Calendar

Oct
5
Fri
Colloquium: David Nataf (Host: Jason Jackiewicz)
Oct 5 @ 3:15 pm – 4:15 pm
Colloquium: David Nataf (Host: Jason Jackiewicz) @ BX102

Clues to Globular Cluster Formation

David Nataf, Johns Hopkins University

Globular clusters are now well-established to host “Second-generation” stars, which show anomalous abundances in some or all of He, C, N, O, Na, Al, Mg, etc.  The simplest explanations for these phenomena typically require the globular clusters to have been ~20x more massive at birth, and to have been enriched by processes which are not consistent with the theoretical predictions of massive star chemical synthesis models. The library of observations is now a vast one, yet there has been comparatively little progress in understanding how globular clusters could have formed and evolved. In this talk I discuss two new insights into the matter. First, I report on a meta-analysis of globular cluster abundances that combined APOGEE and literature data for 28 globular clusters, new trends with globular cluster mass are identified. I discuss the chemical properties of former globular cluster stars that are now part of the field population, and what can be learned.

Jan
23
Wed
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.

Jan
25
Fri
Pizza Lunch Talk: Dale Frail
Jan 25 @ 11:30 am – 12:30 pm
Pizza Lunch Talk: Dale Frail @ AY 119

How to Write A Competitive Prize Postdoc Application

Dale Frail, NRAO

Colloquium: Dale Frail (Host: Sarah Kovac)
Jan 25 @ 3:15 pm – 4:15 pm
Colloquium: Dale Frail (Host: Sarah Kovac) @ BX102

Multi-Messenger EM-GW Astronomy: The View from the Radio End of the EM Spectrum

Dale Frail, NRAO

Abstract: With the discovery of gravitational waves and electromagnetic radiation from the binary neutron star merger GW170817, the era of GW multi-messenger astronomy has begun with style. I will describe the discovery, show where progress has been made in several areas, and then move on to describe a controversy regarding the origin of the afterglow emission. After explaining the importance of this issue, I will show how late-time radio observations have decisively resolved the issue. I will end with a discussion of the future, with an emphasis on the role of radio observations in finding and studying EM counterparts.

Feb
4
Mon
Planetary Group meeting
Feb 4 @ 3:30 pm – 4:30 pm
Feb
18
Mon
Planetary Group meeting
Feb 18 @ 3:30 pm – 4:30 pm
Feb
20
Wed
Special Colloquium: Stella Kafka (Host: Karen Kinemuchi)
Feb 20 @ 3:15 pm – 4:15 pm
Special Colloquium: Stella Kafka (Host: Karen Kinemuchi) @ Domenici Hall

The AAVSO Program: A Resource for Variable Star Research

Stella Kafka, AAVSO

The AAVSO was formed in 1911 as a group of US-based amateur observers obtaining data in support of professional astronomy projects. Now, it has evolved into an International Organization with members and observers from both the professional and non-professional astronomical community, contributing photometry to a public photometric database of about 25,000 variable objects, and using it for research projects. As such, the AAVSO’s main claim to fame is that it successfully engages backyard Astronomers, educators, students and professional astronomers in astronomical research. I will present the main aspects of the association and how it has evolved with time to become a premium resource for variable star researchers. I will also discuss the various means that the AAVSO is using to support cutting-edge variable star science, and how it engages its members in projects building a stronger international astronomical community.

 

Dr. Stella Kafka, is the Director of the AAVSO (American Association of Variable Star Observers). Before her tenure at the AAVSO, Dr Kafka held positions at CTIO, Spitzer Science center/Caltech, Carnegie Institution of Washington/DTM and AIP Publishing. The AAVSO is an international non-profit organization of variable star observers whose mission is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy.

Feb
22
Fri
Pizza Lunch Talk: Takashi Sekii
Feb 22 @ 12:15 pm – 1:15 pm
Pizza Lunch Talk: Takashi Sekii @ AY 119

Title

Takashi Sekii, National Astronomical Observatory of Japan

Abstract

Mar
1
Fri
Colloquium: RESERVED (Host: TBD)
Mar 1 @ 3:15 pm – 4:15 pm
Colloquium: RESERVED (Host: TBD) @ BX102

Colloquium Title

Colloquium Speaker Name, Affiliation

Abstract text

Mar
4
Mon
Pizza Lunch Talk: Mark Rutkowski
Mar 4 @ 12:30 pm – 1:30 pm
Pizza Lunch Talk: Mark Rutkowski @ AY 119

Ultraviolet Observations of Galaxies

Mark Rutkowski, Minnesota State Univeristy

Ultraviolet observations are essential for answering fundamental questions regarding the role and impact of galaxies in universe. I’ll discuss a number of past, ongoing, and future UV-optical-near IR high redshift surveys with which I am involved and the specific constraints the UV provides on these open questions. Specifically, I’ll highlight the utility of UV observations of starbursts and quiescent galaxies alike for constraining the history of reionization, hierarchical assembly, and (if there’s time) the cosmic history of metals.