Research Interests

  • The Intergalactic Medium at High Redshifts and the Epoch of Reionization
  • Quasar and Galaxy Evolution, Quasar Lifetimes, and Black Hole Formation Models
  • Structure and Dynamics of the Milky Way
  • Machine Learning and Data-Driven Models
  • Current Research Projects

    Constraints on Quasar Lifetimes from Proximity Zone Measurements

    The lifetime of quasars is one of the most fundamental quantities for understanding black hole formation and quasar evolution, but yet it remains uncertain by several orders of magnitude. Quasar lifetimes can be constrained by measuring the sizes of their proximity zones, which is the region of enhanced transmitted flux around the quasar due to its own ionizing radiation. By analyzing a new data set of 34 medium resolution spectra at redshift 5.8 ≤ z ≤ 6.5 we identified a new population of quasars with very small proximity zones, indicating quasar lifetimes of less than 100,000 years. These objects pose a significant challenge to current black hole formation models, which require lifetimes of the order of the Hubble time to grow the observed supermassive black holes in the center of these quasars. For more information please have a look at our paper and at the press release.

    First Spectroscopic Study of a Young Quasar

    The presence of young quasars in the early Universe poses an interesting challenge for current models of the growth and formation of supermassive black holes, and puts stringent constraints on quasar and galaxy evolution theories. We conduct the first comprehensive spectroscopic study of the youngest quasar known, SDSS J1335+3533 at z=5.9012, whose lifetime we estimate to be less than 10,000 years. Deep optical and near-infrared spectra allow us to measure the mass of the central black hole, the Eddington ratio, and its bolometric luminosity, which are consistent with properties of other co-eval quasar of similar luminosity. The only possible anomaly associated with youth are its weak emission lines, but larger samples are needed to shed light on a potential causal connection. We discuss the implications of short quasar lifetimes for various black hole growth scenarios, and argue that future observations of young quasars with JWST could distinguish between them. For details please have a look at our paper.

    The Opacity of the Intergalactic Medium and its Implications for the Epoch of Reionization

    Determining when and how the epoch of reionization proceeded is one of the major goals of observational cosmology today. During this early evolutionary phase of our universe, the cosmic “dark ages” following recombination ended, and the intergalactic medium (IGM) transitioned from a neutral state into the ionized medium that we observe today due to the ultraviolet radiation of the first stars, galaxies and quasars. The details of the reionization process not only reflect the nature of these primordial objects, but also the formation of large scale structure and are therefore a subject of major interest. We presented new measurements of the evolution of the mean opacity of the IGM within the Lyman-alpha forest between 4.8 ≲ z ≲ 6.3, which provides constraints about the timing of the reionization process as well as its morphology. We compare our measurements to hydrodynamical simulations with a fluctuating ultraviolett background and a fluctuating temperature field and find good agreement between the observations and the simulations. More information can be found in our paper. The data set used for this project is publicly available.

    Spectrophotometric Distances to Luminous Red Giant Stars

    With contemporary infrared spectroscopic surveys like APOGEE, red-giant stars can be observed to distances and extinctions at which Gaia parallaxes are not highly informative. Here we employ a linear combination of APOGEE spectral pixel intensities and multi-band photometry from Gaia, 2MASS, and WISE to predict parallaxes spectrophotometrically, using a data-driven model for 45,000 red-giant branch stars that are more luminous than the red clump. We obtain distance estimates with 10% uncertainties out to heliocentric distances of 20 kpc, which enables us to make global maps of the Milky Way’s disk. For more information, please check out our paper. Our predicted spectrophotometric parallaxes are available here.

    The Circular Velocity Curve of the Milky Way out to 25 kpc

    The circular velocity of the Milky Way and in particular its value at the sun's Galactocentric radius, provide important constraints on the mass distribution of our Galaxy and the local dark matter density. The latter is crucial for interpreting and analyzing any direct as well as indirect detection experiments of dark matter. The local circular velocity at the sun's location plays an important role when placing the Milky Way in a cosmological context and asking for instance, whether it falls onto the Tully-Fisher relation. Assuming an axisymmetric gravitational potential of the Milky Way we measure its circular velocity by means of Jeans modeling out to a Galactocentric distance of 25 kpc with more than 23,000 luminous red giant stars as a tracer population. We find that the circular velocity curve is gently declining with a very shallow derivative. For more information, please have a look at our paper.

