Hawaii.
They came to the conclusion that Schrodinger might be an impostermasquerading as a high-redshift galaxy when it's actually a much closer, dusty galaxy undergoing rapid star formation.
The take-home message? Work on this perplexing galaxy candidate is incomplete. JWST has been able to study the intensity of the light emitted by Schrodinger, but we need more measurements. In particular, spectroscopy will allow astrophysicists to scrutinize its redshift more accurately. The only barrier now is time -- getting enough time on telescopes around the world to study Schrodinger and solve the puzzle.
Jackson Ryan was CNET's science editor, and a multiple award-winning one at that. Earlier, he'd been a scientist, but he realized he wasn't very happy sitting at a lab bench all day. Science writing, he realized, was the best job in the world -- it let him tell stories about space, the planet, climate change and the people working at the frontiers of human knowledge. He also owns a lot of ugly Christmas sweaters.
See: https://www.cnet.com/health/open-en...-health-insurance-ends-tomorrow-what-to-know/
Schrodinger’s Galaxy Candidate: Puzzlingly Luminous at z≈17, or Dusty/Quenched at z≈5?
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
[
Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
[
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
[
Leiden Observatory, Leiden University, NL-2300 RA Leiden, Netherlands
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, The Netherlands
[
Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Dipartimento di Fisica e Astronomia, Università di Bologna, via Gobetti 93/2, 40122 Bologna, Italy
[
Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
[
Institute for Computational Cosmology, Department of Physics, Durham University, Durham, DH1 3LE, UK
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
Institute for Computational & Data Sciences, The Pennsylvania State University, University Park, PA, USA
Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
[
GRAPPA, Anton Pannekoek Institute for Astronomy and Institute of High-Energy Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Departament d’Astronomia i Astrofìsica, Universitat de València, C. Dr. Moliner 50, E-46100 Burjassot, València, Spain
Unidad Asociada CSIC ”Grupo de Astrofísica Extragaláctica y Cosmología” (Instituto de Física de Cantabria - Universitat de València)
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Astronomical Observatory, Ghent University, Krijgslaan 281, Ghent, Belgium
[
Astronomy Department, Yale University, 52 Hillhouse Ave, New Haven, CT 06511, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
JWST’s first glimpse of the z>10 Universe has yielded a surprising abundance of luminous galaxy candidates. Here we present the most extreme of these systems: CEERS-1749. Based on 0.6−5μm photometry, this strikingly luminous (≈26 mag) galaxy appears to lie at z≈17. This would make it an MUV≈−22, M⋆≈5×109M⊙ system that formed a mere ∼220 Myrs after the Big Bang. The implied number density of this galaxy and its analogues challenges virtually every early galaxy evolution model that assumes ΛCDM cosmology. However, there is strong environmental evidence supporting a secondary redshift solution of z≈5: all three of the galaxy’s nearest neighbors at <2.5\arcsec have photometric redshifts of z≈5. Further, we show that CEERS-1749 may lie in a z≈5protocluster that is ≳5× overdense compared to the field.
Intense line emission at z≈5 from a quiescent galaxy harboring ionized gas, or from a dusty starburst, may provide satisfactory explanations for CEERS-1749’s photometry. The emission lines at z≈5 conspire to boost the >2μm photometry, producing an apparent blue slope as well as a strong break in the SED*. Such a perfectly disguised contaminant is possible only in a narrow redshift window (Δz≲0.1), implying that the permitted volume for such interlopers may not be a major concern for z>10searches, particularly when medium-bands are deployed. If CEERS-1749 is confirmed to lie at z≈5, it will be the highest-redshift quiescent galaxy, or one of the lowest mass dusty galaxies of the early Universe detected to-date (A5500≈1.2 mag, M⋆≈5×108M⊙).
Both redshift solutions of this intriguing galaxy hold the potential to challenge existing models of early galaxy evolution, making spectroscopic follow-up of this source critical.
