Journal Club Archive
Journal Club Cancelled: Refreshments will be available for social time
Light refreshments will be served at 3:45 pm.
Talks will begin promptly at 4:00 pm.
Each talk will last 20 minutes, with 10 minutes dedicated to Q/A and changeover between speakers.
The speakers are:
Jada Louison: Title: HST/WFC3 Hα Direct-Imaging Detection of a Point-like Source in the Disk Cavity of AB Aur
and
Miriam Eleazer: Title: GOALS-JWST: Mid-Infrared Spectroscopy of NGC 7469
Lisiyuan Yang:
Title: Efficient Formation of Massive Galaxies at Cosmic Dawn by Feedback-Free Starbursts
Jenny Zhang:
"SDSS-IV MaNGA: Bayesian analysis of the star formation history of low-mass galaxies in the local Universe "
https://academic.oup.com/mnras/article/497/4/4753/5891243
Sophia Flury:
"Connection Between Galactic Outflows and the Escape of Ionizing Photons"
https://ui.adsabs.harvard.edu/abs/2022ApJ...940..160M/abstract
1. Yvonne Ban
2. Sandra Bustamante
1. Lisiyuan Yang
2. Andrew Mizener
1.Yingjie Cheng
2.Roxana Popescu
"Spatially Resolved Stellar Populations of Strongly Lensed Quiescent Galaxies"
"Completing the protostellar luminosity Function in Cygnus-X with SOFIA/FORCAST Imaging"
Abstract:
We present a new SOFIA/FORCAST mid-IR survey of luminous protostars and confused star-forming environments in Cygnus X, a nearby million-solar mass molecular cloud complex. We derive bolometric luminosities for over 1000 sources in the region with these new data in combination with extant Spitzer and UKIDSS photometry, with 63 new luminous protostar candidates identified by way of the high quality SOFIA/FORCAST data. By including FORCAST data, we construct protostellar luminosity functions (PLFs) with improved completeness at the high luminosity end. The PLFs are well described by a power law function with an index of ∼−0.5. Based on the Herschel temperature and column density measurements, we find no obvious dependence of the PLFs on the local gas temperature, but PLFs in regions of high stellar density or gas column density exhibit some excess at higher luminosities. Through the comparison between our observed PLFs and existing accretion models, both the turbulent core (TC) and the competitive accretion (CA) models are consistent with our results, while the isothermal sphere (IS) model is disfavored. The implications of these results on the star formation process are discussed.
"The Role of Stellar Feedback in Lyman Continuum Escape"
Abstract
Recent surveys of galaxies emitting Lyman continuum (LCEs) have greatly improved our ability to identify the population of galaxies responsible for cosmic reionization. However, the mechanisms facilitating that escape are poorly understood. Using stacked HST/COS spectra of z~0.3 LCEs, we determine observational constraints on stellar feedback and related ISM conditions in galaxies leaking ionizing photons. With these constraints, we build a simple model framework for understanding the role of feedback in Lyman continuum (LyC) escape wherein stellar winds and supernovae contribute to an evolving H II superbubble. To test this framework self-consistently, we use photoionization models to predict nebular emission line flux ratios and compare the result to observations of the same LCEs from the stacking analysis. We find good agreement between the predicted and observed flux ratios, suggesting that our feedback model is a plausible description of how feedback enables LyC photons to escape their host galaxies.
