Remote Colloquium: Fuyan Bian (Host: Kristian Finlator)
Apr 17 @ 3:00 pm – 4:00 pm
Remote Colloquium: Fuyan Bian (Host: Kristian Finlator) @ Online

Evolution of Ionized Interstellar Medium across Cosmic Time

Fuyan Bian, European Southern Observatory

The ionized interstellar medium (ISM) provides essential information on the star-forming environments, metal enrichment, and underlying ionizing radiation field in galaxies. It is crucial to understand how the ionized ISM evolves with Cosmic time. In this talk, I will present a sample of local galaxies that closely resemble the properties of high-redshift galaxies at high redshift. These local analogs of high-redshift galaxies provide a unique local laboratory to study high-redshift galaxies. I will discuss how to use these analogs to improve our understanding of the high-redshift metallicity empirical calibrations and physical mechanism(s) to drive the evolution of optical diagnostics lines from high redshift to low redshift.

Remote Cappuccino Talk: Valentina D’Odorico (Host: Kristian Finlator)
Apr 20 @ 9:00 am – 10:00 am
Remote Cappuccino Talk: Valentina D'Odorico (Host: Kristian Finlator) @ Online

The role if the intergalactic medium in the baryon cycle

Valentina D’Odorico, INAF Osservatorio Astronomico di Trieste

The intergalactic medium (IGM) plays a relevant role in galaxy evolution being the reservoir of gas for star formation and, at the same time, collecting the products of star formation ejected from galaxies. The IGM is studied mainly in absorption, in the spectra of high redshift bright objects. In this talk, I will briefly review the recent development in the study of the IGM, in particular the determination of its metal enrichment, in the context of the baryon cycle in galaxies. I will focus my presentation on the high redshift regime, reaching the epoch of reionization, where strong constraints are set to the models of galaxy evolution.

Remote Colloquium: Anders Johansen (Host: Wladimir Lyra)
Apr 24 @ 9:00 am – 10:00 am
Remote Colloquium: Anders Johansen (Host: Wladimir Lyra) @ Remote

Planet formation in protoplanetary discs around young stars

Anders Johansen (Lund University, Sweden)

Planets form in protoplanetary discs around young stars as dust and ice particles collide to form larger and larger bodies. I will present a coherent theory framework for the formation of planetary systems. Dust grows to pebbles by coagulation and deposition of volatile ices, but the continued growth to planetesimals is hampered by the poor sticking of mm-cm-sized pebbles. Planetesimals can nevertheless form by gravitational collapse of pebble clumps concentrated in the turbulent gas through the streaming instability. The subsequent growth initially occurs by planetesimal-planetesimal collisions, but the accretion rate of pebbles dominates the growth from 1000-km-sized protoplanets to form the solid cores of gas giants, ice giants and super-Earths. The high growth rates by pebble accretion allow planetary cores to start their growth in much more distant positions than their final orbits. The giant planets orbiting our Sun and other stars can therefore be formed in consistency with planetary migration.

Pizza Lunch (Virtual): Sultan Hassan
Apr 27 @ 12:30 pm – 1:30 pm
Pizza Lunch (Virtual): Sultan Hassan @ Online

Competing effects of the duty cycle and scatter around star formation during reionization as observed by JWST and SKA

Sultan Hassan, NMSU

PDS Atmospheres Node meeting
Apr 28 @ 2:00 pm – 3:00 pm
Pizza Lunch (Virtual): Kelly Sanderson
May 4 @ 12:30 pm – 1:30 pm
Pizza Lunch (Virtual): Kelly Sanderson @ Online

ASTR 598

Kelly Sanderson, NMSU

Sarah Kovac: Thesis Proposal
May 8 @ 3:00 pm – 4:00 pm
Sarah Kovac: Thesis Proposal @ Remote via Zoom

Enhancing Time-Dependent Solar Wind Models to Constrain Effects on Non-Magnetized Planetary Atmospherese

