The bimodal [Mg/Fe] versus [Fe/H] bulge sequence as revealed by APOGEE DR14

Context. The Galactic bulge has a bimodal metallicity distribution function: different kinematic, spatial, and, potentially, age distributions characterize the metal-poor and metal-rich components. Despite this observed dichotomy, which argues for different formation channels for those stars, the distribution of bulge stars in the α-abundance versus metallicity plane has been found so far to be a rather smooth single sequence. Aims. We use data from the fourteenth data release of the APOGEE spectroscopic survey (DR14) to investigate the distribution in the Mg abundance (as tracer of the α-elements)-versus-metallicity plane of a sample of stars selected to be in the inner region of the bulge. Methods. A clean sample has been selected from the DR14 using a set of data- and pipeline-flags to ensure the quality of their fundamental parameters and elemental abundances. An additional selection made use of computed spectro-photometric distances to select a sample of likely bulge stars as those with RGC ≤ 3.5 kpc. We adopt magnesium abundance as an α-abundance proxy for our clean sample as it has been proven to be the most accurate α-element as determined by ASPCAP, the pipeline for data products from APOGEE spectra. Results. From the distribution of our bulge sample in the [Mg/Fe]-versus-[Fe/H] plane, we found that the sequence is bimodal. This bimodality is given by the presence of a low-Mg sequence of stars parallel to the main high-Mg sequence over a range of ∼0.5 dex around solar metallicity. The two sequences merge above [Fe/H] ∼ 0.15 dex into a single sequence whose dispersion in [Mg/Fe] is larger than either of the two sequences visible at lower metallicity. This result is confirmed when we consider stars in our sample that are inside the bulge region according to trustworthy Gaia DR2 distances.

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Proteomic Advances in Milk and Dairy Products

Molecules ◽

10.3390/molecules26133832 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3832

Author(s):

Rubén Agregán ◽

Noemí Echegaray ◽

María López-Pedrouso ◽

Radwan Kharabsheh ◽

Daniel Franco ◽

...

Keyword(s):

Dairy Products ◽

Two Dimensional Gel Electrophoresis ◽

Vast Number ◽

Post Translational Modifications ◽

Fundamental Parameters ◽

Complex Fluid ◽

Proteins And Peptides ◽

Milk And Dairy Products

Proteomics is a new area of study that in recent decades has provided great advances in the field of medicine. However, its enormous potential for the study of proteomes makes it also applicable to other areas of science. Milk is a highly heterogeneous and complex fluid, where there are numerous genetic variants and isoforms with post-translational modifications (PTMs). Due to the vast number of proteins and peptides existing in its matrix, proteomics is presented as a powerful tool for the characterization of milk samples and their products. The technology developed to date for the separation and characterization of the milk proteome, such as two-dimensional gel electrophoresis (2DE) technology and especially mass spectrometry (MS) have allowed an exhaustive characterization of the proteins and peptides present in milk and dairy products with enormous applications in the industry for the control of fundamental parameters, such as microbiological safety, the guarantee of authenticity, or the control of the transformations carried out, aimed to increase the quality of the final product.

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Flares in open clusters with K2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834400 ◽

2019 ◽

Vol 622 ◽

pp. A133 ◽

Cited By ~ 20

Author(s):

Ekaterina Ilin ◽

Sarah J. Schmidt ◽

James R. A. Davenport ◽

Klaus G. Strassmeier

Keyword(s):

