The galaxy zoo is a long running, successful experiment in crowdsourcing classifications of galaxy morphology from volunteers - volunteers who use the platform are shown images of real galaxies, and guided through questions which get them to assign morphology descriptions (like smooth/featured, the number of spiral arms) to the galaxy. However, as surveys resolve progressively larger numbers of galaxies, this approach becomes difficult to scale. But the crowdsourced data is a very valuable resource we still want to exploit, as human volunteers are extremely good at some functions - notably, flagging particularly unusual looking galaxies to astronomers - that statistical approaches struggle with. I will describe a project I worked on in collaboration with some astrophysicists at Oxford that tried to use active learning, where we train a model to classify these galaxies, then use the posterior uncertainty calculated from the model to decide on the most informative galaxies to send out to be labelled by human volunteers, while labelling ‘easy’ galaxies automatically. I will then briefly talk about some follow up work on combining this with 'semi-supervised' methods. As my audience is physicists, I’ll try not too assume too much knowledge of machine learning in my talk.

"Our galaxy and its neighbors move through the universe at a staggering speed of several hundred kilometers every second. This observation has been known since the early 1960s without astrophysicists being able to fully explain the cause. This speed is not due to the general expansion of the universe, but rather to the gravitational force generated by the matter distributed around us. In the 1990s, an American team of cosmologists, researchers working to understand the laws that govern the universe as a whole, proposed the model of a ""great attractor"", located in a region of the universe hidden from our view. My specialty is called cosmography. It is a question of mapping the positions and the movements of the galaxies, in order to understand which physical laws give birth to these celestial architectures which we observe in the distribution of the luminous matter. In this quest, we discovered with my team, the super continent of galaxies in which we live: ""Laniakea"", reformulating the concept of our local cartography with terms derived from hydrography: watersheds and rivers are now extra-galactic. In this seminar, I will present this discovery and the rest of the research: with observational campaigns using telescopes located in Hawaii, Australia, in space and data from Arecibo! I will also explain the methods of analysis that we invented to understand our nearby cosmic environment." Hélène Courtois is a French astrophysicist specializing in cosmography. She is Professor and Vice President at the University of Lyon 1 and the director of a research team at the Lyon Institute of the two infinite. She received the 2018 Scientist of the Year Award from the French Ministry of Foreign Affairs for her international influence. She is featured in the 2019 documentary Cosmic Flows: The Cartographers of the Universe by CPB Films. 

Microquasars, the local siblings of extragalactic quasars, are binary systems comprising a black hole of several to tens of solar masses and a companion star. By accreting matter from their companions, microquasars launch powerful winds and jets, influencing the interstellar environment around them. Steady gamma-ray emission is expected to rise from their central objects, or from interactions between their outflows and the surrounding medium. The latter prediction was recently confirmed with the detection at the highest (TeV) energies of SS 433, one of the most interesting microquasars known. We analyzed more than ten years of GeV gamma-ray data on SS 433. Detailed scrutiny of the data reveal emission associated with a terminal lobe of one of the jets and with another position in the SS 433 vicinity, co-spatial with a gas enhancement. Both gamma-ray sources are relatively far from the central binary, and the latter shows evidence for a periodic variation at the precessional period of SS 433, linking it with the microquasar. This result challenges obvious interpretations and is unexpected from any previously published theoretical models. It provides us with a chance to unveil the particle transport from SS 433 and to probe the structure of the local magnetic field in its vicinity. Dr. Jian Li pursued his Ph.D. jointly at Institute of High Energy Physics, China and Institute of Space Sciences, Spain. Currently he is a Humboldt Fellow at the Deutsches Elektronen-Synchrotron DESY, Germany. Dr. Jian Li's research is mainly aimed at understanding particle acceleration process and high energy emission mechanism in Galactic sources, in a multi-wavelength context. Dr. Jian Li's research topics cover binaries, pulsars and their related nebulae, magnetars, supernova remnants, and other Galactic compact objects.

