Search Publications
Keck Spectroscopy of Faint 3 < z < 8 Lyman Break Galaxies: Evidence for a Declining Fraction of Emission Line Sources in the Redshift Range 6 < z < 8
Richard, Johan; Stark, Daniel P.; Ellis, Richard S. +5 more
Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with the Wide Field Camera 3 on board the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star-forming galaxies with detectable Lyman alpha (Lyα) emission in the redshift range 6.3 < z < 8.8. Our…
What Turns Galaxies Off? The Different Morphologies of Star-forming and Quiescent Galaxies since z ~ 2 from CANDELS
Papovich, Casey; Bell, Eric F.; Giavalisco, Mauro +21 more
We use HST/WFC3 imaging from the CANDELS Multi-Cycle Treasury Survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses >3 × 1010 M ⊙ from z = 2.2 to the present epoch, a time span of 10 Gyr. We explore the relationship between rest-frame optic…
The Characteristic Star Formation Histories of Galaxies at Redshifts z ~ 2-7
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +3 more
A large sample of spectroscopically confirmed star-forming galaxies at redshifts 1.4 <= z spec <= 3.7, with complementary imaging in the near- and mid-IR from the ground and from the Hubble Space Telescope and Spitzer Space Telescope, is used to infer the average star formation histories (SFHs) of typical galaxies from z ~ 2 to 7.…
Lower-luminosity Galaxies Could Reionize the Universe: Very Steep Faint-end Slopes to the UV Luminosity Functions at z >= 5-8 from the HUDF09 WFC3/IR Observations
Trenti, M.; Oesch, P. A.; Carollo, C. M. +7 more
The HUDF09 data are the deepest near-IR observations ever, reaching to 29.5 mag. Luminosity functions (LFs) from these new HUDF09 data for 132 z ~ 7 and z ~ 8 galaxies are combined with new LFs for z ~ 5-6 galaxies and the earlier z ~ 4 LF to reach to very faint limits (<0.05 L* z = 3). The faint-end slopes α are steep: -1.79 ± 0.12 …
Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we…
Identification of Kinetic Alfvén Wave Turbulence in the Solar Wind
Bale, S. D.; Chen, C. H. K.; Mozer, F. S. +4 more
The nature of small-scale turbulent fluctuations in the solar wind is investigated using a comparison of Cluster magnetic and electric field measurements to predictions arising from models consisting of either kinetic Alfvén waves or whistler waves. The electric and magnetic field properties of these waves from linear theory are used to construct …
The intense starburst HDF 850.1 in a galaxy overdensity at z ≈ 5.2 in the Hubble Deep Field
Carilli, Chris; Dickinson, Mark; Ellis, Richard +24 more
The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time. An early map of the Hubble Deep Field at a wavelength of 850 micrometres, which is sensitive to dust emission powered by star formation, revealed the brightest source in …
The mean star formation rate of X-ray selected active galaxies and its evolution from z ~ 2.5: results from PEP-Herschel
Berta, S.; Magnelli, B.; Nordon, R. +37 more
We study relationships between star-formation rate (SFR) and the accretion luminosity and nuclear obscuration of X-ray selected active galactic nuclei (AGNs) using a combination of deep far-infrared (FIR) and X-ray data in three key extragalactic survey fields (GOODS-South, GOODS-North and COSMOS), as part of the PACS Evolutionary Probe (PEP) prog…
Multiple Stellar Populations in 47 Tucanae
Di Criscienzo, M.; Anderson, J.; Milone, A. P. +16 more
We use Hubble Space Telescope (HST) and ground-based imaging to study the multiple populations of 47 Tucanae (47 Tuc), combining high-precision photometry with calculations of synthetic spectra. Using filters covering a wide range of wavelengths, our HST photometry splits the main sequence into two branches, and we find that this duality is repeat…
A simplified view of blazars: clearing the fog around long-standing selection effects
D'Elia, V.; Polenta, G.; Giommi, P. +3 more
We propose a scenario where blazars are classified into flat-spectrum radio quasars (FSRQs), BL Lacertae (BL Lac) objects, low-synchrotron, or high-synchrotron peaked objects according to a varying mix of the Doppler-boosted radiation from the jet, the emission from the accretion disc, the broad-line region, and the light from the host galaxy. In …