arXiv subjects

M. Hempel

Publications and source records attributed to M. Hempel.

At least 19 recordsLinked to original sources

arXiv2025

The VVV near-IR galaxy catalogue of the southern Galactic disc

The distribution of galaxies in the Zone of Avoidance (ZoA) is incomplete due to the presence of our own Galaxy. Our research focused on the identification and characterisation of galaxies in the ZoA, using the new near-infrared data from the VVVX survey in the regions that cover the southern Galactic disc. We used our previously-established procedure based on photometric and morphological criteria to identify galaxies. The large data volume collected by the VVVX required alternatives to visual inspection, including artificial intelligence techniques, such as classifiers based on neural networks. The VVV NIR galaxy catalogue is presented, covering the southern Galactic disc, significantly extending the vision down to $K^0_s=16$ mag throughout the ZoA. This catalogue provides positions, photometric and morphological parameters for a total of 167,559 galaxies with their probabilities determined by the CNN and XGBoost algorithms based on image and photometric data, respectively. The construction of the catalogue involves the employment of optimal probability criteria. 14% of these galaxies were confirmed by visual inspection or by matching with previous catalogues. The peculiarities exhibited by distinct regions across the Galactic disc, along with the characteristics of the galaxies, are thoroughly examined. The catalogue serves as a valuable resource for extragalactic studies within the ZoA, providing a crucial complement to the forthcoming radio catalogues and future surveys utilizing the Vera C.~Rubin Observatory and the Nancy Grace Roman Space Telescope. We present a deep galaxy map, covering a 1080 sq. deg. region, which reveals that the apparent galaxy density is predominantly influenced by foreground extinction from the Milky Way. However, the presence of intrinsic inhomogeneities, potentially associated with candidate galaxy groups or clusters and filaments, is also discernible.

astro-ph.GA↗

arXiv2024

The VISTA Variables in the V\'ia L\'actea eXtended (VVVX) ESO public survey: Completion of the observations and legacy

The ESO public survey VISTA Variables in the V\'ia L\'actea (VVV) surveyed the inner Galactic bulge and the adjacent southern Galactic disk from $2009-2015$. Upon its conclusion, the complementary VVV eXtended (VVVX) survey has expanded both the temporal as well as spatial coverage of the original VVV area, widening it from $562$ to $1700$ sq. deg., as well as providing additional epochs in $JHK_{\rm s}$ filters from $2016-2023$. With the completion of VVVX observations during the first semester of 2023, we present here the observing strategy, a description of data quality and access, and the legacy of VVVX. VVVX took $\sim 2000$ hours, covering about 4% of the sky in the bulge and southern disk. VVVX covered most of the gaps left between the VVV and the VISTA Hemisphere Survey (VHS) areas and extended the VVV time baseline in the obscured regions affected by high extinction and hence hidden from optical observations. VVVX provides a deep $JHK_{\rm s}$ catalogue of $\gtrsim 1.5\times10^9$ point sources, as well as a $K_{\rm s}$ band catalogue of $\sim 10^7$ variable sources. Within the existing VVV area, we produced a $5D$ map of the surveyed region by combining positions, distances, and proper motions of well-understood distance indicators such as red clump stars, RR Lyrae, and Cepheid variables. In March 2023 we successfully finished the VVVX survey observations that started in 2016, an accomplishment for ESO Paranal Observatory upon 4200 hours of observations for VVV+VVVX. The VVV+VVVX catalogues complement those from the Gaia mission at low Galactic latitudes and provide spectroscopic targets for the forthcoming ESO high-multiplex spectrographs MOONS and 4MOST.