We conducted a high-sensitivity survey (~5mJy RMS) for spectral lines in the 6 to 7.4 GHz frequency range with the 305m Arecibo Telescope. We observed a sample of 12 intermediate-/high-mass star-forming regions that included a broad range of evolutionary stages, from Hot Molecular Cores to regions prior to the development of ultra-compact HII regions. The low RMS of our observations allowed us to investigate the nature of spectral features undetectable in previous low-sensitivity surveys, including absorption lines of excited OH and weak variable masers. A main focus of this work is the characterization of 6.7GHz methanol absorption. Even though this transition can be detected in absorption against the Cosmic Microwave Background, we find that most of the known 6.7GHz methanol absorption lines are associated with active sites of high-mass star formation, and that the absorption is likely against compact radio continuum sources in the regions. This work is currently accepted for publication in Monthly Notices of the Royal Astronomical Society, and is available in https://arxiv.org/pdf/2006.11817.pdf Mr. Wei Siang Tan is a graduate from the Master's Program in Physics at Western Illinois University, where he worked with Dr. E. D. Araya on observations and analysis of Arecibo data. He has continued the collaboration with Dr. Araya since then and he is now involved in analysis of GBT observations of 14 GHz formaldehyde emission and follow-up VLA observations of the Arecibo sample. Mr. Tan is currently in Singapore and plans to continue PhD studies in radio astronomy.

Saturn's moon Titan has a methane cycle with clouds, rain, rivers, lakes, and seas; it is the only world known to presently have a volatile cycle akin to Earth’s tropospheric water cycle. Anomalously specular radar reflections (ASRR) from Titan's tropical region were observed with the Arecibo Observatory (AO) and Green Bank Telescope (GBT) and interpreted as evidence for liquid surfaces. The Cassini spacecraft discovered lakes/seas on Titan, however, it did not observe lakes/seas at the AO/GBT anomalously specular locations. A satisfactory explanation for the ASRR has been elusive for more than a decade. Here we show that the ASRR originate from one terrain unit, likely paleolakes/paleoseas. Titan observations provide ground-truth in the search for oceans on exoearths and an important lesson is that identifying liquid surfaces by specular reflections requires a stringent definition of specular; we propose a definition for this purpose. Jason’s research is focused on understanding the physics of present-day active geologic processes in the outer solar system. As a graduate student, he led the Cassini RADAR team in the first discovery and later confirmation of transient features in the hydrocarbon seas of Saturn’s moon Titan. These enigmatic features, popularly known as "Titan's Magic Islands" were determined to be waves, floating or suspended solids, or bubbles. As a NASA Postdoctoral Program Fellow, Jason contributed to the first measurement of the Bond albedos of Pluto and Charon and led the New Horizons team in a search for temporal changes on Pluto and Charon. Pluto was found to have terrains with extraordinarily different albedos and several enigmatic features, which are the focus of a new research project. Jason's current research includes resolving a decade-old apparent discrepancy between Arecibo Observatory and Cassini RADAR observations of Titan and thermal modeling of Kuiper belt object Eris to test the putative explanation of atmospheric freeze-out for its exceptionally high albedo.

We conducted a high-sensitivity survey (~5mJy RMS) for spectral lines in the 6 to 7.4 GHz frequency range with the 305m Arecibo Telescope. We observed a sample of 12 intermediate-/high-mass star-forming regions that included a broad range of evolutionary stages, from Hot Molecular Cores to regions prior to the development of ultra-compact HII regions. The low RMS of our observations allowed us to investigate the nature of spectral features undetectable in previous low-sensitivity surveys, including absorption lines of excited OH and weak variable masers. A main focus of this work is the characterization of 6.7GHz methanol absorption. Even though this transition can be detected in absorption against the Cosmic Microwave Background, we find that most of the known 6.7GHz methanol absorption lines are associated with active sites of high-mass star formation, and that the absorption is likely against compact radio continuum sources in the regions. This work is currently accepted for publication in Monthly Notices of the Royal Astronomical Society, and is available in https://arxiv.org/pdf/2006.11817.pdf Mr. Wei Siang Tan is a graduate from the Master's Program in Physics at Western Illinois University, where he worked with Dr. E. D. Araya on observations and analysis of Arecibo data. He has continued the collaboration with Dr. Araya since then and he is now involved in analysis of GBT observations of 14 GHz formaldehyde emission and follow-up VLA observations of the Arecibo sample. Mr. Tan is currently in Singapore and plans to continue PhD studies in radio astronomy.

