Stephen Hannon
A5081744020- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Management and Marketing Education
- Reflective Practices in Education
- Spectroscopy and Chemometric Analyses
- Adaptive optics and wavefront sensing
- Advanced Sensor and Control Systems
- Advanced Statistical Methods and Models
- Statistical Methods and Applications
- Scientific Research and Discoveries
- Advanced Vision and Imaging
- Inertial Sensor and Navigation
- Computational Physics and Python Applications
- Higher Education and Employability
Max Planck Institute for Astronomy
2023-2024
NSF’s NOIRLab
2022-2023
University of California, Riverside
2019-2023
Gemini North Observatory
2022-2023
California Institute of Technology
2019-2021
Infrared Processing and Analysis Center
2019-2021
Galway-Mayo Institute of Technology
2005
Abstract The PHANGS project is assembling a comprehensive, multiwavelength data set of nearby (∼5–20 Mpc), massive star-forming galaxies to enable multiphase, multiscale investigations into the processes that drive star formation and galaxy evolution. To date, large survey programs have provided molecular gas (CO) cubes with Atacama Large Millimeter/submillimeter Array, optical integral field unit (IFU) spectroscopy Very Telescope/Multi-Unit Spectroscopic Explorer (MUSE), high-resolution...
Abstract A primary new capability of JWST is the ability to penetrate dust in star-forming galaxies identify and study properties young star clusters that remain embedded gas. In this Letter we combine infrared images taken with our optical Hubble Space Telescope (HST) starbursting barred (Seyfert2) spiral galaxy NGC 1365. We find has richest population massive any known within 30 Mpc, ∼30 are more than 10 6 M ⊙ younger Myr. Sixteen these newly discovered from observations. An examination...
Abstract Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ringlike structures where intense star formation occurs, forming a very different environment compared galactic disks. We pair ∼0.″3 (30 pc) resolution new JWST/MIRI imaging archival ALMA CO(2–1) mapping central ∼5 kpc nearby barred spiral NGC 1365 investigate physical mechanisms responsible for this extreme formation. The gas morphology is resolved into two well-known bright bar...
Abstract The exquisite angular resolution and sensitivity of JWST are opening a new window for our understanding the Universe. In nearby galaxies, observations revolutionizing first phases star formation dusty interstellar medium. Nineteen local galaxies spanning range properties morphologies across star-forming main sequence have been observed as part PHANGS-JWST Cycle 1 Treasury program at spatial scales ∼5–50 pc. Here, we describe pjpipe , an image-processing pipeline developed that wraps...
Abstract The structure and chemistry of the dusty interstellar medium (ISM) are shaped by complex processes that depend on local radiation field, gas composition, dust grain properties. Of particular importance polycyclic aromatic hydrocarbons (PAHs), which emit strong vibrational bands in mid-infrared, play a key role ISM energy balance. We recently identified global correlations between PAH band optical line ratios across three nearby galaxies, suggesting connection heating ionization...
When completed, the PHANGS-HST project will provide a census of roughly 50,000 compact star clusters and associations, as well human morphological classifications for 20,000 those objects. These large numbers motivated development more objective repeatable method to help perform source classifications. In this paper we consider results five galaxies (NGC 628, NGC 1433, 1566, 3351, 3627) using from two convolutional neural network architectures (RESNET VGG) trained deep transfer learning...
The analysis of star cluster ages in tandem with the morphology their HII regions can provide insight into processes that clear a cluster's natal gas, as well accuracy and dust reddening derived from Spectral Energy Distribution (SED) fitting. We classify 3757 clusters 16 nearby galaxies according to H$α$ (concentrated, partially exposed, no emission), using Hubble Space Telescope (HST) imaging Legacy ExtraGalactic Ultraviolet Survey (LEGUS). find: 1) mean SED concentrated (1-2 Myr) exposed...
A long-standing problem when deriving the physical properties of stellar populations is degeneracy between age, reddening, and metallicity. When a single metallicity used for all star clusters in galaxy, this can result $`$catastrophic$'$ errors old globular clusters. Typically, approximately 10 - 20 % detected spiral galaxies have ages that are incorrect by factor ten or more. In paper we present pilot study four (NGC 628, NGC 1433, 1365, 3351) from PHANGS-HST survey. We describe methods to...
Abstract We present the largest catalog to date of star clusters and compact associations in nearby galaxies. have performed a V -band-selected census across 38 spiral galaxies PHANGS–Hubble Space Telescope (HST) Treasury Survey, measured integrated, aperture-corrected near-ultraviolet- U-B-V-I photometry. This work has resulted uniform catalogs that contain ∼20,000 associations, which passed human inspection morphological classification, larger sample ∼100,000 classified by neural network...
The morphology of HII regions around young star clusters provides insight into the timescales and physical processes that clear a cluster's natal gas. We study ~700 (<10Myr) in three nearby spiral galaxies (NGC 7793, NGC 4395, 1313) using Hubble Space Telescope (HST) imaging from LEGUS (Legacy ExtraGalactic Ultraviolet Survey). Clusters are classified by their H$\alpha$ (concentrated, partially exposed, no-emission) whether they have neighboring (which could affect clearing timescales)....
We present the results of a proof-of-concept experiment which demonstrates that deep learning can successfully be used for production-scale classification compact star clusters detected in HST UV-optical imaging nearby spiral galaxies (D < 20 Mpc) PHANGS-HST survey. Given relatively small nature existing, human-labelled cluster samples, we transfer knowledge state-of-the-art neural network models real-object recognition to classify candidates into four morphological classes. perform series...