astro-ph.GA↗

arXiv2023

The VVV near-IR galaxy catalogue in a Northern part of the Galactic disc

The automated identification of extragalactic objects in large surveys provides reliable and reproducible samples of galaxies in less time than procedures involving human interaction. However, regions near the Galactic disc are more challenging due to the dust extinction. We present the methodology for the automatic classification of galaxies and non-galaxies at low Galactic latitude regions using both images and, photometric and morphological near-IR data from the VVVX survey. Using the VVV-NIRGC, we analyse by statistical methods the most relevant features for galaxy identification. This catalogue was used to train a CNN with image data and an XGBoost model with both photometric and morphological data and then to generate a dataset of extragalactic candidates. This allows us to derive probability catalogues used to analyse the completeness and purity as a function of the configuration parameters and to explore the best combinations of the models. As a test case, we apply this methodology to the Northern disc region of the VVVX survey, obtaining 172,396 extragalatic candidates with probabilities of being galaxies. We analyse the performance of our methodology in the VVV disc, reaching an F1-score of 0.67, a 65 per cent purity and a 69 per cent completeness. We present the VVV-NIR Galaxy Catalogue: Northern part of the Galactic disc comprising 1,003 new galaxies, with probabilities greater than 0.6 for either model, with visual inspection and with only 2 previously identified galaxies. In the future, we intend to apply this methodology to other areas of the VVVX survey.

astro-ph.GA↗

arXiv2022

The globular cluster system of the nearest Seyfert II galaxy Circinus

Context. The globular cluster (GC) system of Circinus galaxy has not been probed previously partly because of the location of the galaxy at - 3.8$^\circ$ Galactic latitude which suffers severely from interstellar extinction, stellar crowding, and Galactic foreground contamination. However, the deep near-infrared (NIR) photometry by the VISTA Variables in the Via Láctea Extended Survey (VVVX) in combination with the precise astrometry of Gaia EDR3 allow us to map GCs in this region. Aims. Our long-term goal is to study and characterise the distributions of GCs and Ultra-compact dwarfs of Circinus galaxy which is the nearest Seyfert II galaxy. Here we conduct the first pilot search for GCs in this galaxy. Methods. We use NIR VVVX photometry in combination with Gaia EDR3 astrometric features such as astrometric excess noise and BP/RP excess factor to build the first homogeneous catalogue of GCs in Circinus galaxy. A robust combination of selection criteria allows us to effectively clean interlopers from our sample. Results. We report the detection of$\sim$ 70 GC candidates in this galaxy at a 3 $σ$ confidence level. They show a bimodal colour distribution with the blue peak at (G-Ks)$_0$ = 0.985$\pm$0.127 mag with a dispersion of 0.211$\pm$0.091 mag and the red peak at (G-Ks)$_0$ = 1.625$\pm$0.177 mag with a dispersion of 0.482$\pm$0.114 mag. A GC specific frequency (S$_N$) of 1.3$\pm$0.2 was derived for the galaxy, and we estimated a total population of 120$\pm$40 GCs. Based on the projected radial distribution it appears that Circinus has a different distribution of GC candidates than MW and M31. Conclusions. We demonstrate that Circinus galaxy hosts a sizeable number of cluster candidates. This result is the first leap towards understanding the evolution of old stellar clusters in this galaxy.

astro-ph.GA↗

arXiv2022

RVSPY -- Radial Velocity Survey for Planets around Young Stars. Target characterization and high-cadence survey

We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), characterise our target stars, and search for substellar companions at orbital separations smaller than a few au from the host star. We use the FEROS spectrograph to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars most of which are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr, and a median distance of 45 pc. We determine for all target stars their basic stellar parameters and present the results of the high-cadence RV survey and activity characterization. We achieve a median single-measurement RV precision of 6 m/s and derive the short-term intrinsic RV scatter of our targets (median 22 m/s), which is mostly caused by stellar activity and decays with age from >100 m/s at <20 Myr to <20 m/s at >500 Myr. We discover six previously unknown close companions with orbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We detect no hot companion with an orbital period <10 days down to a median mass limit of ~1 M_Jup for stars younger than 500 Myr, which is still compatible with the established occurrence rate of such companions around main-sequence stars. We find significant RV periodicities between 1.3 and 4.5 days for 14 stars, which are, however, all caused by rotational modulation due to starspots. We also analyse the TESS photometric time series data and find significant periodicities for most of the stars. For 11 stars, the photometric periods are also clearly detected in the RV data. We also derive stellar rotation periods ranging from 1 to 10 days for 91 stars, mostly from TESS data. From the intrinsic activity-related short-term RV jitter, we derive the expected mass-detection thresholds for longer-period companions.

astro-ph.EP↗

arXiv2022

A new low-luminosity globular cluster discovered in the Milky Way with the VVVX survey

