National SKA Science Day Sweden

Thursday 2 Feb 2023, 09:00 → 17:15 Europe/Stockholm

Lecture room 24, floor 2 (Albano Hus 4)

Anne-Kathrin Baczko, Martin Sahlén (Uppsala universitet), Michael Lindqvist (Chalmers)

Thank you very much to all participants for attending and making this event successful! You can find the speakers' slides attached in the detailed view of the timetable: https://indico.fysik.su.se/event/7968/timetable/#20230202.detailed

 

You can also find a recording of the event here: https://play.chalmers.se/media/National+SKA+Science+Day+Sweden/0_fk6md8xi

 

 

Following on from the official start of construction of the Square Kilometre Array (SKA), and confirmation of Sweden’s fully financed participation in SKA, a Swedish national SKA Science all-day meeting will be held at Albanova, Stockholm University on Thursday 2nd February, 2023, 10:00 - 17:00. This meeting will be the first chance after the pandemic for Swedish astronomers working in SKA related science to meet and for Swedish researchers in general to learn more about the science opportunities using both SKA itself (whose joint-risk science verification observations will start in 2026 and first PI science programs in 2028); and the science opportunities available using the SKA precursor/pathfinder telescopes that are already operating.

The SKA Observatory Science Director Robert Braun will be attending/presenting at the meeting - in addition to representatives of SKA Precursor/Pathfinder telescopes. Plans for the development of the Swedish node of the SKA Regional Centre Network of archive/computer facilities will also be presented. The largest part of the meeting however will be reserved for contributed presentations from Swedish researchers on their SKA precursor/pathfinder results and their scientific plans for SKA.

 

 

Deadline for registration & submission of abstracts: Wed 18 January 2023 

 

Confirmed Invited Speakers and Provisional Titles

 

Robert Braun (SKAO)  - SKA science case and project status/timeline 

 

Jason Hessels (ASTRON, Netherlands) - Scientific highlights from the metre wavelength SKA precursor telescope LOFAR and LOFAR 2.0 goals.

 

Kelley Hess (IAA-CSIC, Spain) - HI galaxies science results from centimetre wavelength SKA precursor telescopes.

 

Leah Morabito (Durham University, UK) - Scientific exploitation of LOFAR  international baseline observations.

 

Lindsay Magnus (SKA-South Africa) - SKA precursor MeerKAT - Continuum and Transient Highlights (given by remote presentation).

 

SKAO Code of conduct for meetings and events 

https://www.skao.int/en/about-us/ethics#__otpm1

 

Please be advised that a member of the SKAO’s Communications team, Cassandra Cavallaro, will be present to conduct video interviews with some meeting attendees, and to film some “B-roll” shots (without sound) of the meeting in progress. These shots may be used in future SKAO video products. If you have any concerns about this, or would prefer not to be on camera, please contact Cassandra directly: cassandra.cavallaro AT skao.int

 

The meeting will be streamed live on https://chalmers.zoom.us/j/67655122433.

 

We also plan to record the meeting. Kindly let us know if you are giving a talk and do not want it recorded. 

 

Directions.pdf

09:00 → 10:00 Registration: Registration & Coffee

09:50 Welcome

A brief welcome to the meeting on behalf of the LOC

Speaker: Garrelt Mellema (Stockholm University)

10:00 → 12:05 Talks: Morning session

Convener: Martin Sahlén (Uppsala universitet)

10:00 SKA science case and project status/timeline

Speaker: Mr Robert Braun (SKAO)

Robert_BraunSKAO_Update_Jan2023.pdf

10:30 Sweden in the SKA

An overview will be given of Sweden's involvement in the Square Kilometre Array including the following topics:

(1) The national funding secured for Swedish SKA involvement and membership of the SKA Observatory international organisation.

(2) Ongoing work establishing the Swedish node of the SKA Regional Centre (SRC) global network of data centres. The short and long term capabilities of this SRC node for supporting Swedish use of SKA precursor and other radio telescopes will be described.

(3) Technology development and industrial return to Sweden as a template for financing Swedish involvement in flagship international astronomy projects.

Speaker: John Conway (Onsala Space Observatory, Chalmers University of Technology)

SKA-Science-Stockholm-230202-JC-v3.pdf

10:45 Scientific highlights from the metre wavelength SKA precursor telescope LOFAR and LOFAR 2.0 goals.

Speaker: Jason Hessels

Hessels_LOFAR-SKA_Sweden_230202.pdf

11:10 Scientific exploitation of LOFAR international baseline observations.

