Recent Talks

This talk will address the preferred mass and time for galaxy formation, in dark-matter haloes similar to that of the Milky way but when the Universe was a few Gigayears old. It is proposed that this is due to the interplay between two mechanisms, first *supernova* feedback that removes gas from the galaxy, and second *hot gas* in the deep potential well of massive haloes that suppresses cold gas supply to the galaxy, the two being effective in galaxies of lower and higher masses respectively. Cosmological simulations reveal that the same mechanisms are responsible for a robust sequence of events were galaxies undergo a dramatic gaseous *compaction*, sometimes caused by mergers, into a compact star-forming “blue nugget”. This triggers inside-out *quenching* of star formation, which is maintained by a hot massive halo aided by black-hole feedback, leading to todays passive elliptical galaxies. The blue-nugget phase is responsible for drastic transitions in the main galaxy structural, kinematic and compositional properties. In particular, the growth of the *black hole* in the galaxy center, first suppressed by supernova feedback when below the critical mass, is boosted by the compaction event and keeps growing once the halo is massive enough to lock the supernova ejecta by its deep potential well and the hot halo. The compaction events also trigger the formation of extended rings in high-z massive galaxies. These events all occur near the same characteristic halo mass, giving rise to the highest efficiency of galaxy formation and black-hole growth at this magic mass and time.

Zoom link:  https://rediris.zoom.us/j/98813487304

Gnuastro is an official GNU package that is currently maintained at the IAC. It is a large collection of programs to enable easy, robust, fast and efficient data analysis directly on the command-line. For example it can perform arithmetic operations on image pixels or table columns/rows without having to write programs, visualize FITS images as JPG or PDF, convolve an image with a given kernel or matching of kernels, perform cosmological calculations, crop parts of large images (possibly in multiple files), manipulate FITS extensions and keywords, and perform statistical operations. In addition, it contains programs to make catalogs from detection maps, add noise, make mock profiles with a variety of radial functions using monte-carlo integration for their centers, match catalogs, and detect objects in an image among many other operations. Gnuastro is written to comply fully with the GNU coding standards and integrates well with all Unix-like operating systems. This enables astronomers to expect a fully familiar experience in the building, installing and command-line user interaction that they have seen in all the other GNU software that they use (core components in many Unix-like/POSIX operating systems). In this SMACK, we will introduce Gnuastro and demonstrate a selection of its commonly used features. Relevant links are as follows. Lecture-notes: in https://gitlab.com/makhlaghi/smack-talks-iac/-/blob/master/smack-3-gnuastro.md, Gnuastro's main webpage: https://www.gnu.org/s/gnuastro, Gnuastro documentation: https://www.gnu.org/s/gnuastro/manual, Gnuastro tutorials: https://www.gnu.org/s/gnuastro/manual/html_node/Tutorials.html

Zoom link https://rediris.zoom.us/j/94454701469

About half of the stars in our Galaxy are born in binary systems meaning that their evolution might be affected by the presence of a companion. Many aspects of binary interaction are still unknown so understanding the products that result from interacting systems is crucial to unravel the physical mechanisms involved. A prototypical example of such post-interaction binary systems in the low- and intermediate-mass regime are Barium (Ba) stars. Ba stars are main-sequence or giant stars which show an enhancement of chemical elements that should not yet be overabundant at these evolutionary stages. Currently, it is widely accepted that these chemicals were transferred from a more evolved companion during a phase of mass transfer and that this companion evolved into a cool white dwarf. Understanding the orbital properties of these systems, as well as the stellar properties of the Ba star and its polluter, is the key to the system’s interaction history.

In the last years, the synergy between Gaia data, of unprecedented quality, high-resolution spectroscopy, long-term radial-velocity monitoring programmes, and state-of-the-art stellar and binary evolution models has contributed to a better understanding of the properties of Ba stars and provided new observational constraints to theoretical studies. The new Hertzsprung-Russell diagrams of Ba stars allowed us to accurately determine their evolutionary status and their masses. Additionally, we have recently determined the orbital properties of many main-sequence Ba stars, much less studied until now than their giant counterparts, which led to a thorough comparison of the properties of the two samples. The comparison between the distributions of masses, periods and eccentricities that resulted from this analysis allowed us to investigate the evolution of Ba-star systems between these two phases. Our models show that a second stage of binary interaction, this time between the main-sequence Ba star and its white-dwarf companion, also takes place in some systems, affecting the distribution of orbits observed among Ba giants.