The VISTA Variables in the Via Láctea Extended Survey (VVVX) allows probing previously unexplored regions of the inner Milky Way (MW). We are looking for new candidate globular clusters (GCs), with the aim of completing the census of the MW GC system. We searched and characterised new GCs, using a combination of the near-IR VVVX survey and 2MASS datasets, and the optical Gaia EDR3 photometry and its precise proper motions (PMs). We report the discovery of a new Galactic GC, named Garro 02, situated at RA=18:05:51.1, Dec=-17:42:02 and l=12.042 deg, b=+1.656 deg. Performing a PM-decontamination procedure, we built a final catalogue with all cluster members, on which we performed a photometric analysis. We calculated a reddening of $E(J-K_s)=1.07\pm 0.06$ mag and extinction of $A_{Ks}=0.79\pm 0.04$ mag in the near-IR; while $E(BP-RP)=2.40\pm 0.01$ mag and $A_{G}=4.80\pm 0.02$ mag in optical passbands. Its heliocentric distance is $D=5.6\pm 0.8$ kpc, which places Garro 02 at a Galactocentric distance of $R_G=2.9$ kpc and Z=0.006 kpc above the Galactic plane. We estimated the metallicity and age by comparison with known GCs and by fitting PARSEC isochrones, finding [Fe/H]$=-1.30\pm 0.2$ dex and age=$12\pm 2$ Gyr. We derived the mean cluster PM of $(μ_α^{\ast}, μ_δ) = (-6.07\pm 0.62, -6.15\pm 0.75)$ mas yr$^{-1}$. We calculated the cluster luminosity in the near-IR of $M_{Ks}=-7.52\pm 1.23$ mag, which is equivalent to $M_{V}=-5.44$ mag. The core and tidal radii from the radial density profile are $r_c =1.25\pm 0.27$ arcmin (2.07 pc) and $r_t = 7.13\pm 3.83$ arcmin (11.82 pc), respectively. We confirm Garro 02 as a new genuine Galactic GC, located in the MW bulge. It is a low-luminosity, metal-poor, and old GC, and it is a lucky survivor of the strong dynamical processes that occurred during the MW's entire life.

astro-ph.GA↗

arXiv2021

Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates

The Galactic globular cluster system is incomplete, especially in the low latitude regions of the Galactic bulge and disk. We report the physical characterization of twelve star clusters in the Milky Way, most of which are explored here for the first time. Our aim is determining their main physical parameters, such as reddening and extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), distances, in order to unveil their physical nature. We study the clusters using optical and near-infrared (NIR) datasets. We use the Gaia Early Data Release 3 (EDR3) PMs in order to perform a PM-decontamination procedure and build final catalogues. We match the Gaia EDR3 with the VISTA Variables in the Vía Láctea extended (VVVX) survey and Two Micron All Sky survey (2MASS) in the NIR, in order to construct complete colour-magnitude diagrams (CMDs) and investigate the clusters properties. The extinctions are evaluated using existing reddening maps, spanning $0.09\lesssim A_{Ks}\lesssim 0.86$ mag and $0.89 \lesssim A_{G}\lesssim 4.72$ mag in the NIR and optical, respectively. We obtain their heliocentric distances, that range from about 4 to 20 kpc, placing these clusters at $3\lesssim R_{G}\lesssim 14$ kpc from the Galactic centre. The best PARSEC isochrone fit yields a metallicity range of $-1.8<$[Fe/H]$<+0.3$ and an approximative age range of $2<$Age$<14$ Gyr. We find that all clusters have low-luminosities, with $-6.9<M_{V}<-3.5$ mag. Based on our photometric analysis, we confirm the OC nature for Kronberger100, while we classify Patchick125 as a metal-poor GC, Ferrero54 as a metal-rich GC, and ESO92-18 as a possible old OC or young GC. The classification as GC candidates is also suggested for Kronberger99, Patchick122, Patchick126, Riddle15, FSR190 and Gaia2. We also conclude that Kronberger119 and Kronberger143 might be either old OCs or young GCs.

