Colloquium Thesis Defense: Lauren Kahre
Jan 23 @ 3:00 pm – 4:00 pm
Colloquium Thesis Defense: Lauren Kahre

Extinction Mapping and Dust-to-Gas Ratios of Nearby Galaxies

Lauren Kahre, NMSU

We present a study of the dust{to{gas ratios in 31 nearby (D >
10 Mpc) galaxies. Using Hubble Space Telescope broad band WFC3/UVIS UV and
optical images from the Treasury program LEGUS (Legacy ExtraGalactic UV
Survey) combined with archival HST/ACS data, we correct thousands of
individual stars for extinction across these galaxies using an
isochrone-matching (reddening-free Q) method. We generate extinction maps
for each galaxy from the individual stellar extinctions using both
adaptive and fixed resolution techniques, and correlate these maps with
neutral HI and CO gas maps from literature, including The HI Nearby Galaxy
Survey (THINGS) and the HERA CO-Line ExtraGalactic Survey (HERACLES). We
calculate dust-to-gas ratios and investigate variations in the dust-to-gas
ratio with galaxy metallicity. We find a power law relationship between
dust-to-gas ratio and metallicity. The single power law is consistent with
other studies of dust-to-gas ratio compared to metallicity, while the
broken power law shows a significantly shallower slope for low metallicity
galaxies than previously observed. We find a change in the relation when
H_2 is not included. This implies that underestimation of N_H2 in
low-metallicity dwarfs from a too-low CO-to-H2 conversion factor X_CO
could have produced too low a slope in the derived relationship between
dust-to-gas ratio and metallicity. We also
compare our extinctions to those derived from fitting the spectral energy
distribution (SED) using the Bayesian Extinction and Stellar Tool (BEAST)
for NGC 7793 and and systematically lower extinctions from SED-fitting as
compared to isochrone matching. Finally, we compare our extinction maps of
NGC 628 to maps of the dust obtained via IR emission from Aniano et al.
(2012) and find a factor of 2 difference in dust-to-gas ratios determined
from the two maps, consistent with previous work.

Colloquium: Brian Svoboda (Host: Moire Prescott)
Sep 6 @ 3:15 pm – 4:15 pm
Colloquium: Brian Svoboda (Host: Moire Prescott) @ BX102

Starless clumps and the earliest phases of high-mass star formation in the Milky Way

Brian Svoboda, NRAO Jansky Fellow

High-mass stars are key to regulating the interstellar medium, star formation activity, and overall evolution of galaxies, but their formation remains an open problem in astrophysics. In order to understand the physical conditions during the earliest phases of high-mass star formation, I will present observational studies we have carried out on dense starless clump candidates (SCCs) that show no signatures of star formation activity. We identify 2223 SCCs from the 1.1 mm Bolocam Galactic Plane Survey, systematically analyse their physical properties, and show that the starless phase is not represented by a single timescale, but evolves more rapidly with increasing clump mass. To investigate the sub-structure in SCCs at high spatial resolution, we investigate the 12 most high-mass SCCs within 5 kpc using ALMA. We find previously undetected low-luminosity protostars in 11 out of 12 SCCs, fragmentation equal to the thermal Jeans length of the clump, and no starless cores exceeding 30 solar masses. While uncertainties remain concerning the star formation efficiency in this sample, these observational facts are consistent with models where high-mass stars form from initially low- to intermediate-mass protostars that accrete most of their mass from the surrounding clump. I will also present on-going research studying gas inflow signatures with GBT/Argus and ALMA, and the dense core mass function with the JVLA.

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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.

