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Jordan Tucker
What do you as part of DESI?
Within DESI I am studying the diversity of quasars and in particular dust-reddened quasars. I have a secondary target program that has been targeting reddened quasars that may have otherwise been missed by the nominal QSO selection. I am also a member of the ECS committee within DESI. The ECS committee organises monthly ECS meetings and plans pre-meeting ECS activities such as networking events and data tutorials.
What is the most interesting or exciting thing about DESI ?
I love being connected to people within the collaboration from all over the world. I have already learnt so much from being part of DESI and have met so many interesting people. In my work I enjoy exploring new datasets, trying to make connections and understanding new results. I particularly enjoy looking at different exotic quasar systems that DESI has been observing such as broad absorption line quasars and reddened quasars.
Any advice for an aspiring scientist?
Never give up and never think you are not good enough. Sometimes you might wonder whether there is an easier path than academia, but ask yourself if there is anything as enjoyable as exploring the Universe!
While spectroscopy is the standard method of measuring the redshift of luminous objects, it is a time-intensive technique, requiring, in some cases, hours of telescope time for a single source. Additionally, spectroscopy favours brighter objects, and therefore introduces an intrinsic bias towards luminous or closer sources. A simple method of estimating the redshift through photometry would prove invaluable to forthcoming surveys on the next generation of large radio telescopes, as well as alleviating the inherent bias towards the most optically bright sources. While there is a well-established correlation between the near-infrared K-band magnitude and redshift for galaxies, we find that the K-z relation breaks down for samples dominated by quasi-stellar objects (QSOs). Current methods of estimating photometric redshift rely either on template spectra, which requires a high number of infrared photometry points, or computationally intensive machine learning methods. Using photometric data from the Sloan Digital Sky Survey (SDSS) we investigate the relationship between combinations of magnitudes of a group of quasars, and their redshift. We find a high correlation between the colour relation (I-W2)/(W3-U) and redshift for a group of broad-line emission sources from the SDSS, and we conclude that this could be a robust estimator of the redshift.
The Parliamentary and Scientific Committee runs the event in collaboration with the Institute of Physics and other learned societies - the Royal Society of Chemistry, the Royal Academy of Engineering, Royal Society of Biology, Physiological Society, Council for the Mathematical Sciences, and the Nutrition Society.
For three years, as her PhD project, Vicky has been investigating quasars, their properties and how they may link in galaxy evolution. Quasars are astronomical objects, powered by gas, that spiral at very high velocities into extremely large black holes. They are found in the centres of some galaxies, and outshine the entire galaxy they sit in. Most appear very blue, but there are some that show much redder colours. By researching the properties of these red quasars, Vicky and her team have added weight to an emerging idea that red quasars are fundamentally different objects to blue quasars. The differences they have found could indicate that red quasars represent an important phase in galaxy evolution.
She presented her research to politicians and a panel of expert judges, as part of the annual poster competition, STEM for BRITAIN, on Thursday 4th March. After a weekend of deliberation, the winners were announced on Monday 8th March.
Unable to be in the Houses of Parliament this year, they all had to rise to the challenge of presenting their work remotely via an online platform, making the communication of already complex scientific concepts much more of a challenge.
"There are still many unanswered questions surrounding red quasars, such as whether black hole winds or radio jets are ultimately responsible for this enhanced radio emission," Victoria Fawcett, lead author of a new study on this finding and an astronomer at Newcastle University in the United Kingdom, said in a statement.
A quasar is the powerful central region of an active galaxy, and is driven by a supermassive black hole that is being fed huge amounts of matter. That matter forms a disk of gas around the black hole, known as an accretion disk, that reaches millions of degrees and releases fierce radiation winds. Meanwhile, magnetically collimated jets launch outwards from the disk.
Most quasars appear blue, a hue caused by optical and ultraviolet emissions from the hot accretion disk. However, a fraction appears red instead. To reach their conclusions about those red quasars, Fawcett and fellow researchers sampled approximately 35,000 quasars observed by DESI, the Dark Energy Spectroscopic Instrument on the Mayall Telescope at Kitt Peak National Observatory in Arizona.