"The Differential Assembly of the Centers and Outskirts of Main Sequence Galaxies at z~2.3"
1. Nat DeNigris: “A high-resolution view of the filament of gas between Abell 399 and Abell 401 from the Atacama CosmologyTelescope and MUSTANG-2” (Hincks et al. 2021)
2. Maike Clausen: “From starburst to quiescence: post-starburst galaxies and their large-scale clustering over cosmic time” (Wilkinson et al. 2021)
3. Sarah Bodansky: “The MOSDEF Survey: Implications of the Lack of Evolution in the Dust Attenuation-Mass Relation to z~2” (Shapley et al. 2021)
4. Jed McKinney: “Do the properties of dust evolve with redshift?” (Shapley et al. 2021, Clarke et al. 2019, Donevski et al. 2020)
1. Patrick Kamieneski: “Turbulent magnetic fields in the merging galaxy cluster MACS J0717.5+3745: polarization analysis” (Rajpurohit et al. 2021)
2. Andrew Mizener: "Early Science with the Large Millimeter Telescope: a 1.1 mm AzTEC Survey of Red-Herschel dusty star-forming galaxies" (Montaña et al. 2021)
3. Ben Gregg: “The spatial relation between young star clusters and molecular clouds in M51 with LEGUS” (Grasha et al. 2019)
4. Darren Stroupe: “Giant Metrewave Radio Telescope Detection of HI 21 cm Emission from Star-Forming Galaxies at z ≈ 1.3” (Chowdhury et al. 2021)
1. Michael McCracken: “Herschel Photometric Observations of LITTLE THINGS Dwarf Galaxies” (Cigan et al. 2021)
2. Alyssa Sokol: “Impact of relativistic jets on the star formation rate: a turbulence-regulated framework” (Mandal et al. 2021)
3. Carlos Diaz: “The mass and galaxy distribution around SZ-selected clusters” (Shin et al. 2021)
4. Roxana Popescu: “The Colors and Sizes of Recently Quenched Galaxies: A Result of Compact Starburst before Quenching” (Wu et al. 2020)
1. Luan Luan: “Fast galaxy bars continue to challenge standard cosmology” (Mahmood et al. 2021)
2. Joyce Caliendo: “ALMA Measures Rapidly Depleted Molecular Gas Reservoirs in Massive Quiescent Galaxies at z~1.5” (Williams et al. 2021)
3. Sam Cutler: “The Milky Way’s bar and bulge revealed by APOGEE and Gaia EDR3” (Queiroz et al. 2020)
The speakers will be reviewing papers that are directly connected to their own research projects, and will comment about how the selected papers are relevant to their graduate work.
1. Sarah Betti: “Possible evidence of ongoing planet formation in AB Aurigae: A showcase of the SPHERE/ALMA synergy.” (Boccaletti et al. 2020)
2. Yingjie Cheng: “The Single-cloud Star Formation Relation” (Pokhrel et al. 2021)
3. Lisiyuan Yang: “Column Density Profiles of Cold Clouds Driven by Galactic Outflow” (Cottle et al. 2018)
The speakers will be reviewing papers that are directly connected to their own research projects, and will comment about how the selected papers are relevant to their graduate work.
1. Sandra Bustamante: “Black hole parameter estimation with synthetic very long baseline interferometry data from the ground and from space” (Roelofs et al. 2021)
2. Sophia Flury: “No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at 3.1 < z < 3.5” (Saxena et al. 2021)
3. Zhiyuan Ji: “Rotation Curves in z~1-2 Star-Forming Disks: Evidence for Cored Dark Matter Distributions” (Genzel et al. 2020)
Talk held during Colloquium time
Talk held during Colloquium time
Talk held during journal club spot
Nat DeNigris:
Wolf-Rayet Stars in the Antennae unveiled by MUSE https://arxiv.org/pdf/2010.09781.pdf
5 student talks of 10 minutes each
Graduate Student Yingjie Cheng: Quantifying starburst feedback via X-ray spectroscopy of 30 Doradus
X-ray observations provide a potentially powerful tool to study the starburst feedback and its impact on the surrounding medium. So far, the analysis and interpretation of such observations remain challenging, due to various complications including the non-isothermality of the X-ray-emitting hot plasma, and the inhomogeneity of the foreground absorption. To illustrate such complications and mitigate their effects, we present a spatially resolved X-ray spectroscopic study of 30 Doradus in the Large Magellanic Cloud (LMC), based on a 100 ks Suzaku
observation. The high sensitivity and spectral resolution of this observation, together with the proximity of this starburst region, enable us to measure the thermal and chemical properties of the diffuse hot plasma, and to quantitatively confront them with the feedback expected from embedded massive stars. Spectral analysis shows that the plasma temperature varies spatially in the range of 2.5x10^6 K, indicating that it is significantly non-isothermal. We thus characterize the temperature distribution of the plasma emission measure with a log-normal model, which improves the fits to the data. The metal abundances of the plasma are typically 1-2 times higher than the average values of the host galaxy, and the total mass of the plasma is derived as 1-2x10^4 Msun From these estimates, the total metal enrichment is consistent with the expected ejection from the central stellar cluster with two age components of 2 Myr and 4 Myr and that ~62% of the plasma is mass-loaded from the ambient medium. We further conclude that our spatially resolved measurements can be reasonably well reproduced by a global modeling of 30 Doradus with a log-normal temperature distribution and log-normal differential foreground absorption. This log-normal distribution model may be suitable for the X-ray spectral modeling of other giant HII regions, especially for which spatially resolved spectroscopy is not practical. Finally, our spectral analysis shows tentative evidence for a diffuse
non-thermal X-ray component, which most likely arises from inverse Compton scattering of strong radiation in the nebula.