Open Clusters ◽

Generation Process ◽

M Dwarfs ◽

Frequency Distributions ◽

Fundamental Parameters ◽

Physical Conditions ◽

Broad Energy Range ◽

Solar Metallicity ◽

Age Relation ◽

The Time Domain

Context. The presence and strength of a stellar magnetic field and activity is rooted in a star’s fundamental parameters such as mass and age. Can flares serve as an accurate stellar “clock”? Aims. To explore if we can quantify an activity-age relation in the form of a flaring-age relation, we measured trends in the flaring rates and energies for stars with different masses and ages. Methods. We investigated the time-domain photometry provided by Kepler’s follow-up mission K2 and searched for flares in three solar metallicity open clusters with well-known ages, M 45 (0.125 Gyr), M 44 (0.63 Gyr), and M 67 (4.3 Gyr). We updated and employed the automated flare finding and analysis pipeline Appaloosa, originally designed for Kepler. We introduced a synthetic flare injection and recovery sub-routine to ascribe detection and energy recovery rates for flares in a broad energy range for each light curve. Results. We collect a sample of 1761 stars, mostly late-K to mid-M dwarfs and found 751 flare candidates with energies ranging from 4 × 1032 erg to 6 × 1034 erg, of which 596 belong to M 45, 155 to M 44, and none to M 67. We find that flaring activity depends both on Teff, and age. But all flare frequency distributions have similar slopes with α ≈ 2.0−2.4, supporting a universal flare generation process. We discuss implications for the physical conditions under which flares occur, and how the sample’s metallicity and multiplicity affect our results.

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GALACTICNUCLEUS: A high angular resolution JHKs imaging survey of the Galactic centre

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732002 ◽

2018 ◽

Vol 610 ◽

pp. A83 ◽

Cited By ~ 22

Author(s):

F. Nogueras-Lara ◽

A. T. Gallego-Calvente ◽

H. Dong ◽

E. Gallego-Cano ◽

J. H. V. Girard ◽

...

Keyword(s):

Near Infrared ◽

Angular Resolution ◽

Infrared Camera ◽

Stellar Model ◽

Galactic Centre ◽

High Angular Resolution ◽

Wide Field ◽

Photometric Calibration ◽

Solar Metallicity

Context. The Galactic centre (GC) is of fundamental astrophysical interest, but existing near-infrared surveys fall short covering it adequately, either in terms of angular resolution, multi-wavelength coverage, or both. Here we introduce the GALACTICNUCLEUS survey, a JHKs imaging survey of the centre of the Milky Way with a 0.2″ angular resolution. Aims. The purpose of this paper is to present the observations of Field 1 of our survey, centred approximately on SgrA* with an approximate size of 7.95′ × 3.43′. We describe the observational set-up and data reduction pipeline and discuss the quality of the data. Finally, we present the analysis of the data. Methods. The data were acquired with the near-infrared camera High Acuity Wide field K-band Imager (HAWK-I) at the ESO Very Large Telescope (VLT). Short readout times in combination with the speckle holography algorithm allowed us to produce final images with a stable, Gaussian PSF (point spread function) of 0.2″ FWHM (full width at half maximum). Astrometric calibration is achieved via the VISTA Variables in the Via Lactea (VVV) survey and photometric calibration is based on the SIRIUS/Infrared Survey Facility telescope (IRSF) survey. The quality of the data is assessed by comparison between observations of the same field with different detectors of HAWK-I and at different times. Results. We reach 5σ detection limits of approximately J = 22, H = 21, and Ks = 20. The photometric uncertainties are less than 0.05 at J ≲ 20, H ≲ 17, and Ks ≲ 16. We can distinguish five stellar populations in the colour-magnitude diagrams; three of them appear to belong to foreground spiral arms, and the other two correspond to high- and low-extinction star groups at the GC. We use our data to analyse the near-infrared extinction curve and find some evidence for a possible difference between the extinction index between J − H and H − Ks. However, we conclude that it can be described very well by a power law with an index of αJHKs = 2.30 ± 0.08. We do not find any evidence that this index depends on the position along the line of sight, or on the absolute value of the extinction. We produce extinction maps that show the clumpiness of the ISM (interstellar medium) at the GC. Finally, we estimate that the majority of the stars have solar or super-solar metallicity by comparing our extinction-corrected colour-magnitude diagrams with isochrones with different metallicities and a synthetic stellar model with a constant star formation.

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Local Stellar Kinematics from RAVE Data: IV. Solar Neighbourhood Age–Metallicity Relation

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2013.21 ◽

2013 ◽

Vol 30 ◽

Cited By ~ 8

Author(s):

Ş. Duran ◽

S. Ak ◽

S. Bilir ◽

S. Karaali ◽

T. Ak ◽

...

