Search Publications
Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code - III. ω Cen
Brownstein, Joel R.; Cunha, Katia; Smith, Verne V. +18 more
We study the multiple populations of ω Cen by using the abundances of Fe, C, N, O, Mg, Al, Si, K, Ca, and Ce from the high-resolution, high signal-to-noise (S/N > 70) spectra of 982 red giant stars observed by the SDSS-IV/APOGEE-2 survey. We find that the shape of the Al-Mg and N-C anticorrelations changes as a function of metallicity, continuo…
Location and energetics of the ultra-fast outflow in PG 1448+273
Piconcelli, E.; Tombesi, F.; Middei, R. +3 more
Context. Ultra-fast outflows (UFOs) are the most powerful disk-driven winds in active galactic nuclei (AGNs). Theoretical and observational evidence shows that UFOs play a key role in the AGN feedback mechanism. The mechanical power of the strongest UFOs may be enough to propagate the feedback to the host galaxies and ultimately shape the AGN-gala…
X-ray-induced chemistry of water and related molecules in low-mass protostellar envelopes
Walsh, Catherine; Bosman, Arthur D.; Nomura, Hideko +2 more
Context. Water is a key molecule in star- and planet-forming regions. Recent water line observations toward several low-mass protostars suggest low water gas fractional abundances (<10−6 with respect to total hydrogen density) in the inner warm envelopes (r < 102 au). Water destruction by X-rays is thought to influence …
The Flattening Metallicity Gradient in the Milky Way's Thin Disk
Shen, Juntai; Li, Zhao-Yu; Vickers, John J.
We calculate the ages, orbits and phase-space coordinates for a sample of ~4 million LAMOST and Gaia stars. The ages are cross-matched and compared with values from two other popular age catalogs, which derive the ages using different methods. Of these ~4 million stars, we select a sample of 1.3 million stars and investigate their radial metallici…
The dynamics of the globular cluster NGC 3201 out to the Jacobi radius
Lewis, Geraint F.; de Boer, Thomas; Mackey, Dougal +7 more
As part of a chemodynamical survey of five nearby globular clusters with 2dF/AAOmega on the Anglo-Australian Telescope (AAT), we have obtained kinematic information for the globular cluster NGC 3201. Our new observations confirm the presence of a significant velocity gradient across the cluster which can almost entirely be explained by the high pr…
APOGEE discovery of a chemically atypical star disrupted from NGC 6723 and captured by the Milky Way bulge
Piatti, Andrés E.; Beers, Timothy C.; Placco, Vinicius M. +26 more
The central (`bulge') region of the Milky Way is teeming with a significant fraction of mildly metal-deficient stars with atmospheres that are strongly enriched in cyanogen (12C14N). Some of these objects, which are also known as nitrogen-enhanced stars, are hypothesised to be relics of the ancient assembly history of the Mil…
The first simultaneous X-ray broadband view of Mrk 110 with XMM-Newton and NuSTAR
Grosso, N.; Porquet, D.; Reeves, J. N. +2 more
Context. Soft and hard X-ray excesses, compared to the continuum power-law shape between ∼2−10 keV, are common features observed in the spectra of active galactic nuclei (AGN) and are associated with the accretion disc-corona system around the supermassive black hole. However, the dominant process at work is still highly debated and has been propo…
New Evidence for Extended He I> Reionization at z ≳ 3.5 from He II Lyman Alpha and Beta Transmission Spikes
Richter, Philipp; Hennawi, Joseph F.; Worseck, Gábor +3 more
We present new high-resolution (R = λ/Δλ ∼ 14,000) spectra of the two brightest He II-transparent quasars in the far-UV at zem > 3.5, HE2QS J2311-1417 (zem = 3.70) and HE2QS J1630+0435 (zem = 3.81), obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. In the predominantly saturated He II …
Metallicity Estimation of RR Lyrae Stars From Their I-Band Light Curves
Grebel, Eva K.; Pojmański, Grzegorz; Dékány, István
We have revisited the problem of metallicity prediction of RR Lyrae stars from their near-infrared light curves in the Cousins I wave band. Our study is based on high-quality time series photometry and state-of-the-art high-resolution spectroscopic abundance measurements of 80 fundamental-mode (RRab) and 24 first-overtone (RRc) stars, spanning ~[-…
The Nature of the Milky Way's Stellar Halo Revealed by the Three Integrals of Motion
Carollo, Daniela; Chiba, Masashi
We developed a new selection method of halo stars in the phase-space distribution defined by the three integrals of motion in an axisymmetric Galactic potential (E, Lz, I3), where I3 is the third integral of motion. The method is used to explore the general chemodynamical structure of the halo based on stellar samp…