Sophia Flury
TITLE: The Low-Redshift Lyman Continuum Survey I. First Insights into LyC Diagnostics
ABSTRACT
The origin of cosmic reionization remains unknown. Because we cannot detect ionizing photons from reionization-era galaxies, we must turn to indirect diagnostics calibrated at low redshift to provide a foundation for future high redshift observations. We present the Low-Redshift Lyman Continuum Survey (LzLCS), which aims to establish these indirect diagnostics while providing insight into the conditions which facilitate the escape of ionizing or “Lyman continuum (LyC)” radiation. While line-of-sight orientation effects produce substantial scatter in all proposed diagnostics, we find compelling evidence for several key relationships. Properties such as star formation rate surface density and Lyα escape are not only useful diagnostics but also offer insight into the nature of the leaking Lyman continuum. LyC emission appears most consistent with an optically-thick ISM, suggesting a porous, orientation-dependent escape scenario. We find LyC leakers are most commonly compact, low-mass galaxies with highly concentrated star formation.
Students are encouraged to bring ideas, tips, and tricks for making compelling science plots. A competition for the best plot is scheduled for Monday, Sept 7th.
Open to everyone
postponed from 12/2 to 12/12 due to snow day
Title: The Pre-Shipment Status of TolTEC: A New Multiwavelength Imaging Polarimeter for the LMT
Abstract: TolTEC is an upcoming millimeter-wave imaging polarimeter designed to fill the focal plane of the 50-m diameter Large Millimeter Telescope (LMT). Combined with the LMT, TolTEC will offer high angular resolution (5”-10”) for simultaneous, polarization-sensitive observations in three wavelength bands: 1.1, 1.4, and 2.0 mm. Additionally, TolTEC will feature mapping speeds greater than 2 deg^2/mJy^2/hr enabling wider surveys of large-scale structure, galaxy evolution, and star formation than is currently possible at these resolutions. We intend to commission TolTEC at the LMT in Winter 2020. In this talk, I will provide an update on TolTEC’s in-lab testing occurring at UMass Amherst in preparation for installation at the LMT. The improvements that TolTEC will offer are only possible through the integration of three separate focal planes totalling approximately 7000 low-noise, high-responsivity superconducting Lumped Element Kinetic Inductance Detectors (LEKIDs). As of November 2019, we have integrated and tested two of the three detector arrays (1.1 mm and 2.0 mm) to determine their responsivity and, where possible, their bandpasses. I will conclude my talk with some of the novel galaxy cluster physics I hope to study with TolTEC using the Sunyaev-Zel’dovich Effect.