Keyword(s):

Radial Velocity ◽

Spectral Type ◽

Stellar Kinematics ◽

Bayesian Procedure ◽

Experiment Data ◽

Data Release ◽

Galactic Population ◽

Effective Temperatures ◽

Metallicity Distribution ◽

Total Velocity

AbstractWe investigated the age–metallicity relation using a sample of 5691 F- and G-type dwarfs from RAdial Velocity Experiment Data Release 3 (RAVE DR3) by applying several constraints. (i) We selected stars with surface gravities log g(cm s−2) ≥ 3.8 and effective temperatures in the $5310\le T_{\text{eff}}\text{(K)}\le 7300$ range and obtained a dwarf sample. (ii) We plotted the dwarfs in metallicity sub-samples in the $T_{\text{eff}}\text{--}(J-K_s)_0$ plane to compare with the corresponding data of González Hernández & Bonifacio (2009) and identified the ones in agreement. (iii) We fitted the reduced dwarf sample obtained from constraints (i) and (ii) to the Padova isochrones and re-identified those which occupy the plane defined by isochrones with ages t ≤ 13 Gyr. (iv) Finally, we omitted dwarfs with total velocity errors larger than 10.63 km s−1. We estimated the ages using the Bayesian procedure of Jørgensen & Lindegren (2005). The largest age–metallicity slope was found for early F-type dwarfs. We found steeper slopes when we plotted the data as a function of spectral type rather than Galactic population. We noticed a substantial scatter in metallicity distribution at all ages. The metal-rich old dwarfs turned out to be G-type stars which can be interpreted as they migrated from the inner disc or bulge.

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Deep Chandra observations of the core of the Perseus cluster

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318005756 ◽

2018 ◽

Vol 14 (S342) ◽

pp. 127-132

Author(s):

Jeremy S. Sanders

Keyword(s):

Spatial Scales ◽

High Quality ◽

X Ray ◽

The Core ◽

Spatially Resolved ◽

Spatially Resolved Spectroscopy ◽

Perseus Cluster ◽

Metallicity Distribution

AbstractThe Perseus cluster is the X-ray brightest cluster in the sky and with deep Chandra observations we are able to map its central structure on very short spatial scales. In addition, the high quality of X-ray data allows detailed spatially-resolved spectroscopy. In this paper I review what these deep observations have told us about AGN feedback in clusters, sloshing and instabilities, and the metallicity distribution.

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Solving the distance discrepancy for the open cluster NGC 2453

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935243 ◽

2019 ◽

Vol 626 ◽

pp. A10 ◽

Cited By ~ 2

Author(s):

D. González-Díaz ◽

C. Moni Bidin ◽

E. Silva-Villa ◽

G. Carraro ◽

D. Majaess ◽

...

Keyword(s):

Planetary Nebula ◽

Open Cluster ◽

Independent Method ◽

Radial Velocities ◽

Line Of Sight ◽

Fundamental Parameters ◽

Data Release ◽

Cluster Distance ◽

Ubvri Photometry ◽

Good Agreement

Context. The open cluster (OC) NGC 2453 is of particular importance since it has been considered to host the planetary nebula (PN) NGC 2452, however their distances and radial velocities are strongly contested. Aims. In order to obtain a complete picture of the fundamental parameters of the OC NGC 2453, 11 potential members were studied. The results allowed us to resolve the PN NGC 2452 membership debate. Methods. Radial velocities for the 11 stars in NGC 2453 and the PN were measured and matched with Gaia data release 2 (DR2) to estimate the cluster distance. In addition, we used deep multi-band UBVRI photometry to get fundamental parameters of the cluster via isochrone fitting on the most likely cluster members, reducing inaccuracies due to field stars. Results. The distance of the OC NGC 2453 (4.7 ± 0.2 kpc) was obtained with an independent method solving the discrepancy reported in the literature. This result is in good agreement with an isochrone fitting of 40–50 Myr. On the other hand, the radial velocity of NGC 2453 (78 ± 3 km s−1) disagrees with the velocity of NGC 2452 (62 ± 2 km s−1). Our results show that the PN is a foreground object in the line of sight. Conclusions. Due to the discrepancies found in the parameters studied, we conclude that the PN NGC 2452 is not a member of the OC NGC 2453.