See: https://www.arxiv-vanity.com/papers/2208.02794/
* SED Spectral Energy Distribution of galaxies is a complex function of the star formation history and geometrical arrangement of stars and gas in galaxies. The computation of the radiative transfer of stellar radiation through the dust distribution is time-consuming. This aspect becomes unacceptable in particular when dealing with the predictions by semi-analytical galaxy formation models populating cosmological volumes, to be then compared with multi-wavelength surveys. Mainly for this aim, we have implemented an artificial neural network (ANN) algorithm into the spectro-photometric and radiative transfer code GRASIL in order to compute the SED of galaxies in a short computing time. This allows to avoid the adoption of empirical templates that may have nothing to do with the mock galaxies output by models. The ANN has been implemented to compute the dust emission spectrum (the bottleneck of the computation), and separately for the star-forming molecular clouds (MC) and the diffuse dust (due to their different properties and dependencies). We have defined the input neurons effectively determining their emission, which means this implementation has a general applicability and is not linked to a particular galaxy formation model. We have trained the net for the disc and spherical geometries, and tested its performance to reproduce the SED of disc and starburst galaxies, as well as for a semi-analytical model for spheroidal galaxies. We have checked that for this model both the SEDs and the galaxy counts in the Herschel bands obtained with the ANN approximation are almost superimposed to the same quantities obtained with the full GRASIL. We conclude that this method appears robust and advantageous, and will present the application to a more complex SAM in another paper.
See: https://academic.oup.com/mnras/article/410/3/2043/964380?login=false
Spectral energy distribution (SED) of galaxies provides fundamental information on the related physical processes. However, the SED is significantly affected by the amount of dust in its interstellar and in the intervening medium. Dust is primarily produced by asymtotic branch stars* and Type II supernovae. In addition, the dust mass increases through the metal accretion, and the grain size changes by the collisions between the grains. The contribution of each process and the extinction depend on the size distribution. Therefore, the SED model should treat the evolution of the dust mass and size distribution. In spite of the importance of dust evolution, many previous SED models have not considered the evolution of the total mass and size distribution in a physically consistent manner.
Hartmann352
* Asymptotic branch stars are stars that are in their next stage after a star has left the Main Sequence Stars Phase of its life. To recap, the Main Sequence is when the star fuses hydrogen into helium at its core. The Sun, our local star, is currently in this phase and will continue to be so for another billion or so years.
Hertzsprung/Russell diagram of tghe branches associated with theMain Stellar Sequencestars. astrobites.org
The first stage is Red Giant Branch, where the star has a helium core surrounded by a hydrogen core, but it is not yet fusing helium at the core.
The next stage is Horizontal Branch, where helium has begun fusing. Asymptotic Branch Stars follow Horizontal Branch stars on the evolutionary path, but they do not reach the same point. They track the path of the Red Branch. Asymptotic refers to a curve that tracks another, but whilst it might come close to touching, it never does.
Asymptotic Stars are low mass (0.8 Solar Masses) to intermediate mass (8 Solar Masses) that are typified by having a dormant carbon or oxygen core surrounded by layers of hydrogen and helium fusing layers. Our Sun will eventually become an Asymptotic Branch Star. These are Red Giant Star where their size increases due to the outward pressure overcoming Gravity.
During its lifetime, the star will become a Mira, a class of Variable Star. Miras is named after the first of their class to be identified as such. The prototype star is Mira, also known as Omicron Ceti in the constellation of Cetus.
The final stage of the star's life will begin as it starts to lose its mass in stellar winds. It is on the final steps in becoming a Planetary Nebula with a White Dwarf Star at the centre. The nebula clouds will not last forever and will disperse to leave the White Dwarf star alone, the only evidence that a star existed.
After a very long time, the White Dwarf will stop glowing and become a Black Dwarf Star. The length of time it takes to become a Black Dwarf star is longer than the age of the Universe. Therefore, none are believed to exist currently. The Black Dwarf will eventually break down and disperse, leaving all and any sign that a star existed in the first place.
