ASTRON/JIVE Daily Image

Jan Noordam turns 65 and is appointed Resident Visionary

Tom Oosterloo — Sun, 13 May 2012 00:00:00 GMT

Today, May 13 2012, Jan Noordam reaches the respectable age of 65. Birthdays normally are reasons for celebration, although for some people reaching the particular milestone of 65 is more complex because with it comes retirement, the end of the active working career and other complicated changes in life. Jan, however, does not have this problem. Instead of stop working and leaving Astron, today is the start of the highpoint of his working life because Jan will continue his career at Astron as Resident Visionary, a title everybody will understand he is very proud of.

This appointment is the recognition of his many important contributions, over a period of 37 years, to the discussions at Astron. In many of the wonderful projects Astron has undertaken over the years, Jan's input has been important and, in particular, very original. This last is because Jan's horizon (in space but also in time) is much broader than that of most people so Jan has a better view of things to come.

To celebrate Jan's 65 birthday, to underline his many contributions to Astron and astronomy, and to mark the start of his new position, on June 15 (1300-1800) we are organizing a Mini-Symposium at Astron. A program with speakers will be announced next week via the Astron homepage and the daily image.

By the way, if one would measure impact by sheer numbers, Jan's most important contribution has been his instigation of the Astron/Jive Picture of the Day (AJPOD). About 6 years ago, Jan suggested we display a daily web-window on Astron, showing all aspects of the organization, on the science, but also about the normal life at Astron and other things. At the time, nobody (except Jan of course) believed it would last long, but Jan's Visionary capabilities turned out to be right. Six years later the AJPODs are still going strong. Over the years, daily images have been looked at about 2,000,000 (two million!!!) times in total, by about 50,000 (fifty thousand!!!!) different people from more than 100 countries. Most people know Astron because of the AJPODs!!!

Girlsday 2012

Diversity Committee — Mon, 14 May 2012 00:00:00 GMT

On 26 April ASTRON, JIVE and the NOVA-ASTRON Optical Infrared Instrumentation group hosted 32 young women from local schools as part of Girlsday 2012.

Our visitors heard presentations on radio astronomy and R&D, and participated in four hands-on workshops. These included live chatting with professional female astronomers about their lives and work, measuring signals from a local radio transmitter (while dodging rain showers), listening to a pulsar with the Dwingeloo telescope, exploring Doppler effect (again dodging rain), and soldering LED packets.

In their feedback questionnaires many of the girls enjoyed the activities ("cool", "really cool" and "super cool") and talks ("difficult but fascinating"). Most also said that they now think more favorably about studies in science or technology. Other things they learned: not all scientists wear lab coats; astronomers often sit behind computers; and there are lots of foreigners and not many women. Clearly next year, according to feedback surveys, we will also need to pray more fervently to the rain gods not to impinge on our outdoor activities!

Girlsday is a European initiative aimed at stimulating girls' interest in science, technology and ICT, and takes place annually in April. This is the fifth Girlsday for ASTRON/JIVE and was organised by the Diversity Committee. More information about Girlsday in the Netherlands can be found at www.girlsday.nl.

Colloquium: 'The ionized Galactic disk - Radio Recombination Line survey at 1.4 GHz with HIPASS'

Marta Alves (Institut d'Astrophysique Spatiale, Paris) — Tue, 15 May 2012 00:00:00 GMT

Radio Recombination Lines (RRLs) have been widely used to detect and catalogue HII regions, which trace current formation of massive stars. The diffuse electron gas along the Galactic plane is also of intrinsic interest. Its detection complements the data available from catalogues of HII regions and more importantly it helps to answer open questions on the relationship between the narrow and the thick components of the Warm Ionized Medium, namely the filling factor and the transport of the ionizing radiation from the hot stars to the broad distribution.

I use three RRLs at 1.4 GHz from the Parkes All-Sky Survey and associated Zone of Avoidance Survey to map the diffuse ionized gas within 4 degrees of the Galactic plane, between longitudes of 20 to 44 degrees, at 14.8 arcmin resolution. This is the first fully-sampled map of RRL emission giving the first unambiguous free-free emission map in this region.

The electron temperature (Te) distribution of the ionized gas in the area under study is derived using the line and continuum data from the same survey. It is found that the diffuse medium has similar Te to that of the individual HII regions, with a mean value of 6000 K in the Galactic plane.

Subtraction of the free-free component from the total continuum leads to the first direct measurement of the synchrotron emission at 1.4 GHz; its latitude distribution shows a narrow component of width 2 degrees.

I also produce lists of HII regions and Supernova Remnants (SNRs) using the thermal and non-thermal maps, where I confirm the synchrotron nature of two proposed SNRs by Kaplan et al. and the SNR G35.6-0.4 recently re-identified by Green.

Little monsters: An active galactic nucleus in a dwarf starburst galaxy

Adam Deller — Wed, 16 May 2012 00:00:00 GMT

Active Galactic Nuclei (AGN) are amongst the most energetic objects in the Universe. Their phenomenal energy output is powered by the accretion of matter onto supermassive black holes - hungry beasts with a mass of millions, or even billions of times greater than that of the Sun. The intense radiation and strong winds which they produce can radically change the evolution of their host galaxies over cosmological time, repainting the landscape of structure we see in the modern Universe. The most massive AGN are typically the brightest and most spectacular, but "little monsters" - AGN powered by relatively lightweight black holes around a million times the Sun's mass or less - also dominate their surroundings and can furthermore provide important clues about the origin of supermassive black holes in the early Universe.

Henize 2-10 is a relatively nearby (9 Mpc) dwarf irregular galaxy undergoing an intense burst of star formation, as shown by the larger composite image above (purple=x-ray [Chandra], yellow=radio [VLA], red/green/blue=optical [Hubble]). In 2011, Reines et al. (Nature, 470, 66) showed that Henize 2-10 also hosts a probable "little monster" - a supermassive black hole of around a million solar masses. This little monster is relatively bright in radio and hard x-rays compared to the optical and near infrared emission, as can be seen by in the inset picture that shows radio emission from the VLA and near-infrared Paschen alpha emission observed with Hubble. Recently, the evidence for this AGN interpretation has been strengthened by a detection of the radio emission using the Long Baseline Array (LBA) in Australia, using an eVLBI observation at high data rate (1 Gbps per station). The LBA detection is shown in green in the inset image. The high angular resolution of the LBA confirms that the radio source is very compact (approximately 1 parsec in size), just as one would expect for a radio AGN. These results have recently been published in a letter to the Astrophysical Journal (http://adsabs.harvard.edu/abs/2012ApJ...750L..24R).

Girlsday Artwork

Roy Smits — Thu, 17 May 2012 00:00:00 GMT

Following up on the recent daily image (14 May), today we present the wonderful artwork that the Girlsday-Girls have produced as part of Girlsday 2012.

One of the "cool" activities was live chatting (via Skype) with a professional female astronomer. All questions were allowed; from work to hobbies to even more personal details. Part of the assignment was to draw their findings onto an A3-paper. To accomplish this, the girls worked in pairs and produced some magnificent artwork as can be seen in the collage.

A winner was declared in each of the categories "Best Artwork" and "Most Informative". The winning artwork is shown as the large images.

Many thanks to all the Girlsday-Girls and the female astronomers who volunteered to answer all the girl's questions to make this event so very successful!

More information about Girlsday in the Netherlands can be found at http://www.girlsday.nl