Zoom link:   https://rediris.zoom.us/j/96557655189

Using deep photometry SBFs have been traditionally used to determine galaxy distances. We have recentlycomputed SBF spectra of stellar populations at moderately high resolution,which are fully based on empirical stellar spectral libraries. We show that the SBF spectraprovide new means to perform the stellar population studies, which, so far, have been tackled on the basis of the mean properties. We find that theSBFs are able to unveil very metal-poor components at the one percent level, which are not possible to disentangle with the standard analysis. In massive Early-Type Galaxies suchmetal-poor components correspond to the first stages in their chemicalenrichment and, therefore, the SBFs provide stringent constrains on their formation.

https://rediris.zoom.us/j/92233220080

The shell (or command-line) is the most commonly used (for advanced operations) interface to Unix-like operating systems.
In this session we'll introduce some of the most commonly used command-line/shell features and how they may be used in a hypothetical research project, using real astronomical data sets.
The session plan (with a listing of used commands and short explanation) is available here: https://gitlab.com/makhlaghi/smack-talks-iac/-/blob/master/smack-2-shell.md

https://rediris.zoom.us/j/98301657954

In the rapidly changing world of exoplanets, a new class of planets has emerged recently: the so called Ultra-Hot Jupiters, which have no analogue in our own solar system. Characterised by their short orbits and proximity to their host star, these worlds receive thousands of times the Earth’s insolation and have effective temperatures above 2000 K, making them intriguing candidates to study the most extreme atmospheric environments. A notable feature of these high temperatures is that the transmission spectra of these planets are rich in atomic metal lines, which provide new probes into the chemistry and dynamics of their atmospheres. I will highlight what we have recently learned about Ultra-Hot Jupiter atmospheres and focus on what knowledge can be derived directly from ground-based observations via transmission spectroscopy.

Connect to the following zoom link if you want to ask questions to the speaker:

https://rediris.zoom.us/j/96593309648

Re-ionisation followed the dark ages when enough stars and galaxies had been formed that their ionising output was sufficient for the task. Population III stars and star-forming galaxies started the re-ionisation process by forming primordial bubbles of ionised gas. These bubbles grew, illuminated by galaxies with strong Lyman continuum, and merged, till the entire Universe became ionised. The epoch corresponding to red-shift 6.5 is especially interesting as we now know the Universe became re-ionised by redshift ~5.5-6. High-z Lyα emitters are perhaps the most important witnesses of the re-ionisation process. Indeed, at redshifts larger than 6, Lyα sources would be undetectable, unless they are located within sizeable bubbles of ionised gas. I will show that a proto-cluster of Lyα emitting galaxies, spectroscopically confirmed at redshift 6.5, is within one such large ionised super-bubble. The kinds of bubbles that through percolation completed the re-ionisation of the universe.

Zoom link  https://rediris.zoom.us/j/94401326592

Short Meetings on Astro Computing Knowledge (SMACK) are a series of talks, or more appropriately 'live demonstrations', presented in the Instituto de Astrofísica de Canarias (IAC), targeting graduate students and researchers.  The main aim of the talks is to demonstrate the use and benefits of basic software tools that are commonly required for astronomical research. These talks will be showcasted at IAC Talks and recorded for easy future reference by the community.

The 1st SMACK is a brief introduction to the linux shell and the basic tools that come with it. We'll assume no previous knowledge and include a brief history of the POSIX standard.

Multi-conjugate adaptive optics (MCAO) has been proved to obtain the high-resolution images with a large field of view in solar observation. In this talk, after briefly introducing the basic principle and the development status of solar MCAO, I will give the progress of MCAO research based on the 1-m New Vacuum solar Telescope (NVST) in China. A solar MCAO experiment system had been successfully developed in 2017, and the MCAO-corrected high-resolution sunspots images were acquired. After that, a new MCAO system is being developed as an a regularly operating instrument for scientific observations of the sun for the NVST.

Se retransmitirá en directo, mediante streaming, un seminario compuesto de charlas cortas impartidas por trabajadoras del Instituto de Astrofísica de Canarias de todas las áreas del centro.