The redness comes from the presence of dust, which absorbs shorter, bluer wavelengths but allows longer, redder wavelengths to pass. The red quasars must therefore be smothered in cosmic dust, formed of tiny grains just microns in size.
"It was really exciting to see the amazing quality of the DESI data and to discover thousands of these previously rare red quasars," Fawcett said. "I think this is the strongest evidence so far that red quasars are a key element in how galaxies evolve."
The red quasars seem to be radiating more strongly in radio waves than the blue quasars because of interactions between outflows of radiation pouring from a quasar and the surrounding curtains of dust. As the outflows slam into the dust, they excite molecules within the dust to prompt the emission of radio waves. Over time, the outflows, driven by the energy of a supermassive black hole hungrily feeding on vast amounts of matter, will blow the dusty cloak away to leave a naked blue quasar with much weaker radio emission. Fawcett calls this the 'blow-out' phase.
Keith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the University of Manchester. He's the author of \"The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence\" (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for a multitude of magazines and websites."}), " -0-10/js/authorBio.js"); } else console.error('%c FTE ','background: #9306F9; color: #ffffff','no lazy slice hydration function available'); Keith CooperSocial Links NavigationContributing writerKeith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the University of Manchester. He's the author of "The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence" (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for a multitude of magazines and websites.
This Hubble Space Telescope image (right) reveals the faint host galaxy that a bright quasar dwells within. The wealth of new detail in this picture helps solve a three-decade old mystery about the true nature of quasars, the most distant and energetic objects in the universe.
The HST image shows clearly that the quasar, called 1229+204, lies in the core of a galaxy that has a common shape consisting of two spiral arms of stars connected by a bar-like feature. The host galaxy is in a spectacular collision with a dwarf galaxy. The collision apparently fuels the quasar "engine" at the galaxy center - presumably a massive black hole - and also triggers many sites of new star-formation.
The image is one of a pair of relatively nearby quasars that were selected as early targets to test the resolution and dynamic range of HST's newly-installed Wide Field and Planetary Camera, which contains special optics to correct for a flaw in Hubble's primary mirror. The observations were made by Dr. John Hutchings of Dominion Astrophysical Observatory in Victoria, British Columbia. "The project was impossible from ground-based telescopes," says Dr. Hutchings, who has been researching quasars for many years. " The sharpness of the Hubble pictures is leading to major new discoveries almost anywhere you point it in the sky."
Quasars are the most distant objects in the universe, and so are among the earliest objects known to have formed in the young universe, more than 12 billion years ago. The most widely accepted notion is that quasars are in galaxies with active, supermassive black holes at their centers. However, because of their enormous distance, the `host' galaxies appear very small and faint, and are very hard to see against the much brighter quasar light at the center. Though a quasar might no be much larger than our solar system it releases as much energy as billions of stars.
Though a previous ground based observation using the Canada-France-Hawaii Telescope (at 0.5 arcsec resolution) first identified the barred spiral galaxy in 1229+204, Hubble shows clearly the galaxy's structure and reveals details of the collision.
Hubble reveals that an extended blue feature on one side of the galaxy is really a string of knots, which are probably massive young star clusters. The star clusters were most likely formed as a result of a collision between the host galaxy and a small gas-rich companion. HST also reveals shell-like structures along the bar that might be produced by gravitational tidal resonance forces between the spiral and its companion.
An important fraction of quasars are red at optical wavelengths, indicating (in the vast majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In recent work by our group, we have shown fundamental differences in the radio properties of SDSS optically selected red quasars, which cannot be explained with a simple viewing angle hypothesis (Klindt et al. 2019, Fawcett et al. 2020, Rosario et al. 2020, Rosario et al. 2021). In our latest work, we use VLT/X-shooter spectroscopy of a sample of red and typical quasars to gain insight into these differences. We confirm that dust reddening is the main cause of the red colours and explore the emission line properties of our sample. We confront our spectra against accretion disc models and confirm that red quasars are powered by standard thin-disc accretion, finding tentative evidence that red quasars have higher Eddington ratios for any given black hole mass. These results suggest that dusty winds could be driving the fundamental differences in red quasars, and so they may represent an important phase in galaxy evolution. Using DESI spectra, we can now push to more extinguished, lower luminosity systems, which will test whether these results extend to more extreme reddened systems.
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