Open to everyone
Title: The Gas Physics of Interacting Galaxies: Feedback and Ram Pressure in NGC4631 and NGC4319
Abstract: We present a panchromatic study of two spiral galaxies (NGC4631 and NGC4319) that are involved in galaxy-galaxy interactions and provide unique constraints on the roles played by gas and dust in merger-driven galaxy evolution. NGC4631, the 'Whale Galaxy', is an edge-on spiral undergoing a merger and starburst. Above the midplane in the hot, x-ray emitting halo, O VI emission indicates that there is a kiloparsec-scale outflow originating from the disk. The ratio of far-ultraviolet to 24um emission shows dramatic changes along and perpendicular to the midplane of NGC4631; we suggest that multiple 'chimneys' are present in the disk, including a nuclear outflow that has evacuated the center and is the likely source of the hot gas seen in X-rays. To investigate the origin of the O VI emission, we compare the O VI brightness at several positions above the midplane to the star formation properties of the underlying disk. NGC4319 is a face-on spiral with prominent tidal features that is also going through a merger. We find a large spatial offset between the 21cm and 24um emission, indicative of removal of the atomic gas from the galaxy due to ram-pressure stripping by intragroup gas. This is corroborated by an extraordinarily high molecular gas fraction in the disk (albeit with low overall column density), which is measured through detection of molecular hydrogen absorption lines along the line of sight to a background quasar. However, FCRAO 14m observations indicate that the molecular gas emission is probably centered on the 24um emission. We use the CO, 21cm, and 24um emission to study how the regions of molecular gas and star formation can be physically separated from the H I gas reservoir in galaxy interactions. We discuss the importance of molecular gas in these processes and how observations of CO rotational emission can provide the missing link for understanding the physics of interacting systems like NGC4319.
Title: Measuring the Heating and Cooling of the Interstellar Medium at High Redshift : PAH and [C II] Observations of the Same Star Forming Galaxies at z ~ 2
Wednesday 11/13 is on a Monday schedule
Open to all
Title: The Role of Environment in Core Evolution: Predictions for the TolTEC Clouds to Cores Legacy Survey
Abstract: Using magnetohydrodynamical simulations of star forming gas with stellar feedback and sink particles (proxies for young stellar objects (YSOs)), we present predictions of synthetic 1.1 mm continuum observations at differing distances (150 - 1000 pc) and ages (0.49 - 1.27 Myr). We characterize how core properties, including mass and size, change with distance, cloud evolution, and the presence of YSOs. We find a clear separation between the size of cores with and without YSOs suggesting evolutionary difference in cores that host YSOs but find little to no temperature dependence on core properties. This separation increases by ∼ 16% with increasing age as cores with YSOs decrease in mass and size. We also find that the atmospheric filtering and core segmentation treatments have distance dependent impacts on the resulting core properties for D < 300 pc and characterize these in detail. These predictions and systematic characterizations will help guide analysis of cores for the upcoming TolTEC Clouds to Cores Legacy Survey on the LMT.
Tuesday 10/15 is on a Monday Schedule
Open to graduate students
Zhiyuan Ji:
Title: Hubble tension between the Early and the Late Universe
Abstract: Predictions made by the Lambda-CDM paradigm has been extensively shown to be consistent with many aspects of modern observational cosmology. The corresponding basic cosmological parameters are being measured with unprecedented precision. Discrepancies between observations in the Early and the Late Universe, however, seem to be confirmed with high significance, which might indicates the requirement of an expansion of the standard cosmological model. In my talk, I will review the different observational technologies of measuring the Hubble constant, both in the Early and the Late Universe, including potential systematics behind different measures. I will also briefly describe the ongoing/near future efforts that astronomers and physics are trying to make to ‘’solve’’ this tension.
Patrick Kamieneski:
Title: The effect of galaxy mergers on star formation rates from z=0-4 The effect of galaxy mergers on star formation rates from z=0-4
Abstract: Galaxy mergers and interactions play a crucial role in our current conception of galaxy evolution and hierarchical structure in the Universe. In the case of some of the most extreme objects yet observed, including Ultra-luminous Infrared Galaxies (ULIRGs) and Dusty Star-forming Galaxies (DSFGs), mergers are often assumed to be at least partially responsible for elevated star formation rates. However, it has been difficult to quantify by how much merger activity typically amplifies star formation. Studying the statistical effect of galaxy mergers on the build-up of stellar mass is fundamental to understanding the growth and evolution of galaxies across cosmic time. In addressing this question, I will present recent results from Pearson et al. 2019, including the use of convolutional neural networks to identify mergers in the SDSS, KiDS, and CANDELS surveys, spanning a redshift range of 0 to 4.