Apertif is a new phased-array feed for the Westerbork Synthesis Radio Telescope (WSRT), greatly increasing its field of view and turning it into a natural survey instrument. On 1 July 2019, the Apertif legacy surveys commenced. These are a time-domain survey and a two-tiered imaging survey, with a shallow and medium-deep component. The time-domain survey is searching for new fast radio bursts (FRBs) and monitoring known FRBs to identify repeating sources and improve their localization. The imaging surveys provide neutral hydrogen (HI), radio continuum and polarization data products across a bandwidth of 300 MHz, corresponding to a redshift of 0.26 for HI. The key science goals to be accomplished by by Apertif include localization of FRBs (including real-time public alerts), the role of environment and interaction on galaxy properties and gas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radio population, and studying magnetic fields in galaxies. First results from the surveys include the detection of multiple FRBs (including sources with high rotation measures), the discovery and monitoring of an intra-hour variable, resolved spectral indices from combining with LOFAR data, and more. Survey data products are served to the community via the Apertif Long Term Archive (ALTA). A first, test data release occurred at the end of last yera, and the first survey data release is planned for the near future. Available data products include high-time resolution filterbank data in the PSRFITS standard for the time-domain survey and, for the imaging surveys, raw visibilities, calibration tables, calibrated visibilities, multi-frequency synthesis continuum images, polarization images and cubes, and uncleaned neutral hydrogen (HI) line and beam cubes. I earned my PhD at Cornell University studying isolated gas clouds in the ALFALFA survey as potential gas-bearing ultra-faint dwarf galaxies. I then went to ASTRON as a postdoc, where I continued HI-based studies of dwarf galaxies. In 2017 I became a staff member at ASTRON as a NWO-WISE fellow and led the Apertif imaging commissioning until the start of the Apertif surveys in mid 2019. I have served as the Head of Apertif Science Operations since the start of Apertif survey observations.

The poles of Mercury harbor ice deposits that are several meters thick and interpreted to be >95% pure water ice. The physical properties, composition, and age of the ice can provide critical insight into its origin and evolution. In this seminar, we will discuss our understanding of Mercury's polar ice deposits, and explore how future ground-based exploration can support science investigations of Mercury's polar deposits.

"The Zwicky Transient Facility (ZTF) is a sky survey covering 3750 sq. degrees down to 20.5 mag from the Palomar 1.2m telescope. It has been functional for close to two years, and with its field of view of ~47 square degrees the publicly released DR2 boasts of over 100 billion detections in g//r/i filters. We will describe the data release and how it can be widely used for archival studies. We will emphasize the real-time and time-domain wonders from the survey with rapid follow-up of gravitational wave events as well as its plethora of discoveries including thousands of supernovae, several tidal disruption events, first atiras/vatiras and so on. We will finish by putting it in perspective with surveys to come including ZTF Phase II and the Vera Rubin Observatory (formerly LSST)."

The 2019-20 earthquake sequence in southern Puerto Rico between Guanica and Guayanilla occurred along a paired fault system at the eastern end of the Southwest Puerto Rico seismic zone and the western margin of the Guayanilla Canyon.The primary faults that constitute the zone of earthquake activity are the Punta Montalva Fault and a previously unnamed submarine fault mapped along the upper portions of the western Guayanilla Canyon. The Punta Montalva Fault extends from southern coast of Ensenada Las Pardas, Guanica to the North side of the Parguera Hills, Lajas.Displaced surface drainage patterns (hoyas) between Ensenada Las Pardas and Punta Montalvaindicate 200 meters of left lateral strike slip (horizontal) displacement. Relative motion along fault is to the West on the north side of the Fault and to the East on south side of the fault.The submarine extension of the fault intersects the fault mapped in the Guayanilla Canyon. The Guayanilla CanyonFault is mapped as normal faultinclined to the Northwestwith downward vertical motion Northwest of the mapped trace of the fault.The earthquake sequence initiated with primarily lateral displacementalong the Punta Montalva Fault followed by larger normal displacementsincludingthe largest 6.4 magnitude earthquake on January 7, 2020. The normal fault displacement earthquakes are restricted to a zone Northwest of the Guayanilla Canyon Fault and North of the Puta Montalva Fault.

