Quasars & Active Galaxies

Bin Luo

We are very pleased to welcome Bin Luo as a guest blogger today. He led the study on supermassive black holes that is the subject of our latest press release. Bin obtained a PhD degree in Astronomy and Astrophysics from the Pennsylvania State University in 2010, working on the Chandra Deep Field surveys. He then worked as a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, and later back at the Pennsylvania State University. He will start a faculty position in September 2015 at the Nanjing University in China. Bin has mainly been working on X-ray studies of supermassive black holes in the centers of galaxies. He is now leading the data analysis of the 7-million-second (81 days) Chandra Deep Field-South survey, the deepest Chandra observation ever performed.

I have been studying the X-ray emission from accreting supermassive black holes since I was a graduate student. These monstrous black holes – quasars fueled by large amounts of gas and dust, consuming of the order of a couple solar masses per year – are known nearly universally to be strong X-ray emitters. Meanwhile, strong line emission – that is, light coming from a narrow range of wavelengths – is also a hallmark of quasar spectra in optical and ultraviolet bands. Therefore, I was quite puzzled when we discovered that a small group of quasars with remarkably weak ultraviolet line emission are often extremely X-ray weak. The pioneering work was led by Jianfeng Wu, Niel Brandt, and Pat Hall in 2011 and 2012, where the X-ray emission from 19 such quasars was examined. What makes things even more interesting is that for a subgroup of these quasars selected with refined ultraviolet properties, almost 100% are weak in X-ray light.

Astronomers have studied 51 quasars with NASA's Chandra X-ray Observatory and found they may represent an unusual population of black holes that consume excessive amounts of matter, as described in our latest press release. Quasars are objects that have supermassive black holes that also shine very brightly in different types of light. By examining the X-ray properties with Chandra, and combining them with data from ultraviolet and visible light observations, scientists are trying to determine exactly how these large black holes grow so quickly in the early Universe.

Today we released six new images from Chandra’s vast data archive. Each one of these astronomical images combines X-rays from Chandra with data from telescopes that detect different types of light such as infrared, radio, and visible light.

Every year, NASA's Chandra X-ray Observatory looks at hundreds of objects throughout space to help expand our understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive, an electronic repository that provides access to these unique X-ray findings for anyone who would like to explore them. With the passing of Chandra's 15th anniversary in operation on August 26, 1999, the archive continues to grow as each successive year adds to the enormous and invaluable dataset.

Multiple images of a distant quasar are visible in this combined view from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The Chandra data, along with data from ESA's XMM-Newton, were used to directly measure the spin of the supermassive black hole powering this quasar. This is the most distant black hole where such a measurement has been made, as reported in our press release.

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming.

This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA's Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF's Very Large Array (pink).

Teddy Cheung, Credit: Craig Walker

We are delighted to welcome Teddy Cheung, from the National Academy of Sciences, and resident at the Naval Research Laboratory in Washington DC, to give a guest blog post today. Teddy is first author of a paper describing the discovery of the most distant X-ray jet detected to date. Here, he explains some of the background story behind this discovery.

When I started graduate school in 1999 at Brandeis University, exciting discoveries were being made down the road in Cambridge, Massachusetts, with the then newly launched Chandra X-ray Observatory. The first Chandra image unexpectedly revealed a bright X-ray jet from a distant quasar (http://chandra.harvard.edu/press/99_releases/press_082399.html) and the research groups at SAO and MIT were puzzling over it. But it took me leaving Boston to find my eventual connection.

I spent the summer of 2000 at the Space Telescope Science Institute in Baltimore, Maryland, wanting to learn something entirely new and took on a project in Meg Urry's group studying the galaxies of BL Lac objects (a type of cousin to the quasars) using ground-based near-infrared data. Coincidentally, I shared an office with another graduate student working with Dr. Urry for the summer, Fabrizio Tavecchio from Italy, and they were at that time puzzling over the same Chandra jet detection. Little did I appreciate at the time, that this visit to Baltimore would lead back to my eventual PhD project at Brandeis on the Chandra quasar jets.

This composite image shows the most distant X-ray jet ever observed. X-ray data from NASA's Chandra X-ray Observatory are shown in blue, radio data from the NSF's Very Large Array are shown in purple and optical data from NASA's Hubble Space Telescope are shown in yellow. The jet was produced by a quasar named GB 1428+4217, or GB 1428 for short, and is located 12.4 billion light years from Earth. Labels for the quasar and jet can be seen by mousing over the image. The shape of the jet is very similar in the X-ray and radio data.