See: https://www.universeguide.com/fact/asymptoticbranchstars
By Jackson Ryan Former Science Editor at CNET.
Aug. 8, 2022 3:38 p.m.
A small portion of deep space observed by JWST. NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/Z. Levay
Astronomers armed with early data obtained by the James Webb Space Telescope (JWST) are hunting galaxies that existed just a few hundred million years after the Big Bang.
Rohan Naidu, an astrophysicist based at Harvard's and Smithsonian's jointly operated Center for Astrophysics, and his colleagues have been particularly good at uncovering these cosmic relics.
Just a few days after the JWST's first images were beamed across the planet in July, Naidu and his collaborators dropped a paper that reverberated across the web, picking up a real head of steam on social media. Using data from the 'scope, the researchers announced that they'd discovered a candidate for the most distant galaxy ever seen, dubbed GLASS-z13. Then, not even a week later, a number of groups found candidate galaxies ever farther away.
It's not surprising, then, that we have yet another candidate.
In a pre-print paper, released on Aug. 5 and yet to undergo peer review, Naidu and colleagues have detailed another distant galaxy candidate, from one of JWST's early release science programs, known as CEERS-1749. It's an extremely bright galaxy that, if confirmed, would have existed just 220 million years after the Big Bang -- and it could also rewrite our understanding of the cosmos.
But there's a huge catch.
CEERS-1749 could be one of the most distant galaxies we've ever seen. Or it could be lurking much closer to home. Essentially, the data seems to indicate two possible places for the galaxy to be -- and we won't know which one is correct without a lot more observation. That's earned it the title of "Schrodinger's galaxy candidate" in the paper submitted to pre-print repository, arXiv, on Aug. 4.
So, how can a galaxy like Schrodinger (the name we're running with because it's way more fun than CEERS-1749) seem to be in two different places? It's all about redshift.
To determine how far away a galaxy lies, astronomers study wavelengths of light. Specifically, they're interested in a phenomenon of light known as redshift. In a nutshell, light waves leaving distant galaxies get stretched over time, shifting the waves down the electromagnetic spectrum and making them more, well... red. So, ultraviolet light leaving a galaxy like Schrodinger won't reach Earth as ultraviolet light. Instead, it will be redshifted down into the infrared, which is great for us because that's just the kind of light JWST searches for.
And JWST has various filters, looking at distinct wavelengths of infrared. In examining a galaxy like Schrodinger, you can flick through the wavelengths like you might flick through a photo album. On the first few pages -- fewer red wavelengths -- you won't see a thing. Then, as you turn through and the wavelengths become more red, the ghost of a galaxy appears. In the most redshifted wavelengths, at the back of the album, the galaxy is a clearly defined object.
Redshift is denoted by the parameter z and higher z values mean a more distant object. One of the confirmed most-distant galaxies discovered to date, GN-z11, has a z value of 11.09. In the case of Schrodinger, the research team state it could have a z value of around 17. That would mean this light is from a time some 13.6 billion years ago.
This would also mean we might need to rethink our models of how galaxies evolved in the earliest days of the universe -- galaxies from that long ago should not be this bright, at least according to the model we currently use to explain our cosmos.
But maybe we don't need to break physics just yet.
The team suggest there is good environmental evidence that Schrodinger's z value might be around 5, which would mean its light is about 12.5 billion years old. Other galaxies in the region around Schrodinger all lie at about this distance. It might even be that Schrodinger is a satellite galaxy of one of its more massive neighbors.
But wait, there's more! Another group of researchers also studied this exact same galaxy from the early release data, publishing their own results to arXiv on the same day. Jorge Zavala, an astrophysicist at ALMA Japan, and his team added to the JWST data with data from an Earth-based telescopes in the French Alps and Hawaii.
They came to the conclusion that Schrodinger might be an impostermasquerading as a high-redshift galaxy when it's actually a much closer, dusty galaxy undergoing rapid star formation.
