Cartography of Triangulum-Andromeda using SDSS stars

The outer Galactic halo is home to a number of substructures which still have an uncertain origin, but most likely are remnants of former interactions between the Galaxy and its former satellites. Triangulum-Andromeda (TriAnd) is one of these halo substructures, found as an overdensity of Two Micron All Sky Survey (2MASS) M giants. We analysed the region of TriAnd using photometric data from the Ninth Data Release of Sloan Digital Sky Survey. By comparing the observations with simulations from the TRILEGAL Galactic model, we were able to identify and map several scattered overdensities of main-sequence stars that seem to be associated with TriAnd over a large area covering ∼500 deg2. One of these excesses may represent a new stellar overdensity.We also briefly discuss an alternative hypothesis, according to which TriAnd is one of the troughs of oscillation rings in the Galactic disc

The first 62 AGN observed with SDSS-IV MaNGA – IV. Gas excitation and star formation rate distributions

We present maps of the ionized gas flux distributions, excitation, star formation rate (SFR), surface mass density ΣH+, and obtain total values of SFR and ionized gas masses M for 62 active galactic nuclei (AGN) observed with SDSS-IV MaNGA and compare them with those of a control sample of 112 non-active galaxies. The most luminous AGN – with L([OIII]λ5007)≥3.8×1040ergs−1, and those hosted by earlier type galaxies are dominated by Seyfert excitation within 0.2 effective radius Re from the nucleus, surrounded by LINER excitation or transition regions, while the less luminous and hosted by later-type galaxies show equally frequent LINER and Seyfert excitation within 0.2Re. The extent R of the region ionized by the AGN follows the relation R∝L([OIII])0.5 – as in the case of the broad-line region. The SFR distribution over the region ionized by hot stars is similar for AGN and controls, while the integrated SFR – in the range 10−3–10 M⊙ yr−1 is also similar for the late-type subsample, but higher in the AGN for 75 per cent of the early-type subsample. We thus conclude that there is no signature of AGN quenching star formation in the body of the galaxy in our sample. We also find that 66 per cent of the AGN have higher ionized gas masses M than the controls – in the range 105–3 × 107 M⊙ – while 75 per cent of the AGN have higher ΣH+ within 0.2Re than the control galaxie

Precessing winds from the nucleus of the prototype Red Geyser?

Supermassive black holes (SMBHs) are present at the centre of most galaxies, with the related mass accretion processes giving origin to outflows in active galactic nuclei (AGNs). It has been presumed that only intense winds from luminous AGNs were able to suppress star formation until the discovery of a new class of galaxies with no recent star formation and with the nucleus in a quiescent state showing kpc scale outflows. We used SDSS MaNGA and Gemini Integral Field Spectroscopy of the prototype Red Geyser Akira and found that the orientation of the outflow changes by about 50° from its nucleus to kpc scales. A possible interpretation is that the outflow is produced by a precessing accretion disc due to a misalignment between the orientation of the disc and the spin of the SMBH. The precession of the central source is also supported by a similar change in the orientation of the ionization pattern. Although similar behaviour has commonly being reported for collimated relativistic jets, the precession of an AGN wide wind is reported here for the first time, implying on a larger work surface of the wind, which in turn increases the star formation suppression efficiency of the outflow

Accurate Atmospheric Parameters at Moderate Resolution Using Spectral Indices: Preliminary Application to the MARVELS Survey

Studies of Galactic chemical and dynamical evolution in the solar neighborhood depend on the availability of precise atmospheric parameters (Teff, [Fe/H] and log g) for solar-type stars. Many large-scale spectroscopic surveys operate at low to moderate spectral resolution for efficiency in observing large samples, which makes the stellar characterization difficult due to the high degree of blending of spectral features. While most surveys use spectral synthesis, in this work we employ an alternative method based on spectral indices to determine the atmospheric parameters of a sample of nearby FGK dwarfs and subgiants observed by the MARVELS survey at moderate resolving power (R~12,000). We have developed three codes to automatically normalize the observed spectra, measure the equivalent widths of the indices and, through the comparison of those with values calculated with pre-determined calibrations, derive the atmospheric parameters of the stars. The calibrations were built using a sample of 309 stars with precise stellar parameters obtained from the analysis of high-resolution FEROS spectra. A validation test of the method was conducted with a sample of 30 MARVELS targets that also have reliable atmospheric parameters from high-resolution spectroscopic analysis. Our approach was able to recover the parameters within 80 K for Teff, 0.05 dex for [Fe/H] and 0.15 dex for log g, values that are lower or equal to the typical external uncertainties found between different high-resolution analyzes. An additional test was performed with a subsample of 138 stars from the ELODIE stellar library and the literature atmospheric parameters were recovered within 125 K for Teff, 0.10 dex for [Fe/H] and 0.29 dex for log g. These results show that the spectral indices are a competitive tool to characterize stars with the intermediate resolution spectra.Comment: Accepted for publication in AJ. Abstract edited to comply with arXiv standards regarding the number of character