We present an innovative and widely applicable approach for the detection classification of stellar clusters, developed PHANGS-HST Treasury Program, $NUV$-to-$I$ band imaging campaign 38 spiral galaxies. Our pipeline first generates a unified master source list stars candidate to enable self-consistent inventory all star formation products. To distinguish cluster candidates from stars, we introduce Multiple Concentration Index (MCI) parameter, measure inner outer MCIs probe morphology in...
Context. Stellar feedback is one of the fundamental factors regulating evolution galaxies. However, we still do not have access to strong observational constraints on relative importance different mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving H II region and molecular cloud disruption. To quantify compare mechanisms, size an crucial, whereas samples well-resolved regions are scarce. Aims. We constrain various from young massive star populations by resolving...
ABSTRACT Connecting the gas in H ii regions to underlying source of ionizing radiation can help us constrain physical processes stellar feedback and how evolve over time. With PHANGS–MUSE, we detect nearly 24 000 across 19 galaxies measure properties ionized (e.g. metallicity, ionization parameter, density). We use catalogues multiscale associations from PHANGS–HST obtain constraints on age sources. construct a matched catalogue 4177 that are clearly linked single association. A weak...
ABSTRACT We develop a method to identify and determine the physical properties of stellar associations using Hubble Space Telescope (HST) NUV−U−B−V−I imaging nearby galaxies from Physics at High Angular Resolution in Nearby GalaxieS with (PHANGS–HST) survey. apply watershed algorithm density maps constructed point source catalogues Gaussian smoothed multiple scales 8 64 pc. our on two that span distance range PHANGS–HST sample: NGC 3351 (10 Mpc) 1566 (18 Mpc). test different parameters such...
Currently available star cluster catalogues from HST imaging of nearby galaxies heavily rely on visual inspection and classification candidate clusters. The time-consuming nature this process has limited the production reliable thus also post-observation analysis. To address problem, deep transfer learning recently been used to create neural network models which accurately classify morphologies at scale for spiral (D < 20 Mpc). Here, we use UV-optical over 20,000 sources in 23 Physics High...
ABSTRACT Only about 19 Galactic and 25 extragalactic bonafide luminous blue variables (LBVs) are known to date. This incomplete census prevents our understanding of this crucial phase massive star evolution which leads the formation heavy binary black holes via classical channel. With large samples LBVs one could better determine duration maximum stellar luminosity characterize phase. We search for candidate (cLBVs) in a new galaxy, NGC 7793. For purpose, we combine high spatial resolution...
ABSTRACT We present a pilot library of synthetic NUV, U, B, V, and I photometry star clusters with stochastically sampled IMFs ionized gas for initial masses, Mi = 103, 104, 105 M⊙; t 1, 3, 4, 8 Myr; Z 0.014 0.002; log(US) −2 −3. compare the predictions from deterministic models observations isolated low-mass (&lt;104 M⊙) co-spatial compact H ii regions. The are located in NGC 7793, one nearest galaxies observed as part HST LEGUS Hα-LEGUS surveys. (1) For model magnitudes that only...
Educational programmes should promote an ethos of lifelong learning and develop in graduates the capacity for long-term personal professional development through self-learning reflection. A business degree programme seek to produce who are confident, creative thinkers with solve problems, think creatively, negotiate, make decisions resolve conflict. The these capabilities not be left chance, but addressed explicitly programme. Whether creativity critical thinking skills innate or learned,...
Critical thinking abilities are essential for modern business professionals, particularly in the high value-added knowledge economies of information age. There have been clear and repeated calls improving students’ this regard. Developing graduate critical capability may be achieved a variety ways. One approach is based on experiential learning theory. In developing Bachelor Business Studies (BBS) degree programme (NQAI Level 8) at Castlebar Campus, Galway-Mayo Institute Technology, an...
The exquisite angular resolution and sensitivity of JWST is opening a new window for our understanding the Universe. In nearby galaxies, observations are revolutionizing first phases star formation dusty interstellar medium. Nineteen local galaxies spanning range properties morphologies across star-forming main sequence have been observed as part PHANGS-JWST Cycle 1 Treasury program at spatial scales $\sim$5-50pc. Here, we describe pjpipe, an image processing pipeline developed that wraps...
We present the largest catalog to-date of star clusters and compact associations in nearby galaxies. have performed a V-band-selected census across 38 spiral galaxies PHANGS-HST Treasury Survey, measured integrated, aperture-corrected NUV-U-B-V-I photometry. This work has resulted uniform catalogs that contain $\sim$20,000 which passed human inspection morphological classification, larger sample $\sim$100,000 classified by neural network models. Here, we report on observed properties these...
The structure and chemistry of the dusty interstellar medium (ISM) are shaped by complex processes that depend on local radiation field, gas composition, dust grain properties. Of particular importance Polycyclic Aromatic Hydrocarbons (PAHs), which emit strong vibrational bands in mid-infrared, play a key role ISM energy balance. We recently identified global correlations between PAH band optical line ratios across three nearby galaxies, suggesting connection heating ionization throughout...
A long-standing problem when deriving the physical properties of stellar populations is degeneracy between age, reddening, and metallicity. When a single metallicity used for all star clusters in galaxy, this can result $`$catastrophic$'$ errors old globular clusters. Typically, approximately 10 - 20 % detected spiral galaxies have ages that are incorrect by factor ten or more. In paper we present pilot study four (NGC 628, NGC 1433, 1365, 3351) from PHANGS-HST survey. We describe methods to...
Connecting the gas in HII regions to underlying source of ionizing radiation can help us constrain physical processes stellar feedback and how evolve over time. With PHANGS$\unicode{x2013}$MUSE we detect nearly 24,000 across 19 galaxies measure properties ionized (e.g. metallicity, ionization parameter, density). We use catalogues multi-scale associations from PHANGS$\unicode{x2013}$HST obtain constraints on age sources. construct a matched catalogue 4,177 that are clearly linked single...