2023 Research Projects
Constraining the density profile of a massive galaxy cluster with weak-lensing analysis
Advisors: Ranga-Ram Chary & Kyle Finner
The mass of galaxy clusters is often measured by fitting an analytic model to the radial density profile. The Navarro-Frenk-White (NFW) density model was derived from simulations and is commonly applied to galaxy clusters. Stacks of radial density profiles from many galaxy clusters have been used to show a good agreement with the NFW model. The massive galaxy cluster PLCKG287.0+32.9 (z=0.39) provides an opportunity to analyze the radial density profile of an individual galaxy cluster. Equipped with multi-band Hubble Space Telescope and Subaru Suprime-Cam observations, the weak-lensing signal from the core to beyond the virial radius of PLCKG287 will be used constrain the radial density profile of a galaxy cluster. Popular models, including the NFW, will be compared to the radial profile to explore their validity and test the cold dark matter paradigm.
Building Big Mosaics of the Sky: Studying the Low Surface Brightness Universe with TESS, and more!
Advisor: Bruce Berriman
The images delivered by the Transiting Exoplanet Sky Survey (TESS) offer a unique opportunity probe the low surface brightness Universe, primarily due to the exceptionally deep coverage at the ecliptic poles that is most likely limited only by zodiacal light. Thus, TESS images will enable studies such as derivation of the halo profiles mass of nearby galaxies, tests of Lambda-CDM galaxy formation scenarios, derivation of stellar halo fractions for different mass and morphology galaxies and identification of local stellar streams that cross over sectors and other galaxy cannibalism leftovers. The student will join a small team of scientists and computer scientists analyzing the TESS images to address the science cases just described. The work will have a substantial technological component and will involve using the Montage image mosaic engine to create analysis-ready mosaics of the sky as observed by TESS, including the JWST continuous viewing zone, and to understand the impact of background radiation on the science content of the images. The work will very likely provide the opportunity to perform computations on the Amazon Elastic Cloud. In addition, the student will have the opportunity to create images delivered by TESS (and other missions) for consumption by the World Wide Telescope, an immersive E/PO environment used worldwide.
Galaxy Survey Enhancements with Deep Learning
Advisor: Shoubaneh Hemmati
The success of many of the upcoming large cosmology missions (e.g., LSST, Roman, Euclid, SPHEREx) relies on the precise measurements of the redshifts, shapes, and other physical properties of galaxies. These measurements often require a joint processing of the observations and the higher the spatial and spectral resolution, wavelength coverage, and depth of these observations, the more information they entail. Given the wealth of the galaxy data today and advancements in image processing with deep learning, huge improvements for future surveys and their combinations can come about using data-driven approaches. Through this project, we will design and optimize multi-band image enhancement deep learning structures and explore the extent of spatial/spectral resolution boosting, denoising, and in-filling of hyper-spectral images for future large galaxy surveys by training on the deepest existing multi-band observations in the COSMOS and CANDELS fields. We will quantify the gain in the estimation of various physical properties given the enhanced data products.
Understanding Star Formation and Black Hole Growth in Luminous Infrared Galaxies
Advisor: Lee Armus
Luminous Infrared Galaxies (LIRGs) generate their enormous power through intense starbursts and the fueling of Active Galactic Nuclei (AGN). With the Great Observatories All-sky LIRG Survey (GOALS), we are characterizing a sample of over 200 low-redshift LIRGs across the electromagnetic spectrum. A key part of GOALS is the study of how stars form and black holes grow under these extreme conditions, by observing the atomic and molecular gas and star clusters at high resolution. To this end, we have been obtaining imaging and spectroscopic observations of LIRGs with HST, ALMA, Palomar and Keck/AO in the UV through the sub-mm. The successful candidate will work directly with the GOALS team to reduce, analyze and publish recent observations of the star-forming clusters, molecular gas content, and galactic outflows in four LIRGs observed as part of an awarded JWST Director’s Discretionary Early Release Science (ERS) program (ERS 1328). The four ERS target galaxies (NGC 3256, NGC 7469, II Zw 096 and VV114) will be observed between July 2022 and Jan 2023, using NIRCam, NIRSpec and MIRI to obtain multi-band images and resolved IFU spectra of the centers of each galaxy.
Characterizing High-Redshift Galaxies with ALPINE
Advisor: Andreas Faisst
The ALPINE project is a 70h large ALMA program aimed at characterizing the far infrared (FIR) and [CII] (158um) properties of 4<z<6 galaxies. We seek students to work on combining the extensive existing multi-wavelength imaging and spectroscopy with the ALMA data to conduct a range of studies. This includes also new JWST data over the COSMOS field. A possible project could focus on studying the internal dust attenuation distribution and external environment of some of these galaxies by using data from the Hubble Space Telescope as well as the new JWST NIRCam data (some technical tasks would include extraction of kpc-resolved photometry and SED fitting). The findings can then be related to the evolution of galaxies on the z ~ 5 main sequence and their far-infrared and [CII] properties and dynamics. The student would have access to all ALPINE data and ideas for other projects are welcome.
Unveiling Dynamics and Unique Chemistry in Hot Jupiter Atmospheres with High Resolution Spectroscopy
Advisor: Aurora Kesseli
High resolution transmission and emission spectroscopy has proven a powerful tool for characterizing exoplanet atmospheres. The technique has moved from simply detecting the presence or absence of individual molecules to a point where precise abundances, temperatures, and cloud properties can be teased out of the data using retrieval frameworks. Furthermore, due to the velocity precision that is available with high-resolution spectroscopy, we are able to map wind patterns across the surfaces of planets and compare these data to global circulation modeling to determine how heat is circulated around highly irradiated planets. We will use a wealth of archival data (CARMENES, HARPS, etc.), as well as new observations obtained with the near-infrared PARVI spectrograph on Palomar to fully characterize a hot Jupiter. The graduate student will work closely with Dr. Kesseli as well as other members of the instrument team that are also at IPAC to reduce and analyze the data and lead a publication on the results. Students do not need to have prior experience with high resolution spectroscopy of exoplanet atmosphere, but coding knowledge in Python is recommended.
Microlensing Parallax for Exoplanets Towards the Bulge
Advisor: S. Calchi Novati
The Spitzer team, in part based at IPAC, has been leading a microlensing observational campaign towards the Galactic Bulge following up microlensing events alerted by ground-based surveys with the Spitzer space telescope. The key feature of this project is the possibility to measure the microlensing parallax thanks to the simultaneous observation of the same microlensing event from two distant (d > 1.5 au) observers (from Earth and from Spitzer). The main scientific driver of the project is to build the Galactic distribution of exoplanets (Calchi Novati et al, 2015a, Zhu et al 2017). In addition to ten exoplanets (Udalski et al 2015, Street et al 2016, Shvartzvald et al 2017, Ryu et al 2018, Calchi Novati et al 2018 and 2019, Gould et al 2019, Hirao et al 2020, Konda et al 2021, Yee et al 2021), several additional interesting events (binary systems, high magnification events, single lens with finite source effects) have also been analyzed based on the six years (2014-2019) of data. In addition, relevant work is being done for the analysis of the data (Calchi Novati et al 2015b) and to assess the statistical meaning of the observations (Yee et al 2015b, Zhu et al 2015b). In this framework there are several avenues to pursue, according to the applicant's interests and previous experience: optimizing the photometry of Spitzer data; characterization of microlensing events; evaluation of the detection efficiency.
Prior experience with microlensing is welcomed but not required.
Mining a Billion Objects in NED with Machine Learning
Advisors: Joe Mazzarella & David Cook
The NASA/IPAC Extragalactic Database (NED) joins data across the electromagnetic spectrum from space missions, large ground-based sky surveys, and over 128,000 astrophysics journal articles to provide a panchromatic census of objects beyond our Milky Way Galaxy. Currently nearly 14 billion photometric measurements have been fused on an object-by-object basis to construct first-look spectral energy distributions (SEDs) for over 1.1 billion distinct objects, providing a unique resource for a variety of scientific explorations. We are seeking a visiting
graduate student interested in applying statistical data mining or machine learning algorithms to study the SEDs in combination with new measurements from large spectroscopic and photometric redshift surveys. An initial goal is to classify hundreds of millions of objects that presently lack confident identifications (i.e., star, galaxy, AGN discrimination), using a combination of supervised and unsupervised machine learning algorithms. The student will also estimate physical quantities for newly identified galaxies and AGN, and characterize them statistically. Depending on interests and prior experience, applicants may also propose to focus on a particular subset of the data to conduct a related research project with potential for discovery using NED in a novel way. Students interested in applying their strong skills in data science to study galaxy and AGN populations are encouraged to apply.