Radar observations have been playing vital roles in our understanding of many fantastic phenomena in the Earth's upper atmosphere such as Polar mesosphere Summer Echoes (PMSEs) and micrometeoroid influx. However, until recently, most of the observations were not calibrated by any standard method, but rather utilized signal-to-noise ratio (SNR) as the detection threshold, which is closely dependent on the radar's system parameters and experimental configurations, as well as the background noise level. These uncertainties have impeded our ability to understand the absolute signal strengths of the measurements, and complicated the cross-comparisons among sites. In this talk, I will focus on how multiple radars are utilized to understand the geographical distribution of PMSEs. The radars are calibrated using a standard method and cross-comparisons of measurements are performed in absolute units. The results indicate that PMSEs could be influenced by several factors other than the well known extremely low temperate and the availability of water vapor in the polar mesosphere. We also use a similar standardized technique with modeling efforts to perform cross-comparisons of micrometeoroid influx in the Earth�s upper atmosphere among multiple radar sites. In this case, we model the altitude distribution for the radar detection of meteor head plasma reaching the upper atmosphere with a range of masses, velocities, and entry angles, and use it as a proxy to determine and cross-compare the micrometeoroid influx among multiple radars including the Arecibo system.

Arecibo Observatory (AO) has long been the best instrument anywhere for studying pulsars. Its unmatched sensitivity and versatility led to many key early discoveries, and two major upgrades over half a century have since maintained its pre-eminent position in the pulsar astronomy field. The talk will provide an introduction to pulsar physics and astronomy with emphasis on AO�s development, contributions and centrality in the speaker�s personal research.

One of the most striking predictions of general relativity is the formation of black holes and their corresponding horizons, surfaces that act as one-way membranes for energy, matter and information. Testing the latter prediction is particularly subtle but, at the same time, the formation of these membranes has critical implications for the nature and internal structure of black holes, leading to a number of theoretical problems that remain to be solved. Some proposed solutions to these problems involve long-range modifications of general relativity that should be testable both with electromagnetic and gravitational waves. In this talk, I will summarize the motivation behind these theoretical proposals, and discuss possible ways in which observations can constrain them.

Comet 2I/Borisov was first observed September 8, 2019 and was quickly identified as originating from outside the Solar System due to its highly eccentric, hyperbolic orbit. This is only the second such body that has been detected, after 1I/�Oumuamua, which unlike Borisov, showed no coma. The presence of this coma in Borisov may indicate an icier composition with sublimating volatiles. One way of studying the composition of this coma is through radio observations, which can be used to measure the presence of the hydroxyl (OH) radical in the comet�s coma. The OH radical is a photodissociation product of water and can be used to quantify the activity of the comet. Spectroscopy of the OH lines in comets using the Arecibo Observatory has been successfully performed for Solar System comets. We observed interstellar comet 2I/Borisov throughout its passage over the northern sky in the fall of 2019 at the OH line frequencies accessible to Arecibo. Though the OH line was not detected in our observations, we estimate an upper limit to the OH production rate of 6.98 x 10^27 mol/s and an upper limit to the water production rate of 6.49 x 10^27 mol/s. Our results agree with reported optical, near-IR and UV observations of Borisov, which are consistent with low water production. 2I/Borisov did not undergo significant outbursts during our observations.