The first 62 AGN observed with SDSS-IV MaNGA – III : stellar and gas kinematics

We investigate the effects of active galactic nuclei (AGN) on the gas kinematics of their host galaxies, using MaNGA data for a sample of 62 AGN hosts and 109 control galaxies (inactive galaxies). We compare orientation of the line of nodes (kinematic position angle – PA) measured from the gas and stellar velocity fields for the two samples. We found that AGN hosts and control galaxies display similar kinematic PA offsets between gas and stars. However, we note that AGN have larger fractional velocity dispersion σ differences between gas and stars [σfrac = (σgas − σstars)/σstars] when compared to their controls, as obtained from the velocity dispersion values of the central (nuclear) pixel (2. 5 diameter). The AGN have a median value of σfrac of AGN = 0.04, while the median value for the control galaxies is CTR =−0.23. 75 per cent of the AGN show σfrac > −0.13, while 75 per cent of the normal galaxies show σfrac < −0.04, thus we suggest that the parameter σfrac can be used as an indicator of AGN activity. We find a correlation between the [OIII]λ5007 luminosity and σfrac for our sample. Our main conclusion is that the AGN already observed with MaNGA are not powerful enough to produce important outflows at galactic scales, but at 1–2 kpc scales, AGN feedback signatures are always present on their host galaxies

The first 62 AGNs observed with SDSS-IV MaNGA : I. Their characterization and definition of a control sample

We report the characterization of the first 62 Mapping Nearby Galaxies at the Apache Point Observatory active galactic nuclei (AGNs) hosts and the definition of a control sample of non-active galaxies. This control sample was selected in order to match the AGN hosts in terms of stellar mass, redshift, visual morphology and inclination. The stellar masses are in the range 9.4 < log M/M < 11.5, and most objects have redshifts ≤0.08. The AGN sample is mostly comprised low-luminosity AGN, with only 17 ‘strong AGN’ with L([O III]λ5007 Å) ≥ 3.8 × 1040 erg s−1. The inner 1–3 kpc of the control sample galaxies are dominated by the oldest (≥ 4Gyr) component, with a small contribution of intermediate age and young stars (<940 Myr). Examining the relationship between the stellar population properties and L([O III]), we find that with increasing L([O III]), the AGN exhibit a decreasing contribution from the oldest stellar population relative to control galaxies and an increasing contribution from the younger components (∼40 Myr).We also find a correlation of the mean age differences (AGN–control) with L([O III]), in the sense that more luminous AGNs are younger than the control objects, while the low-luminosity AGNs are older. These results support a connection between the growth of the galaxy bulge via formation of new stars and the growth of the Supermassive Black Hole via accretion in the AGN phase

Exploring the brown dwarf desert : new substellar companions from the SDSS-III MARVELS survey

Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ∼5 au in the mass range of ∼10–80 MJup. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help assess the reality of the desert and provide insight to the formation and evolution of these objects. Here, we present 10 new brown dwarf and 2 low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III. These companions were selected from processed MARVELS data using the latest University of Florida Two Dimensional pipeline, which shows significant improvement and reduction of systematic errors over previous pipelines. The 10 brown dwarf companions range in mass from ∼13 to 76 MJup and have orbital radii of less than 1 au. The two stellar companions have minimum masses of ∼98 and 100 MJup. The host stars of the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03 ± 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence rate around solar-type stars with periods less than ∼300 d to be ∼0.56 per cent

A catalogue of structural and morphological measurements for DES Y1

We present a structural and morphological catalogue for 45 million objects selected from the first year data of the Dark Energy Survey (DES). Single Sersic fits and non-parametric ´ measurements are produced for g, r, and i filters. The parameters from the best-fitting Sersic ´ model (total magnitude, half-light radius, Sersic index, axis ratio, and position angle) are mea- ´ sured with GALFIT; the non-parametric coefficients (concentration, asymmetry, clumpiness, Gini, M20) are provided using the Zurich Estimator of Structural Types (ZEST+). To study the statistical uncertainties, we consider a sample of state-of-the-art image simulations with a realistic distribution in the input parameter space and then process and analyse them as we do with real data: this enables us to quantify the observational biases due to PSF blurring and magnitude effects and correct the measurements as a function of magnitude, galaxy size, Sersic ´ index (concentration for the analysis of the non-parametric measurements) and ellipticity. We present the largest structural catalogue to date: we find that accurate and complete measurements for all the structural parameters are typically obtained for galaxies with SEXTRACTOR MAG AUTO I ≤ 21. Indeed, the parameters in the filters i and r can be overall well recovered up to MAG AUTO ≤ 21.5, corresponding to a fitting completeness of ∼90 per cent below this threshold, for a total of 25 million galaxies. The combination of parametric and non-parametric structural measurements makes this catalogue an important instrument to explore and understand how galaxies form and evolve. The catalogue described in this paper will be publicly released alongside the DES collaboration Y1 cosmology data products at the following URL: https://des.ncsa.illinois.edu/releases

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected

Discovery of a z = 0.65 post-starburst BAL quasar in the DES supernova fields

We present the discovery of a z = 0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad Fe II (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario