26Al yields from rotating Wolf--Rayet star models

We present new $^{26}$Al stellar yields from rotating Wolf--Rayet stellar models which, at solar metallicity, well reproduce the observed properties of the Wolf-Rayet populations. These new yields are enhanced with respect to non--rotating models, even with respect to non--rotating models computed with enhanced mass loss rates. We briefly discuss some implications of the use of these new yields for estimating the global contribution of Wolf-Rayet stars to the quantity of $^{26}$Al now present in the Milky Way.Comment: 6 pages, 2 figures, to appear in New Astronomy Review

Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters

We have recently reported the discovery of five low redshift Lyman continuum (LyC) emitters (LCEs, hereafter) with absolute escape fractions fesc(LyC) ranging from 6 to 13%, higher than previously found, and which more than doubles the number of low redshift LCEs.We use these observations to test theoretical predictions about a link between the characteristics of the Lyman-alpha (Lya) line from galaxies and the escape of ionising photons. We analyse the Lya spectra of eight LCEs of the local Universe observed with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (our five leakers and three galaxies from the litterature), and compare their strengths and shapes to the theoretical criteria and comparison samples of local galaxies: the Lyman Alpha Reference Survey, Lyman Break Analogs, Green Peas, and the high-redshift strong LyC leaker Ion2. Our LCEs are found to be strong Lya emitters, with high equivalent widths, EW(Lya)> 70 {\AA}, and large Lya escape fractions, fesc(Lya) > 20%. The Lya profiles are all double-peaked with a small peak separation, in agreement with our theoretical expectations. They also have no underlying absorption at the Lya position. All these characteristics are very different from the Lya properties of typical star-forming galaxies of the local Universe. A subset of the comparison samples (2-3 Green Pea galaxies) share these extreme values, indicating that they could also be leaking. We also find a strong correlation between the star formation rate surface density and the escape fraction of ionising photons, indicating that the compactness of star-forming regions plays a role in shaping low column density paths in the interstellar medium of LCEs. The Lya properties of LCEs are peculiar: Lya can be used as a reliable tracer of LyC escape from galaxies, in complement to other indirect diagnostics proposed in the literature.Comment: 11 pages, 10 figures, accepted for publication in A&

Grids of stellar models. VIII. From 0.4 to 1.0 Msun at Z=0.020 and Z=0.001, with the MHD equation of state

We present stellar evolutionary models covering the mass range from 0.4 to 1 Msun calculated for metallicities Z=0.020 and 0.001 with the MHD equation of state (Hummer & Mihalas, 1988; Mihalas et al. 1988; D\"appen et al. 1988). A parallel calculation using the OPAL (Rogers et al. 1996) equation of state has been made to demonstrate the adequacy of the MHD equation of state in the range of 1.0 to 0.8 Msun (the lower end of the OPAL tables). Below, down to 0.4 Msun, we have justified the use of the MHD equation of state by theoretical arguments and the findings of Chabrier & Baraffe (1997). We use the radiative opacities by Iglesias & Rogers (1996), completed with the atomic and molecular opacities by Alexander & Fergusson (1994). We follow the evolution from the Hayashi fully convective configuration up to the red giant tip for the most massive stars, and up to an age of 20 Gyr for the less massive ones. We compare our solar-metallicity models with recent models computed by other groups and with observations. The present stellar models complete the set of grids computed with the same up-to-date input physics by the Geneva group [Z=0.020 and 0.001, Schaller et al. (1992), Bernasconi (1996), and Charbonnel et al. (1996); Z=0.008, Schaerer et al. (1992); Z=0.004, Charbonnel et al. (1993); Z=0.040, Schaerer et al. (1993); Z=0.10, Mowlavi et al. (1998); enhanced mass loss rate evolutionary tracks, Meynet et al. (1994)].Comment: Accepted for publication in A&A Supplement Serie

The Stanley Foundation Bipolar Network: Results of the naturalistic follow-up study after 2.5 years of follow-up in the German centres

The Stanley Foundation Bipolar Network (SFBN) is an international, multisite network investigating the characteristics and course of bipolar disorder. Methods (history, ratings and longitudinal follow-up) are standardized and equally applied in all 7 centres. This article describes demographics and illness characteristics of the first 152 German patients enrolled in them SFBN as well as the results of 2.5 years of follow-up. Patients in Germany were usually enrolled after hospitalisation. More than 72% of the study population suffered from bipolar I disorder and 25% from bipolar 11 disorder. The mean +/- SD age of the study participants was 42.08 +/- 13.5 years, and the mean SD age of onset 24.44 +/- 10.9 years. More than 40% of the sample reported a rapid-cycling course in history, and even more a cycle acceleration overtime. 37% attempted suicide at least once. 36% had an additional Axis I disorder, with alcohol abuse being the most common one, followed by anxiety disorders. During the follow-up period, only 27% remained stable, 56% had a recurrence, 12.8% perceived subsyndromal symptoms despite treatment and regular visits. 27% suffered from a rapid-cycling course during the follow-up period. Recurrences were significantly associated with bipolar I disorder, an additional comorbid Axis I disorder, rapid cycling in history, a higher number of mood stabilizers and the long-term use of typical antipsychotics. Rapid cycling during follow-up was only associated with a rapidcycling course in history, a higher number of mood stabilizers and at least one suicide attempt in history. Copyright (c) 2003 S. Karger AG, Basel

Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies

Following our first detection reported in Izotov et al. (2016), we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST). These galaxies, at redshifts of z~0.3, are characterized by high emission-line flux ratios [OIII]5007/[OII]3727 > 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ~6%-13%, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Lyalpha emission lines are detected in the spectra of all four galaxies, compatible with predictions for Lyman continuum leakers. We find escape fractions of Lyalpha, fesc(Lyalpha) ~20%-40%, among the highest known for Lyalpha emitters (LAEs). Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the center and exponential discs in the outskirts with disc scale lengths alpha in the range ~0.6-1.4 kpc. Our galaxies are characterized by low metallicity, ~1/8-1/5 solar, low stellar mass ~(0.2 - 4)e9 Msun, high star formation rates SFR~14-36 Msun/yr, and high SFR densities Sigma~2-35 Msun/yr/kpc^2. These properties are comparable to those of high-redshift star-forming galaxies. Finally, our observations, combined with our first detection reported in Izotov et al. (2016), reveal that a selection for compact star-forming galaxies showing high [OIII]5007/[OII]3727 ratios appears to pick up very efficiently sources with escaping Lyman continuum radiation: all five of our selected galaxies are LyC leakers.Comment: 21 pages, 14 figures, accepted for publication in MNRAS; corrected Lyalpha escape fraction

Do galaxies that leak ionizing photons have extreme outflows?

To reionize the early universe, high-energy photons must escape the galaxies that produce them. It has been suggested that stellar feedback drives galactic outflows out of star-forming regions, creating low density channels through which ionizing photons escape into the inter-galactic medium. We compare the galactic outflow properties of confirmed Lyman continuum (LyC) leaking galaxies to a control sample of nearby star-forming galaxies to explore whether the outflows from leakers are extreme as compared to the control sample. We use data from the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the equivalent widths and velocities of Si II and Si III absorption lines, tracing neutral and ionized galactic outflows. We find that the Si II and Si III equivalent widths of the LyC leakers reside on the low-end of the trend established by the control sample. The leakers' velocities are not statistically different than the control sample, but their absorption line profiles have a different asymmetry: their central velocities are closer to their maximum velocities. The outflow kinematics and equivalent widths are consistent with the scaling relations between outflow properties and host galaxy properties -- most notably metallicity -- defined by the control sample. Additionally, we use the Ly\alpha\ profiles to show that the Si II equivalent width scales with the Ly\alpha\ peak velocity separation. We determine that the low equivalent widths of the leakers are likely driven by low metallicities and low H I column densities, consistent with a density-bounded ionization region, although we cannot rule out significant variations in covering fraction. While we do not find that the LyC leakers have extreme outflow velocities, the low maximum-to-central velocity ratios demonstrate the importance of the acceleration and density profiles for LyC and Ly\alpha\ escape. [abridged]Comment: 17 pages, 8 Figures. Accepted for publication in Astronomy & Astrophysic

J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons

We report the detection of the Lyman continuum (LyC) radiation of the compact star-forming galaxy (SFG) J1154+2443 observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. This galaxy, at a redshift of z=0.3690, is characterized by a high emission-line flux ratio O32=[OIII]5007/[OII]3727=11.5. The escape fraction of the LyC radiation fesc(LyC) in this galaxy is 46 per cent, the highest value found so far in low-redshift SFGs and one of the highest values found in galaxies at any redshift. The narrow double-peaked Lya emission line is detected in the spectrum of J1154+2443 with a separation between the peaks Vsep of 199 km/s, one of the lowest known for Lya-emitting galaxies, implying a high fesc(Lya). Comparing the extinction-corrected Lya/Hb flux ratio with the case B value we find fesc(Lya) = 98 per cent. Our observations, combined with previous detections in the literature, reveal an increase of O32 with increasing fesc(LyC). We also find a tight anticorrelation between fesc(LyC) and Vsep. The surface brightness profile derived from the COS acquisition image reveals a bright star-forming region in the centre and an exponential disc in the outskirts with a disc scale length alpha=1.09 kpc. J1154+2443, compared to other known low-redshift LyC leakers, is characterized by the lowest metallicity, 12+logO/H=7.65+/-0.01, the lowest stellar mass M*=10^8.20 Msun, a similar star formation rate SFR=18.9 Msun/yr and a high specific SFR of 1.2x10^-7 yr^-1.Comment: 16 pages, 8 figures, accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1605.0516

A Preliminary Seismic Analysis of 51 Peg: Large and Small Spacings from Standard Models

We present a preliminary theoretical seismic study of the astronomically famous star 51 Peg. This is done by first performing a detailed analysis within the Hertzsprung-Russell diagram (HRD). Using the Yale stellar evolution code (YREC), a grid of stellar evolutionary tracks has been constructed for the masses 1.00 M_sun, 1.05 M_sun and 1.10 M_sun, in the metallicity range Z=0.024-0.044, and for values of the Galactic helium enrichment ratio DY/DZ in the range 0-2.5. Along these evolutionary tracks, we select 75 stellar model candidates that fall within the 51 Peg observational error box in the HRD (all turn out to have masses of 1.05 M_sun and 1.10 M_sun. The corresponding allowable age range for these models, which depends sensitively on the parameters of the model, is relatively large and is ~2.5 - 5.5 Gyr. For each of the 75 models, a non-radial pulsation analysis is carried out, and the large and small frequency spacings are calculated. The results show that just measuring the large and small frequency spacings will greatly reduce the present uncertainties in the derived physical parameters and in the age of 51 Peg. Finally we discuss briefly refinements in the physics of the models and in the method of analysis which will have to be included in future models to make the best of the precise frequency determinations expected from space observations.Comment: 22 pages, 5 figures, 3 tables. Accepted for publicaton by Ap

Starburst99: Synthesis Models for Galaxies with Active Star Formation

Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman (1995). We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid compiled by Lejeune et al. (1997). Several predictions which were not included in the previous publication are shown here for the first time. The models are presented in a homogeneous way for five metallicities between Z = 0.040 and 0.001 and three choices of the initial mass function. The age coverage is 10^6 to 10^9 yr. We also show the spectral energy distributions which are used to compute colors and other quantities. The full data set is available for retrieval at http://www.stsci.edu/science/starburst99/. This website allows users to run specific models with non-standard parameters as well. We also make the source code available to the community.Comment: 32 pages, LaTeX. All the Figures and the summary Table are located at http://www.stsci.edu/science/starburst99/, ApJ accepte