Extending Kepler’s understanding of M dwarf planets with K2 and TESS
Advisor: Jesse Christiansen
One surprising result from the NASA Kepler mission was that M dwarfs are incredibly efficient at creating small rocky planets. However, this result was limited to a small number of early M dwarfs. Since Kepler, a number of large datasets have become available (K2 and TESS) which survey an order of magnitude more M dwarfs than Kepler, including a larger number of mid- and late-M dwarfs, and our characterization of the properties of those stars has been significantly revised and refined. Our team has a catalog of uniformly detected planet candidates orbiting a set of uniformly derived M dwarf host stars and has plans to extend Kepler’s results into the mid- to -late M dwarf regime, as well as explore dependencies along other axes like age and metallicity. A visiting graduate student would work with our diverse, multi-institution team to calculate occurrence rates of planets orbiting this cool star sample and explore correlations with system and stellar parameters.
Does the Core Mass Function (CMF) map into the Initial Mass Function (IMF)? A Herschel analysis in nearby molecular clouds
Advisor: Roberta Paladini
The Core Mass Function (CMF) provides a statistical description of the distribution of the natal core masses and represents a unique tool to understand the relation between stars and their parent molecular cloud. Observational studies have started focusing on the CMF only in the last ten - twenty years, with the advent of ground- and, especially, speaced-based sub-millimeter and far-infrared facilities, such as SCUBA, Bolocam, Herschel and, more recently, ALMA.
One of the most accurate determinations of the CMF has been indeed obtained by Herschel observations of the nearby Aquila complex. These observations suggest that the CMF can be described, for M > 0.5 MSun, similarly to its notorious Initial Mass Function (IMF) counterpart, by a Chabrier or Kroupa mass function (dN ~ Mcore(-2 - 2.5) dM) but shifted towards larger masses by a factor ~ 3. This shift is currently interpreted as a core-to-star conversion efficiency of roughly 30%.
The similar shape of the IMF and the CMF has led to believe that there is an intrinsic mapping between these two quantities. However, this one-to-one correspondence does not find much theoretical support. In addition, the CMF has been barely measured across different environments.
The proposed project will allow the student to derive the CMF for an unprecedented number of nearby molecular clouds by using Herschel PACS and SPIRE data. This analysis will provide the first unbiased look at the CMF in our Solar neighborhood, probing molecular clouds forming both low and high-mass stars, and contributing to answer the following questions: is the CMF universal? And does the CMF map directly into the IMF in all environments?
Studying environmental effects of dwarf galaxies at high redshifts
Advisor: Anahita Alavi
In galaxy formation theory, dwarf galaxies (M*<= 109 Msun) are at the forefront of many important questions, but we are only just beginning to constrain their detailed properties, especially at high redshift. Though faint, dwarfs are the most abundant galaxies and thus have likely significant contribution in star formation in the universe. Due to their low gravitational potential, these galaxies are significantly affected by their environments. At low redshifts, the increased prominence of dwarf spheroidals relative to dwarf irregulars with decreasing distance from massive hosts suggests that the presence of larger structures (whether single galaxies or clusters) plays a significant role in star formation suppression. However, the physical mechanism (tidal/ram pressure stripping or strangulation) is not well known, nor is the time scale. With the UVCANDELS data and catalogs, we can examine the effects of environment on dwarf galaxies at high redshifts. Using the WFC3/UVIS camera on board the Hubble Space Telescope, UVCANDELS provides deep (AB∼27) and wide (∼450 arcmin^2) imaging in F275W of four of the CANDELS fields (GOODS-S, GOODS-N, EGS and COSMOS). We seek students to use these unprecedented UV data and catalogs to identify dwarf satellite galaxies and their massive hosts at z~1 and to study how their star formation changes as a function of orbital radius in these systems.
