We present trigonometric parallax and proper motion measurements toward 22 GHz water and 6.7 GHz methanol masers in 16 high-mass star-forming regions. These sources are all located in the Scutum... Show moreWe present trigonometric parallax and proper motion measurements toward 22 GHz water and 6.7 GHz methanol masers in 16 high-mass star-forming regions. These sources are all located in the Scutum spiral arm of the Milky Way. The observations were conducted as part of the Bar and Spiral Structure Legacy (BeSSeL) survey. A combination of 14 sources from a forthcoming study and 14 sources from the literature, we now have a sample of 44 sources in the Scutum spiral arm, covering a Galactic longitude range from 0° to 33°. A group of 16 sources shows large peculiar motions of which 13 are oriented toward the inner Galaxy. A likely explanation for these high peculiar motions is the combined gravitational potential of the spiral arm and the Galactic bar. Show less
Keppler, M.; Teague, R.; Bae, J.; Benisty, M.; Henning, T.; Boekel, R. van; ... ; Semenov, D. 2019
Deep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z similar to 2-4.5. Here we combine... Show moreDeep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z similar to 2-4.5. Here we combine VLT /MUSE Guaranteed Time Observations of the Hubble Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other publicly available data from VLT /VIMOS and VLT /FORS2 to construct a catalogue of He II lambda 1640 emitters at z greater than or similar to 2. The deepest areas of our MUSE pointings reach a 3 sigma line flux limit of 3.1 x 10(19) erg s(-1) cm(-2). After discarding broad-line active galactic nuclei, we find 13 He II lambda 1640 detections from MUSE with a median M-UV = -20.1 and 21 tentative He II lambda 1640 detections from other public surveys. Excluding Ly alpha, all except two galaxies in our sample show at least one other rest-UV emission line, with C III] lambda 1907, lambda 1909 being the most prominent. We use multi-wavelength data available in the Hubble legacy fields to derive basic galaxy properties of our sample through spectral energy distribution fitting techniques. Taking advantage of the high-quality spectra obtained by MUSE (similar to 10-30 h of exposure time per pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics of the He II lambda 1640 emitters. Line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. Even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame He II lambda 1640 equivalent widths (similar to 0.2-10 angstrom), thus additional mechanisms are necessary in models to match the observed He II lambda 1640 properties. Show less
Gasperin, F. de; Dijkema, T.J.; Drabent, A.; Mevius, M.; Rafferty, D.; Weeren, R.J. van; ... ; Williams, W. 2019
Context. The direct detection and characterization of planetary and substellar companions at small angular separations is a rapidly advancing field. Dedicated high-contrast imaging instruments... Show moreContext. The direct detection and characterization of planetary and substellar companions at small angular separations is a rapidly advancing field. Dedicated high-contrast imaging instruments deliver unprecedented sensitivity, enabling detailed insights into the atmospheres of young low-mass companions. In addition, improvements in data reduction and point spread function (PSF)-subtraction algorithms are equally relevant for maximizing the scientific yield, both from new and archival data sets.Aims. We aim at developing a generic and modular data-reduction pipeline for processing and analysis of high-contrast imaging data obtained with pupil-stabilized observations. The package should be scalable and robust for future implementations and particularly suitable for the 3–5 m wavelength range where typically thousands of frames have to be processed and an accurate subtraction of the thermal background emission is critical.Methods. PynPoint is written in Python 2.7 and applies various image-processing techniques, as well as statistical tools for analyzing the data, building on open-source Python packages. The current version of PynPoint has evolved from an earlier version that was developed as a PSF-subtraction tool based on principal component analysis (PCA).Results. The architecture of PynPoint has been redesigned with the core functionalities decoupled from the pipeline modules. Modules have been implemented for dedicated processing and analysis steps, including background subtraction, frame registration, PSF subtraction, photometric and astrometric measurements, and estimation of detection limits. The pipeline package enables end-to-end data reduction of pupil-stabilized data and supports classical dithering and coronagraphic data sets. As an example, we processed archival VLT/NACO L0 and M0 data of Pic b and reassessed the brightness and position of the planet with a Markov chain Monte Carlo analysis; we also provide a derivation of the photometric error budget. Show less
We present the first measurements of the Lyman-continuum photon production efficiency xi(ion.0) at z similar to 4-5 for galaxies fainter than 0.2 L* (-19 mag). xi(ion.0) quantifies the production... Show moreWe present the first measurements of the Lyman-continuum photon production efficiency xi(ion.0) at z similar to 4-5 for galaxies fainter than 0.2 L* (-19 mag). xi(ion.0) quantifies the production rate of ionizing photons with respect to the UV luminosity density assuming a fiducial escape fraction of zero. Extending previous measurements of xi(ion.0) to the faint population is important, as ultra-faint galaxies are expected to contribute the bulk of the ionizing emissivity. We probe xi(ion.0) to such faint magnitudes by taking advantage of 200-h depth Spitzer/IRAC observations from the GREATS program and approximate to 300 3 < z < 6 galaxies with spectroscopic redshifts from the MUSE GTO Deep + Wide programs. Stacked IRAC [3.6] [4.5] colors are derived and used to infer the H alpha rest-frame equivalent widths, which range from 403 angstrom to 2818 angstrom. The derived xi(ion.0) is log(10)(xi(ion.0)/Hz erg(-1)) = 25.36 0.08 over-20.5 < Muv <-17.5, similar to those derived for brighter galaxy samples at the same redshift and therefore suggesting that 6011 shows no strong dependence on M-UV. The xi(ion.0) values found in our sample imply that the Lyman-continuum escape fraction for M-UV approximate to-19 star-forming galaxies cannot exceed approximate to 8-20% in the reionization era. Show less