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Gaia Data Release 2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732516 ◽

2018 ◽

Vol 616 ◽

pp. A8 ◽

Cited By ~ 212

Author(s):

René Andrae ◽

Morgan Fouesneau ◽

Orlagh Creevey ◽

Christophe Ordenovic ◽

Nicolas Mary ◽

...

Keyword(s):

Training Data ◽

Line Of Sight ◽

The Third ◽

Data Release ◽

Individual Star ◽

Effective Temperatures ◽

Red Clump ◽

The Individual ◽

Bolometric Correction ◽

Clean Sample

The second Gaia data release (Gaia DR2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources. One band is the G band, the other two were obtained by integrating the Gaia prism spectra (BP and RP). We have used these three broad photometric bands to infer stellar effective temperatures, Teff, for all sources brighter than G = 17 mag with Teff in the range 3000–10 000 K (some 161 million sources). Using in addition the parallaxes, we infer the line-of-sight extinction, AG, and the reddening, E(BP − RP), for 88 million sources. Together with a bolometric correction we derive luminosity and radius for 77 million sources. These quantities as well as their estimated uncertainties are part of Gaia DR2. Here we describe the procedures by which these quantities were obtained, including the underlying assumptions, comparison with literature estimates, and the limitations of our results. Typical accuracies are of order 324 K (Teff), 0.46 mag (AG), 0.23 mag (E(BP − RP)), 15% (luminosity), and 10% (radius). Being based on only a small number of observable quantities and limited training data, our results are necessarily subject to some extreme assumptions that can lead to strong systematics in some cases (not included in the aforementioned accuracy estimates). One aspect is the non-negativity contraint of our estimates, in particular extinction, which we discuss. Yet in several regions of parameter space our results show very good performance, for example for red clump stars and solar analogues. Large uncertainties render the extinctions less useful at the individual star level, but they show good performance for ensemble estimates. We identify regimes in which our parameters should and should not be used and we define a “clean” sample. Despite the limitations, this is the largest catalogue of uniformly-inferred stellar parameters to date. More precise and detailed astrophysical parameters based on the full BP/RP spectrophotometry are planned as part of the third Gaia data release.

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Systematics and accuracy of VLBI astrometry: A comparison with Gaia Data Release 2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936996 ◽

2020 ◽

Vol 634 ◽

pp. A28

Author(s):

N. Liu ◽

S. B. Lambert ◽

Z. Zhu ◽

J.-C. Liu

Keyword(s):

Radio Source ◽

Positional Error ◽

Third Generation ◽

Noise Floor ◽

Vector Spherical Harmonics ◽

The Third ◽

Data Release ◽

Improved Accuracy ◽

External Check

Context. The third generation of the ICRF – ICRF3 – was published in 2018. This new fundamental catalog provides radio source positions measured independently at three bands: S/X, K, and X/Ka, representing three independent radio celestial frames which altogether constitute a multi-frequency ICRF. Aims. We aim to investigate the overall properties of the ICRF3 with the help of the Gaia Data Release 2 (Gaia DR2). This could serve as an external check of the quality of the ICRF3. Methods. The radio source positions of the ICRF3 catalog were compared with the Gaia DR2 positions of their optical counterparts at G < 18.7. Their properties were analyzed in terms of the dependency of the quoted error on the number of observations, on the declination, and the global difference, the latter revealed by means of expansions in the vector spherical harmonics. Results. The ICRF3 S/X-band catalog shows a more smooth dependency on the number of observations than the ICRF1 and ICRF2, while the K and X/Ka-band yield a dependency discrepancy at the number of observations of ∼50. The rotation of all ICRF catalogs show consistent results, except for the X-component of the X/Ka-band which arises from the positional error in the non-defining sources. No significant glides were found between the ICRF3 S/X-band component and Gaia DR2. However, the K- and X/Ka-band frames show a dipolar deformation in Y-component of +50 μas and several quadrupolar terms of 50 μas in an absolute sense. A significant glide along Z-axis exceeding 200 μas in the X/Ka-band was also reported. These systematics in the ICRF catalog are shown to be less dependent on the limiting magnitude of the Gaia sample when the number of common sources is sufficient (>100). Conclusions. The ICRF3 S/X-band catalog shows improved accuracy and systematics at the level of noise floor. But the zonal errors in the X/Ka-band should be noted, especially in the context of comparisons of multi-frequency positions for individual sources.

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The SkyMapper DR1.1 search for extremely metal-poor stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2550 ◽

2019 ◽

Vol 489 (4) ◽

pp. 5900-5918 ◽

Cited By ~ 9

Author(s):

G S Da Costa ◽

M S Bessell ◽

A D Mackey ◽

T Nordlander ◽

M Asplund ◽

...

Keyword(s):

Selection Process ◽

Normal Population ◽

Low Resolution ◽

Selection Procedures ◽

V Band ◽

Data Release ◽

Current Selection ◽

Metallicity Distribution ◽

Temperature Surface

ABSTRACT We present and discuss the results of a search for extremely metal-poor stars based on photometry from data release DR1.1 of the SkyMapper imaging survey of the southern sky. In particular, we outline our photometric selection procedures and describe the low-resolution (R ≈ 3000) spectroscopic follow-up observations that are used to provide estimates of effective temperature, surface gravity, and metallicity ([Fe/H]) for the candidates. The selection process is very efficient: of the 2618 candidates with low-resolution spectra that have photometric metallicity estimates less than or equal to −2.0, 41 per cent have [Fe/H] ≤ −2.75 and only approximately seven per cent have [Fe/H] > −2.0 dex. The most metal-poor candidate in the sample has [Fe/H] < −4.75 and is notably carbon rich. Except at the lowest metallicities ([Fe/H] < −4), the stars observed spectroscopically are dominated by a ‘carbon-normal’ population with [C/Fe]1D, LTE ≤ +1 dex. Consideration of the A(C)1D, LTE versus [Fe/H]1D, LTE diagram suggests that the current selection process is strongly biased against stars with A(C)1D, LTE > 7.3 (predominantly CEMP-s) while any bias against stars with A(C)1D, LTE < 7.3 and [C/Fe]1D,LTE > +1 (predominantly CEMP-no) is not readily quantifiable given the uncertainty in the SkyMapper v-band DR1.1 photometry. We find that the metallicity distribution function of the observed sample has a power-law slope of Δ(Log N)/Δ[Fe/H] = 1.5 ± 0.1 dex per dex for −4.0 ≤ [Fe/H] ≤ −2.75, but appears to drop abruptly at [Fe/H] ≈ −4.2, in line with previous studies.

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Gaia Data Release 2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832756 ◽

2018 ◽

Vol 616 ◽

pp. A4 ◽

Cited By ~ 291

Author(s):

D. W. Evans ◽

M. Riello ◽

F. De Angeli ◽

J. M. Carrasco ◽

P. Montegriffo ◽

...

Keyword(s):

Quality Assessment ◽

Data Release ◽

Systematic Effects ◽

Best Estimates

Aims. We describe the photometric content of the second data release of the Gaia project (Gaia DR2) and its validation along with the quality of the data. Methods. The validation was mainly carried out using an internal analysis of the photometry. External comparisons were also made, but were limited by the precision and systematics that may be present in the external catalogues used. Results. In addition to the photometric quality assessment, we present the best estimates of the three photometric passbands. Various colour-colour transformations are also derived to enable the users to convert between the Gaia and commonly used passbands. Conclusions. The internal analysis of the data shows that the photometric calibrations can reach a precision as low as 2 mmag on individual CCD measurements. Other tests show that systematic effects are present in the data at the 10 mmag level.

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