The take-home message? Work on this perplexing galaxy candidate is incomplete. JWST has been able to study the intensity of the light emitted by Schrodinger, but we need more measurements. In particular, spectroscopy will allow astrophysicists to scrutinize its redshift more accurately. The only barrier now is time -- getting enough time on telescopes around the world to study Schrodinger and solve the puzzle.
Jackson Ryan was CNET's science editor, and a multiple award-winning one at that. Earlier, he'd been a scientist, but he realized he wasn't very happy sitting at a lab bench all day. Science writing, he realized, was the best job in the world -- it let him tell stories about space, the planet, climate change and the people working at the frontiers of human knowledge. He also owns a lot of ugly Christmas sweaters.
See: https://www.cnet.com/health/open-en...-health-insurance-ends-tomorrow-what-to-know/
Schrodinger’s Galaxy Candidate: Puzzlingly Luminous at z≈17, or Dusty/Quenched at z≈5?
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
[
Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
[
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Center for Astrophysics
|
Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
[
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
[
Leiden Observatory, Leiden University, NL-2300 RA Leiden, Netherlands
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, The Netherlands
[
Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Dipartimento di Fisica e Astronomia, Università di Bologna, via Gobetti 93/2, 40122 Bologna, Italy
[
Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
[
Institute for Computational Cosmology, Department of Physics, Durham University, Durham, DH1 3LE, UK
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
Institute for Computational & Data Sciences, The Pennsylvania State University, University Park, PA, USA
Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
[
GRAPPA, Anton Pannekoek Institute for Astronomy and Institute of High-Energy Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Departament d’Astronomia i Astrofìsica, Universitat de València, C. Dr. Moliner 50, E-46100 Burjassot, València, Spain
Unidad Asociada CSIC ”Grupo de Astrofísica Extragaláctica y Cosmología” (Instituto de Física de Cantabria - Universitat de València)
[
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
[
Astronomical Observatory, Ghent University, Krijgslaan 281, Ghent, Belgium
[
Astronomy Department, Yale University, 52 Hillhouse Ave, New Haven, CT 06511, USA
[
Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
[
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, Jagtvej 128, København N, DK-2200, Denmark
JWST’s first glimpse of the z>10 Universe has yielded a surprising abundance of luminous galaxy candidates. Here we present the most extreme of these systems: CEERS-1749. Based on 0.6−5μm photometry, this strikingly luminous (≈26 mag) galaxy appears to lie at z≈17. This would make it an MUV≈−22, M⋆≈5×109M⊙ system that formed a mere ∼220 Myrs after the Big Bang. The implied number density of this galaxy and its analogues challenges virtually every early galaxy evolution model that assumes ΛCDM cosmology. However, there is strong environmental evidence supporting a secondary redshift solution of z≈5: all three of the galaxy’s nearest neighbors at <2.5\arcsec have photometric redshifts of z≈5. Further, we show that CEERS-1749 may lie in a z≈5protocluster that is ≳5× overdense compared to the field.
Intense line emission at z≈5 from a quiescent galaxy harboring ionized gas, or from a dusty starburst, may provide satisfactory explanations for CEERS-1749’s photometry. The emission lines at z≈5 conspire to boost the >2μm photometry, producing an apparent blue slope as well as a strong break in the SED*. Such a perfectly disguised contaminant is possible only in a narrow redshift window (Δz≲0.1), implying that the permitted volume for such interlopers may not be a major concern for z>10searches, particularly when medium-bands are deployed. If CEERS-1749 is confirmed to lie at z≈5, it will be the highest-redshift quiescent galaxy, or one of the lowest mass dusty galaxies of the early Universe detected to-date (A5500≈1.2 mag, M⋆≈5×108M⊙).
Both redshift solutions of this intriguing galaxy hold the potential to challenge existing models of early galaxy evolution, making spectroscopic follow-up of this source critical.