Sarah Kovac, NMSU

The Sun generates a solar wind of particles which propagate throughout the solar system and can be modeled using magnetohydrodynamics and in situ spacecraft data. This solar wind is known to interact with the ionospheres and upper atmospheres of terrestrial planets, thus contributing to their atmospheric evolution. Atmospheric stripping, the process of ionizing particles such that they escape the atmosphere of a planet, is an essential component in atmospheric evolution. One feature of the solar wind is a stream interaction region (SIR), which is created when multiple solar wind streams are compressed to create regions with higher densities, stronger magnetic fields, and steeper velocity profiles. The effects of high energy solar events, like coronal mass ejections and flares, have been shown to contribute to atmospheric stripping, but lower energy events, such as SIRs, have not been studied in detail. These lower energy events are far more common and present throughout the entire solar cycle. Thus, while less intense, SIRs provide an equally important, but poorly understood, source of planetary atmospheric erosion. Venus and Mars are ideal targets for studying atmospheric erosion via SIRs due to their lack of an intrinsic magnetic field, similar atmospheric compositions, sufficient orbital spacing (0.7 AU and 1.5 AU, respectively), and known auroral emission. Both the auroral emission intensity and altitude are dependent on the energy of the solar wind, meaning it can be used as a tracer for space weather conditions. Most current solar wind models primarily make use of steady-state solutions, which fail to account for evolution in the photosphere, and consequently the corona, over time. As such, the models may be producing solar wind measurements in the vicinity of Venus and Mars that are misleading. This work will utilize a new time-dependent solar wind model to capture solar wind and SIR evolution, providing constraints on the influence of SIRs on terrestrial planet atmospheres. Utilizing in situ data from multiple heliocentric distances, this work will improve the model’s ability to make accurate predictions and help determine conditions where the solar wind may be responsible for atmospheric emission. Hence, this research will improve the understanding of solar wind evolution throughout the inner solar system and allow us to accurately characterize the effects of solar wind variability on terrestrial planet atmospheres.
PDS Atmospheres Node meeting
May 12 @ 2:00 pm – 3:00 pm
No Colloquium – Final Exam Week
May 15 @ 3:15 pm – 4:15 pm
No Colloquium - Final Exam Week @ BX102

Colloquium Title

Colloquium Speaker Name, Affiliation

Abstract text

Remote Colloquium Thesis Defense: Drew Chojnowski
May 29 @ 2:30 pm – 3:30 pm
Remote Colloquium Thesis Defense: Drew Chojnowski @ Online

H-Band Spectroscopy of Exotic, Massive Stars

Drew Chojnowski, NMSU

We report on spectroscopy of exotic B-type emission line (Be) stars and chemically peculiar (CP) stars in the near-infrared (NIR) H-band, using data provided by the Apache Point Observatory Galactic Evolution Experiment, one of the sub-surveys of the Sloan Digital Sky Survey (SDSS). Between 2011-2020, SDSS/APOGEE has observed more than a million stars in the Milky Way Galaxy (MW), with roughly 10% of the targets being hot, blue stars that serve as telluric absorption standard stars (TSS). The TSS are selected mostly on the basis of having blue raw J-K color indices with no preference for any particular spectral type that might be known from optical spectroscopy. This targeting strategy has led to the TSS being a mixed bag, with those observed in the MW Halo typically being F-type stars that are only slightly more massive than the Sun, and with those observed in the MW Disk and Bulge being OBA-type stars of a few up to 20 times the mass of the Sun. While the vast majority of the TSS are superficially normal main sequence stars, the inclusion of large numbers of Be and CP stars has serendipitously resulted in the largest ever homogeneous spectroscopic surveys of these stellar classes, both of which present observational anomalies that remain very poorly understand despite more than a hundred years of research. Prior to SDSS/APOGEE, the H-band spectra of Be and CP stars had only been discussed in a handful of studies, all of which used small numbers of spectra of considerably lower resolution than the R=22,500 of the APOGEE instruments. The material presented in this thesis therefore represents the first ever detailed studies of Be and CP stars in the H-band, while also greatly expanding the known samples through discovery of many hundreds of new examples.