Open to everyone
Open to everyone
Speaker: Dooseok Jung
Title: Investigation into the Star Formation Laws for Starbusting Centers, Disks of Nearby Spiral Galaxies and Starbusts Galaxies
Abstract: We have conducted an analysis of the correlation between surface density of star formation rate (SFR), hydrogen molecular gas mass density and surface density of total gas in a sample of 13 nearby spiral galaxies within 15 Mpc to focus on centers of the galaxies. We measure depletion time in binned regions throughout each galaxy. The goal of this project is to quantify depletion time in the starbursting central regions (SB centers) of several nearby galaxies and compare its values with those of the more quiescent galaxy disks. We use the multiwavelength data in the far-ultraviolet (FUV) from the Galaxy Evolution Explorer (GALEX), mid-Infrared (mid-IR) 24 micron-m from Spitzer Space Telescope Infrared Nearby Galaxies Survey (SINGS), HI from The HI Nearby Galaxy Survey (THINGS) and CO from HERA CO-Line Extragalactic Survey (HERACLES). In the Kennicutt-Schmidt (KS) law plot, the power-law indices are N = 1.134 with molecular gas and N = 2.153 with total gas. We set the standard to identify SB centers which is the ratio between depletion time of each center to the mean value of depletion time in disks for molecular gas of each galaxy is lower than 1/3 and we find six SB galaxies in our sample. The SB centers do not have a strong offset as starburst galaxies (SBGs) do in the universal KS plane for molecular gas, although all of the six SB centers are above the fitted line by data from disks. The SB stars do not show clear evidence for behaving as universal SBGs.
Speaker: Ben Gregg
Title: Quantifying the Molecular Gas in a z=1.75 Galaxy Cluster
Abstract: We present VLA observations of one of the most robustly detected massive galaxy clusters at high redshift, with z=1.75. We characterize this cluster's molecular gas contents by quantifying the strength of CO(1-0) emission within its central regions. We detect one significant CO emission source with a spatial signal-to-noise ratio of 5.29, which is offset from a photometrically determined cluster member galaxy by 2.5 arcseconds (21.5 kpc at z=1.75). We also place 3 sigma upper limits on undetected candidate cluster member galaxies within the half power of our VLA beam. Assuming the association to be accurate, we find that our CO detected galaxy is forming stars at rates that are consistent or below field galaxies with similar stellar mass and molecular gas mass, and that it has significant levels of offset molecular gas with a gas fraction that is consistent with field galaxies at similar redshift. We find our 3 sigma upper limits to indicate that on average the undetected cluster member galaxies are forming stars either on or likely below the main sequence, are consistent with a normal star formation efficiency, and have gas fractions that are similar or likely below that of field galaxies at similar redshift. As a result, we find that our cluster has low molecular gas reservoirs and that its galaxies have low star formation rates and thus we find that our cluster is undergoing the process of quenching. We find our results to be consistent with other blind CO(1-0) surveys of high redshift galaxy clusters, concluding that cluster members galaxies detected in CO have properties resembling that of a star-forming field galaxy with similar stellar mass, gas mass, and redshift.
Zhiyuan Ji & Dooseok Jung
Please note: Wednesday 4/17/19 will follow a UMass Monday schedule
Alyssa Sokol discusses faculty biases towards students: https://www.pnas.org/content/pnas/109/41/16474.full.pdfSupplemental info: https://www.pnas.org/content/pnas/suppl/2012/09/16/1211286109.DC
Supplemental/pnas.201211286SI.pdf?targetid=nameddest%3DSTXT
Luan Luan discusses scientific literacy in ungergraduate students:
https://www.researchgate.net/profile/S_Buxner/publication/258569236_Non-...
Please note: Tuesday 2/19/19 will follow a UMass Monday schedule