See: https://www.arxiv-vanity.com/papers/2208.02794/
* SED Spectral Energy Distribution of galaxies is a complex function of the star formation history and geometrical arrangement of stars and gas in galaxies. The computation of the radiative transfer of stellar radiation through the dust distribution is time-consuming. This aspect becomes unacceptable in particular when dealing with the predictions by semi-analytical galaxy formation models populating cosmological volumes, to be then compared with multi-wavelength surveys. Mainly for this aim, we have implemented an artificial neural network (ANN) algorithm into the spectro-photometric and radiative transfer code GRASIL in order to compute the SED of galaxies in a short computing time. This allows to avoid the adoption of empirical templates that may have nothing to do with the mock galaxies output by models. The ANN has been implemented to compute the dust emission spectrum (the bottleneck of the computation), and separately for the star-forming molecular clouds (MC) and the diffuse dust (due to their different properties and dependencies). We have defined the input neurons effectively determining their emission, which means this implementation has a general applicability and is not linked to a particular galaxy formation model. We have trained the net for the disc and spherical geometries, and tested its performance to reproduce the SED of disc and starburst galaxies, as well as for a semi-analytical model for spheroidal galaxies. We have checked that for this model both the SEDs and the galaxy counts in the Herschel bands obtained with the ANN approximation are almost superimposed to the same quantities obtained with the full GRASIL. We conclude that this method appears robust and advantageous, and will present the application to a more complex SAM in another paper.
See: https://academic.oup.com/mnras/article/410/3/2043/964380?login=false
Spectral energy distribution (SED) of galaxies provides fundamental information on the related physical processes. However, the SED is significantly affected by the amount of dust in its interstellar and in the intervening medium. Dust is primarily produced by asymtotic branch stars* and Type II supernovae. In addition, the dust mass increases through the metal accretion, and the grain size changes by the collisions between the grains. The contribution of each process and the extinction depend on the size distribution. Therefore, the SED model should treat the evolution of the dust mass and size distribution. In spite of the importance of dust evolution, many previous SED models have not considered the evolution of the total mass and size distribution in a physically consistent manner.
Hartmann352
* Asymptotic branch stars are stars that are in their next stage after a star has left the Main Sequence Stars Phase of its life. To recap, the Main Sequence is when the star fuses hydrogen into helium at its core. The Sun, our local star, is currently in this phase and will continue to be so for another billion or so years.
Hertzsprung/Russell diagram of tghe branches associated with theMain Stellar Sequencestars. astrobites.org
The first stage is Red Giant Branch, where the star has a helium core surrounded by a hydrogen core, but it is not yet fusing helium at the core.
The next stage is Horizontal Branch, where helium has begun fusing. Asymptotic Branch Stars follow Horizontal Branch stars on the evolutionary path, but they do not reach the same point. They track the path of the Red Branch. Asymptotic refers to a curve that tracks another, but whilst it might come close to touching, it never does.
Asymptotic Stars are low mass (0.8 Solar Masses) to intermediate mass (8 Solar Masses) that are typified by having a dormant carbon or oxygen core surrounded by layers of hydrogen and helium fusing layers. Our Sun will eventually become an Asymptotic Branch Star. These are Red Giant Star where their size increases due to the outward pressure overcoming Gravity.
During its lifetime, the star will become a Mira, a class of Variable Star. Miras is named after the first of their class to be identified as such. The prototype star is Mira, also known as Omicron Ceti in the constellation of Cetus.
The final stage of the star's life will begin as it starts to lose its mass in stellar winds. It is on the final steps in becoming a Planetary Nebula with a White Dwarf Star at the centre. The nebula clouds will not last forever and will disperse to leave the White Dwarf star alone, the only evidence that a star existed.
After a very long time, the White Dwarf will stop glowing and become a Black Dwarf Star. The length of time it takes to become a Black Dwarf star is longer than the age of the Universe. Therefore, none are believed to exist currently. The Black Dwarf will eventually break down and disperse, leaving all and any sign that a star existed in the first place.
See: https://www.universeguide.com/fact/asymptoticbranchstars
Facebook
Twitter
Instagram