Speaker: Leah Morabito

Morabito_Sweden_SKA.pdf

11:35 Sub-arcsecond resolution imaging of M51 with LOFAR-VLBI

With the onset of the SKA era, there is renewed focus on the low-frequency radio sky, with many technological advancements from the likes of GMRT, VLITE and the recent VLBI pipeline at 150 MHz with the International LOFAR Telescope (Morabito et al. 2022). In this talk, we present the first sub-arcsecond resolution image of the nearby galaxy M51 with LOFAR-VLBI, with a focus on the resolved radio emission and compact sources in the galaxy, especially supernovae. We compare the LOFAR-VLBI image with a higher frequency VLBI study (an EVN survey of M51; Rampadarath et al. 2015) and discuss supernovae, which have not yet been probed at these low radio frequencies. LOFAR-VLBI opens up uncharted territory to study these cosmic explosions and their interaction with the galaxy environment. Such low-frequency studies help us bridge the gap between our current understanding of various objects in the radio sky and what SKA will bring with it in the future. Last but not least, the technical developments associated with low-frequency instruments like LOFAR-VLBI will also help build calibration methodologies and other capabilities for handling data from the SKA.

Speaker: Deepika Venkattu (Stockholm University)

11:50 Polarization in the ELAIS-N1 LOFAR deep field: Probing the sub-mJy regime of polarized extragalactic sources

We present a polarimetric study at 114.9–177.4 MHz of the European Large Area ISO Survey-North 1 (ELAIS-N1) deep
field, one of the deepest of the LOFAR Two-Meter Sky Survey (LoTSS) Deep Fields so far. An area of 25 deg2 was imaged at 6”-resolution in the Stokes Q,U parameters. A 1σ sensitivity of 17 µJy/beam was reached in the central part by aligning the polarization angles and stacking datasets from 19 eight-hour-long epochs taken in two different observing cycles.
A search for polarization was carried out in the final stacked dataset and the properties of the detected sources were examined, resulting in the deepest and highest-resolution polarization study at 150 MHz to date.
32 polarized sources were detected, of which six were not detected at any other radio frequency before. The sources are weakly polarized, with a median degree of polarization of 1.75%. Most of them are FRII radio galaxies.
The depolarization of sources known to be polarized at 1.4 GHz was quantified and used to constrain models of polarized source counts at 150 MHz.

Speaker: Sara Piras (Chalmers University of Technology)

7.SaraPiras_NationalSKAScienceDay_020223.pdf

12:05 → 13:00 Lunch break

13:00 → 14:25 Talks: Afternoon session 1

Convener: Anne-Kathrin Baczko

13:00 HI galaxies science results from centimetre wavelength SKA precursor telescopes.

Speaker: Kelley Hess

kelley_hess.pdf

13:25 MeerKAT HI imaging of high-redshift analog galaxy Haro11: clues to Reionization

About 400 Myr after the Big bang, the Universe transitioned from primarily neutral to ionized. Primeval star forming galaxies are thought to be the main sources that caused the Reionization of the Universe. However, the way ionizing radiation escaped the neutral gas of galaxies to ionize the intergalactic medium is still poorly understood, due to the limits of high redshift observations. To remedy this, nearby galaxies similar to high-redshift objects can be used to get detailed information on the processes at play during Reionization. Haro 11 is the closest (z~0.02) galaxy with confirmed ionizing radiation escape and is considered an observational laboratory to study reionization from the local perspective. However, a decade of attempts to map the neutral interstellar medium of this galaxy yielded contradicting results. I will present MeerKAT 21cm HI observations of Haro 11 that reveal the neutral gas distribution enabling the escape of ionizing photons in a galaxy for the first time. We found that merger interactions have played an essential role in the escape of ionizing photons to the intergalactic medium. I will discuss how galaxy mergers could contribute to the reionization of the Universe.

Speaker: Alexandra Le Reste (Stockholm University)

AlexLeReste_clues to Reionization.pdf

13:40 Constraining cosmology with the 21-cm signal during reionization

The low-frequency component of the Square Kilometre Array (SKA) will be able to observe the 21-cm signal produced by the neutral hydrogen in the intergalactic medium (IGM) during the epoch of reionization (EoR). Using this signal, we can study the evolution of large scale structures during the Reionization epochs. In this talk, I will present a fast framework to model the signal that is vital for interpreting the upcoming SKA data. I will also show a forecast study highlighting the capability of the expected 21-cm signal from SKA in constraining the cosmological parameters.

Speaker: Sambit Kumar Giri (Stockholm University)

3.Sambit_SwedishSKAMeeting_2023.pdf

13:55 Probing the Cosmic Dawn using the redshifted 21-cm bispectrum

In the evolutionary history of our Universe, the Cosmic Dawn and Epoch of reionization (CD-EoR) is the period when the formation and evolution of the very first luminous sources took place. These first sources transitioned the state of the Universe from cold and neutral to a fully heated and ionized one, together with introducing a high level of non-Gaussianity in the heating and ionization field. The CD-EoR 21-cm radiation from the abundant neutral hydrogen atom (HI) in the inter-galactic medium (IGM) is the direct tracer of heating and ionization processes in the IGM during this era. It thus carries the intrinsic non-Gaussian information present in the field. The power spectrum, which is one of the widely used and conventional statistics as a probe of the CD-EoR 21-cm signal in the current observations of this signal, cannot capture this non-Gaussianity. The bispectrum, being a potential probe of this non-Gaussianity, provides an opening for a comprehensive and correct interpretation of this signal. We, for the first time, explore how the bispectrum, probing the non-Gaussianity, can provide better insights into IGM physics during CD-EoR. This will help us in interpreting the future observations of the CD-EoR 21-cm signal using the upcoming Square Kilometer Array (SKA) once the interferometric detection of this signal has been made possible.