    Publications

    first & second author

  • Eilers et al. 2019 (ApJ, 871, 120): The Circular Velocity Curve of the Milky Way from 5 to 25 kpc
  • Hogg, Eilers & Rix 2019 (ApJ, subm.): Spectrophotometric parallaxes with linear models: Accurate distances for luminous red-giant stars
  • Eilers et al. 2018b (ApJ, 867, 30): First Spectroscopic Study of a Young Quasar
  • Eilers et al. 2018a (ApJ, 864, 53): The Opacity of the Intergalactic Medium Measured Along Quasar Sightlines at z~6
  • Eilers et al. 2017b (ApJ, 844, 136): Joint Bayesian Estimation of Quasar Continua and the Lyman-Alpha Forest Flux Probability Distribution Function
  • Eilers et al. 2017a (ApJ, 840, 24): Implications of z~6 Quasar Proximity Zones for the Epoch of Reionization and Quasar Lifetimes. Link to the press release.
  • De Bruijne & Eilers 2012 (A&A, 546, 61): Radial velocities for the Hipparcos-Gaia Hundred-Thousand-Proper-Motion project

  • co-author

  • Kakiichi et al. 2018 (MNRAS, 479, 43): The Role of Galaxies and AGN in Reionising the IGM - I: Keck Spectroscopy of 5 < z < 7 Galaxies in the QSO Field J1148+5251
  • El-Badry et al. 2018 (MNRAS, 473, 5043): Signatures of Unresolved Binaries in Stellar Spectra: Implications for Spectral Fitting
  • Davies et al. 2018 (ApJ, 855, 106): A New Method to Measure the Post-Reionization Ionizing Background from the Joint Distribution of Lyman-alpha and Lyman-beta Forest Transmission
  • Mazzucchelli et al. 2017 (ApJ, 849, 91): Physical Properties of 15 Quasars at z>6.5
  • Lee et al. 2014 (ApJL, 795, 12): Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2
  • Link to ADS.

    Image Credit: NASA/ESA/STScI

    Curriculum Vitae

    Education

    2015-present: Graduate student at the Max-Planck Institute for Astronomy in Heidelberg
    2012-2015: Master of Science in Physics at the University of Heidelberg
    2008-2011: Bachelor of Science in Physics at the University of Göttingen

    Invited Talks & Seminars

    Oct. 2018: ITC Luncheon, Harvard-Smithsonian Center for Astrophysics
    Oct. 2018: Brown Bag Lunch Series, Massachusetts Institute of Technology
    Oct. 2018: High Energy Astrophysics Seminar, University of Michigan
    Sept. 2018: Revealing Cosmology and Reionization History with the Intergalactic Medium, Kavli IPMU, Tokyo
    May 2018: Astro Lunch, University of Washington
    Feb. 2018: Cosmology Seminar, UC Berkeley
    Feb. 2018: Cosmology Seminar, KIPAC Stanford
    Feb. 2018: Astro Lunch, UC Santa Barbara

    Honours & Fellowships

    2019: NASA Hubble Fellowship
    2019: Pappalardo Fellowship, Massachusetts Institute of Technology
    2015-2019: Fellow of the International Max Planck Research School
    2016-2018: PhD Fellowship of the German National Academic Foundation
    2017: Ernst Patzer Award
    2016: Max Planck Fellow for the Lindau Nobel Laureate Meeting
    2012-2015: Scholarship of the German National Academic Foundation

    Full CV.

    Image Credit: NASA/STScI

    Outreach

    I work as an Outreach Fellow at the "Haus der Astronomie" - Center for Astronomy Education and Outreach (HdA), where we show groups of visitors of all ages and academic backgrounds our planetarium and the telescopes, guide them through the Max Planck Institute for Astronomy and the outreach center, and explain the astronomical research that is conducted in Heidelberg.

    I have written a couple of articles (about the growth of black holes and a new map of the Milky Way) for a German astronomy magazine for amateur astronomers called Sterne und Weltraum.

    There is also an article about my work on IFLScience and a post (in German) on the blog of the Lindau Nobel Laureate Meetings.

    Travel

    Whenever I'm not busy doing astronomy, I love to travel around the world, discover remote places, meet people and explore different cultures. Here are some impressions of my recent adventures.

    Contact

    Max Planck Institute for Astronomy
    Königstuhl 17
    69117 Heidelberg
    Germany

    Email: eilers(at)mpia.de
    Phone: +49 (0)6221-528 488