VHF radar echoes are of origin of refractive index fluctuations and its gradient. These fluctuations are of turbulence. Atmospheric turbulence studies are mostly made by refractive index fluctuation induced radar echoes. These echoes are expected to be an intermittent in space and time since turbulence are highly intermittent in space and time. VHF radar echoes are characterized by different techniques for basic understanding on it and then those echoes are used to study atmospheric turbulence. A new method is being developed for turbulence studies since radar estimated spectral width method has inherent problem. VHF radar echoes from the low latitude mesosphere have been extensively studied using the Jicamarca radar located in Peru and more recently using the MST radar located at Gadanki. This study focuses on studying the low latitude mesospheric echoes extending up to the mesospause (which is ~100 km), which include echoes generated by neutral turbulence below 80 km an! d by plas ma instability above 87 km, turbulence characteristics, and the governing dynamics. Studies have been done using observations made by ground based radars (MST, MF, meteor radars), lidar and ionosonde; rocket borne Langmuir probe; and satellite. Observations have revealed that radar echoes during daytime are observed from two height regions: 60-80 km and 87-102 km. The echoes observed in the height region of 65-80 km are observed in all beam direction while the echoes from 87-102 km are observed in the direction that satisfies perpendicularity to earth�s magnetic field. The echoes from 65-80 km are attributed to the electron density fluctuations generated by neutral turbulence in the mesosphere and are referred to as low latitude mesospheric echoes while the echoes from the 87-102 km are attributed to field aligned electron density irregularities in the E region generated by plasma instability and are referred to as low latitude E region echoes. Both are found to be govern! ed direct ly or indirectly by the neutral dynamics. These findings indicate that the refractive index fluctuations responsible for VHF radar echoes from the low latitude mesosphere are related to neutral turbulence and the turbulence is closely linked with gravity wave activities. These results are discussed inthe light of current understanding on the governing processes and dynamical forcing generating the low latitude mesospheric echoes. Echoes from MLT region are also depends on electron density of that region. Retrieval of electron density has been attempted in D and E region using Incoherent Scattering Radar (ISR) technique and this same technique has also been applied to upper atmosphere/ionosphere.

Man-made Radio Frequency Interference, or RFI, has increasingly invaded the electromagnetic spectrum of interest to radio astronomers, and can seriously hinder sensitive measurements of the radio sky from most locations on the Earth, particularly at lower radio frequencies (below about 2 GHz) where several interesting new investigations with newer instruments have been proposed. Over the past decades, a number of techniques have been developed to characterize and mitigate the RFI. However, the mitigation strategies, often developed to deal with specific RFI situations, have largely been found wanting due to their lack of broader applicability. The talk will attempt to highlight the issues and challenges involved, as well as present a few possible detection and excision techniques, illustrated and assessed through relevant case studies.

The dryness of the region makes it ideal for aeronomical experiments relying on clear skies conditions and low cloud coverage throughout the year. Because of that, several optical instruments are operated at ALO since 2009 in a continuous base. The aeronomical instrument suit corresponds to a word-class resonance W/T Na Lidar system, a 40 kW Enhanced Meteor Detection Radar operating at 60 MHz, an OH mesosphere temperature mapper, and several all-sky nightglow imagers equipped to observe the space-time variations of the OH(6-2), O2(0-1), O(1S), O(1D), and Na nightglow brightness. In this talk, we want to show the different aspects of the lidar observatory and discuss the science investigation enabled by this set of instruments. We will show a number of important results obtained in the past few years and the endeavors we want to pursue in�the near future.

High-mass stars are responsible for some of the most spectacular astronomical objects such as supernova remnants and stellar mass black holes. Massive stars form in giant molecular clouds, generate copious amounts of ionizing photons responsible for the development of HII regions, and drive massive molecular outflows that are thought to contribute to the dissipation of their natal clouds. This talk presents highlights of a multiscale effort to search and characterize atomic and molecular tracers of jets, outflows and the expansion of ionized regions associated with young high-mass stellar objects. The presentation focuses on molecular transitions (masers and absorption lines) and radio recombination lines observable with Arecibo and the VLA

More than 100 small molecular clouds exist at Galactic latitudes b > |25| deg., a subset of which have LSR velocities in the range of (+/-) 20-90 km/s. These objects, known as Intermediate-Velocity Molecular Clouds (IVMCs) have infalling motion that is inconsistent with differential galactic rotation, and studies show that some of these objects may lie at the disk-halo interface. Given their dynamics and locations, IVMCs may represent gas originating in the Galactic fountain or the halo. As there are only 11 known IVMCs to date, we are using Arecibo Observatory to search dozens of candidate IVMCs for the presence of OH 18 cm emission. I will discuss the nature of these clouds, some updates on our current project at Arecibo, and the importance of�possible IVMC detections with respect to understanding the Milky Way's gas cycle