Speaker: Mohammad Kamran (Uppsala University)

4.Kamran_Mohd_SKA_meeting_Sweden.pdf

14:10 Utilization of Convolutional Neural Networks for H i Source Finding Team FORSKA-Sweden approach to SKA Data Challenge 2

The future deployment of the Square Kilometer Array (SKA) will lead to a massive increase in astronomical data which means that automatic detection and characterization of sources will be crucial for utilizing its full potential. We suggest how existing astronomical knowledge and tools can be utilized in a machine learning-based pipeline for finding 3D spectral line sources. We present a source-finding pipeline, designed to detect 21-cm emission from galaxies, that provided the second-best submission of SKA Science Data Challenge 2. The first pipeline step was galaxy segmentation, which consisted of a convolutional neural network (CNN) that took an HI cube as input and output a binary mask to separate galaxy and background voxels. The CNN was trained to output a target mask algorithmically constructed from the underlying source catalog of the simulation. For each source in the catalog, its listed properties were used to mask the voxels in its neighborhood that capture plausible signal distributions of the galaxy. To make the training more efficient, regions containing galaxies were oversampled compared to the background regions. In the following source characterization step, the final source catalog was generated by the merging and dilation modules of the existing source finding software SoFiA, and some complementary calculations, with the CNN-generated mask as input. To cope with the large size of HI cubes but also allow deployment on various computational resources, the pipeline was implemented with flexible and configurable memory usage. We show that once the segmentation CNN is trained, the performance can be fine-tuned by adjusting the parameters involved in producing the catalog from the mask. Different sets of parameter values give a trade-off between completeness and reliability

Speaker: Henrik Håkansson (Fraunhofer-Chalmers Centre for Industrial Mathematics)

5.hakansson utilizing convolutional.pdf

14:25 → 14:50 Coffe break

14:50 → 16:15 Talks: Afternoon session 2

Convener: Michael Lindqvist (Chalmers)

14:50 MeerKAT continuum/transient results

Speaker: Lindsay Magnus

15:15 Fundamental Physics with SKA

Radio telescopes can be used as detectors for gravitational waves (GWs) in both the low ($\sim$nHz) and high ($\gg$kHz) frequency regimes. These GWs provide a unique insight into, e.g., the physics at QCD phase transition, primordial black holes, or the nature of gravity. The upcoming SKA is expected to improve the constraints on GW background from existing radio telescopes.

Speaker: Yutong He (Stockholm University)

Yutong_He.pdf

15:30 Polarized intensity oddities in edge-on galaxies

SKA has superb wavelength coverage allowing us to map the dependence of polarized intensity on wavelength in all four quadrants of edge-on galaxies. Systematic differences between the two sides of the rotation axis, and also between north and south, are indicative of magnetic helicity of a certain sign. I will present theoretical plots showing the anticipated dependence for different models.

Speaker: Axel Brandenburg (Stockholm University)

3.Brandenburg.pdf

15:45 Spatially resolving the extended atmospheres of evolved stars with the SKA

The heavy mass-loss experienced by evolved asymptotic giant branch (AGB) stars provides metals and dust to the interstellar medium (ISM) from which new stars and planets will form. In our current understanding, mass loss occurs through dust-driven winds originating from the extended atmospheres of these stars. When the material has reached the cooler regions so that sufficient dust can form, radiation pressure accelerates the dust which drags the gas along the elements processed are injected in the AGB star are injected into the ISM. However, our understanding of the extended atmospheres of AGB stars is still poor. State-of-the-art simulations show that large convective cells play an important role, but recent observations at milliarcsecond resolution with ALMA have shown that the conditions in the extended atmospheres might be different than predicted by the models. Low-frequency Square Kilometer Array observations of evolved stars will make it possible to study the critical outer regions of the extended atmospheres where dust forms and is accelerated. With the high resolution and sensitivity of SKA, we can constrain atmospheric density and temperature structures at larger distances from the star. Also, simultaneous observations of SKA and ALMA will produce wide-range multi-wavelength data for various radii of the extended atmosphere, enabling us to test and constrain theoretical models in a way that was not possible before. With the fixed configuration and large field of view of SKA, we can study the temporal evolution of evolved star atmospheres and dust-forming regions. In this presentation, we will present these opportunities for the SKA to contribute in this field.

Speaker: Behzad Bojnordi Arbab (Chalmers University of Technology)

Behzad Bojnordi SKA meeting .pdf

16:00 Summary and next steps

Speaker: John Conway (Onsala Space Observatory, Chalmers University of Technology)

SKAmeet-summary-JCv2.pdf