All Department meeting
Aug 21 @ 3:00 pm – 4:00 pm
All Department meeting @ Online

Department “all-hands” meeting

No Colloquium
Aug 28 @ 3:00 pm – 4:00 pm
No Colloquium @ BX102

Colloquium Title

Colloquium Speaker Name, Affiliation

Abstract text

Colloquium:Inclusive Astronomy
Sep 4 @ 3:00 pm – 4:00 pm
Colloquium:Inclusive Astronomy @ BX102

NMSU Inclusive Astronomy

Inclusive Astronomy group, NMSU

Colloquium: Simon Casassus (Host: Wlad Lyra)
Sep 11 @ 3:00 pm – 4:00 pm
Colloquium: Simon Casassus (Host: Wlad Lyra) @ BX102

Protoplanetary disk rotation curves and the kinematic detection of protoplanets

Simon Casassus, Universidad de Chile

Direct detections of protoplanets still embedded in a gaseous protoplanetary disk have been remarkably elusive in their thermal-IR radiation. Yet most models for the structures observed in disks involve planet/disk interactions. The gas and dust density fields are thus appealing proxies to trace embedded bodies, but they are not sufficient to ascertain a planetary origin. New hopes for protoplanet detection come from the disk kinematics, which should also bear their dynamical imprint. The last couple of years have seen the first indirect detection of protoplanets, with the observation of small deviations from Keplerian rotation in molecular line channel maps, and their reproduction in hydrodynamical simulations. Can we use the gas kinematics directly to pin-point the location and measure the dynamical mass of giant planets? The theoretical velocity reversal along the wakes of a protoplanet should be observable as a Doppler-flip, provided that the background flow is adequately subtracted. This axially symmetric flow is a generalized rotation curve, including also the radial and vertical velocity components, which bear the imprint of accretion, winds, and of the theoretical meridional flows in the case of planet/disk interactions. I will present a technique to calculate disk rotation curves, with applications to ALMA long baseline data in HD100546 and in HD163296.

Colloquium: Nikole Nielsen (Host: Chris Churchill)
Sep 18 @ 3:00 pm – 4:00 pm
Colloquium: Nikole Nielsen (Host: Chris Churchill) @ online

The Circumgalactic Medium at Cosmic Noon with KCWI

Nikole Nielsen, Swinburne University of Technology

The star formation history of the universe reveals that galaxies most actively build their stellar mass at cosmic noon (z=1-3), roughly 10 billion years ago, with a decrease toward present-day. The resulting metal-enriched material ejected from these galaxies due to supernovae and stellar feedback is deposited into the circumgalactic medium (CGM), which is a massive reservoir of diffuse, multiphase gas out to radii of 200 kpc. The CGM is the interface between the intergalactic medium and the galaxy, through which accreting filaments of near-pristine gas must pass to contribute new star formation material to the galaxy and outflowing gas is later recycled. Simulating these baryon cycle flows is crucial for accurately modeling galaxy evolution. While the CGM is well-studied at z<1, little attention has been paid to the reservoir when star formation is most active due to the difficulty in identifying the host galaxies. The installation of the Keck Cosmic Web Imager (KCWI), an integral field spectrograph, on Keck II has opened a new window to quickly identify galaxies via their Lyman alpha emission at this redshift. I will introduce a new survey to build a catalog of absorber-galaxy pairs at z=2-3 with KCWI. With the combination of HST images, high-resolution quasar spectra, and the cutting-edge KCWI data, this survey aims to examine CGM kinematics and metallicities and relate them to the host galaxy star formation rates and orientations to reveal the baryon cycle at cosmic noon.

Colloquium: Lauren Kahre (Host: Rene Walterbos)
Sep 25 @ 3:00 pm – 4:00 pm
Colloquium: Lauren Kahre (Host: Rene Walterbos) @ Online

Transitioning to Industry from Academia,

Lauren Kahre

A common career path for recent astronomy graduates with a PhD is data science, but it can be difficult to parse through the enormous amount of information on how exactly to transition to this career. I graduated from NMSU in 2019 and transitioned immediately to an industry career in data science. This talk will be a quick background on my career path, how students can get into data science, and what an industry career in data science actually looks like day-to-day.

Colloquium: Mausumi Dikpati (Host: Juie Shetye)
Oct 2 @ 3:00 pm – 4:00 pm
Colloquium: Mausumi Dikpati (Host: Juie Shetye) @ BX102

Colloquium Title

Mausumi Dikpati, HAO

Abstract text