Noticias emocionantes sobre SKAO: First on-sky spectrum of HI obtained with an SKA-Mid dish and 10000 SKA-Low antennas!

[Theresa Wiegert]

Hi everyone! 

In case you missed it: There is some exciting news from the SKAO construction: End of July, one of the SKA-Mid antennas made a first detection of the neutral hydrogen (HI) line! 

As well, SKA-Low now consists of 10 000 antennas (I.e. about 1/13th of the finished array)!

See more details below, from the SKAO Chief scientist Naomi McClure-Griffiths: 

¡Hola a todos!

Tenemos noticias emocionantes sobre la construcción de SKAO: ¡A finales de julio, una de las antenas de SKA-Mid detectó por primera vez la línea de hidrógeno neutro (HI)!

Además, SKA-Low ahora cuenta con 10 000 antenas (es decir, aproximadamente 1/13 del conjunto terminado).

Vean más detalles a continuación, de la Chief Scientist de SKAO, Naomi McClure-Griffiths:

Un saludo, 

Theresa, for the Spanish SKAO coordination team

Begin forwarded message:

From: "McClure-Griffiths, Naomi" <Naomi.McClu...@skao.int>

Subject: News: First on-sky spectrum of HI obtained with an SKA-Mid dish plus bonus news

Date: 21 August 2025 at 05:19:26 GMT-4

To: swg-all <swg...@skao.int>

Dear Colleagues,

 

We are pleased to share with you the first on-sky spectrum obtained with an SKA-Mid dish. 

 

On 25 July 2025, with the SKA001 dish in its stow position (pointing at the Zenith), a series of drift scans (auto-correlation mode) were obtained using the Band 2 receiver (950-1760 MHz). These scans were controlled by the telescope monitor and control (TMC) and fed through the entire SKA-Mid signal chain. The scans were processed through the SKA-Mid demonstrator correlator, and the processed signals ingested by the Science Data Processor (SDP) to produce CASA Measurement Set format datasets (MSv2).

 

The full polarisation correlations are shown below (flux scale is arbitrary units):

The clear signal of Galactic HI is seen in the XX and YY spectra (as indicated in the figure).  We can also see plenty of RFI, distinguished because it is visible in all four Stokes spectra.  Thankfully, these signals will be much less visible in interferometric mode.  

 

From the drift scans a series of spectra around the HI line have been extracted and the line profiles placed on the VLSR scale. Good agreement in spectral shape is seen with spectra from the Leiden/Argentine/Bonn LAB) HI survey from the expected Zenith (I,b) at the time of the observations.    Three examples are shown below:

These first tests also included a measurement of the system temperature, which confirmed that the system temperature is ~15 K as expected!

This is a fantastic result and marks a key milestone in the life of SKA-Mid. It is an important step on the path to achieving the goal of obtaining first fringes using 3 SKA-Mid dishes by the end of this year.  Congratulations to the Mid team for passing this milestone!   

(And as some last-minute bonus news about Low: the 10,000th antenna has just been installed!)

Regards,

Naomi 

		Prof Naomi McClure-Griffiths FAA Chief Scientist SKAO naomi.mcclu...@skao.int +61 482 715 176 www.skao.int SKA Observatory Jodrell Bank, Lower Withington, Macclesfield, SK11 9FT, UK Australian National University Canberra ACT 2611 Australia

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~~~

Theresa Wiegert, PhD

SKAO science community liaison/researcher

Instituto de Astrofísica de Andalucía (IAA-CSIC)

Address: Glorieta de la Astronomía s/n 18008, Granada, Spain

Email: twie...@iaa.es

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