astro-ph.GA↗

arXiv2021

Discovery of new globular clusters in the Sagittarius dwarf galaxy

Context. Globular clusters (GCs) are witnesses of the past accretion events onto the Milky Way (MW). In particular, the GCs of the Sagittarius (Sgr) dwarf galaxy are important probes of an on-going merger. Aims. Our main goal is to search for new GC members of this dwarf galaxy using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared database combined with the Gaia Early Data Release 3 (EDR3) optical database. Methods. We investigated all VVVX-enabled discoveries of GC candidates in a region covering about 180 sq. deg. toward the bulge and the Sgr dwarf galaxy. We used multiband point-spread function photometry to obtain deep color-magnitude diagrams (CMDs) and luminosity functions (LFs) for all GC candidates, complemented by accurate Gaia-EDR3 proper motions (PMs) to select Sgr members and variability information to select RR Lyrae which are potential GC members. Results. After applying a strict PM cut to discard foreground bulge and disk stars, the CMDs and LFs for some of the GC candidates exhibit well defined red giant branches and red clump giant star peaks. We selected the best Sgr GCs, estimating their distances, reddenings, and associated RR Lyrae. Conclusions. We discover 12 new Sgr GC members, more than doubling the number of GCs known in this dwarf galaxy. In addition, there are 11 other GC candidates identified that are uncertain, awaiting better data for confirmation.

astro-ph.GA↗

arXiv2020

VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk

Milky Way globular clusters (MW GCs) are difficult to identify at low Galactic latitudes because of high differential extinction and heavy star crowding. The new deep near-IR images and photometry from the VISTA Variables in the Via Láctea Extended Survey (VVVX) allow us to chart previously unexplored regions. Our long term aim is to complete the census of MW GCs. The immediate goals are to estimate the astrophysical parameters, measuring their reddenings, extinctions, distances, total luminosities, proper motions, sizes, metallicities and ages. We use the near-IR VVVX survey database, in combination with Gaia DR2 optical photometry, and with the Two Micron All Sky Survey (2MASS) photometry. We report the detection of a heretofore unknown Galactic Globular Cluster at $RA =$ 14:09:00.0; $DEC=-$65:37:12 (J2000). We calculate a reddening of $E(J-K_s)=(0.3\pm 0.03)$ mag and an extinction of $A_{K_s}=(0.15\pm 0.01)$ mag for this new GC. Its distance modulus and corresponding distance were measured as $(m-M)=(15.93\pm0.03)$ mag and $D=(15.5\pm1.0)$ kpc, respectively. We estimate the metallicity and age by comparison with known GCs and by fitting PARSEC and Dartmouth isochrones, finding $[Fe/H]=(-0.70\pm0.2)$ dex and $t=(11.0\pm1.0)$ Gyr. The mean GC PMs from Gaia are $μ_{α^\ast}=(-4.68 \pm 0.47 )$ mas $yr^{-1}$ and $μ_δ=(-1.34 \pm 0.45)$ mas $yr^{-1}$. The total luminosity of our cluster is estimated to be $M_{Ks}=(-7.76\pm 0.5)$ mag. We have found a new low-luminosity, old and metal-rich globular cluster, situated in the far side of the Galactic disk, at $R_{G}=11.2$ kpc from the Galactic centre, and at $z=1.0$ kpc below the plane. Interestingly, the location, metallicity and age of this globular cluster are coincident with the Monoceros Ring (MRi) structure.

astro-ph.GA↗

arXiv2020

The VVV Infrared Variability Catalog (VIVA-I)

Thanks to the VISTA Variables in the Via Lactea (VVV) ESO Public Survey it is now possible to explore a large number of objects in those regions. This paper addresses the variability analysis of all VVV point sources having more than 10 observations in VVVDR4 using a novel approach. In total, the near-IR light curves of 288,378,769 sources were analysed using methods developed in the New Insight Into Time Series Analysis project. As a result, we present a complete sample having 44, 998, 752 variable star candidates (VVV-CVSC), which include accurate individual coordinates, near-IR magnitudes (ZYJHKs), extinctions A(Ks), variability indices, periods, amplitudes, among other parameters to assess the science. Unfortunately, a side effect of having a highly complete sample, is also having a high level of contamination by non-variable (contamination ratio of non-variables to variables is slightly over 10:1). To deal with this, we also provide some flags and parameters that can be used by the community to de-crease the number of variable candidates without heavily decreasing the completeness of the sample. In particular, we cross-identified 339,601 of our sources with Simbad and AAVSO databases, which provide us with information for these objects at other wavelegths. This sub-sample constitutes a unique resource to study the corresponding near-IR variability of known sources as well as to assess the IR variability related with X-ray and Gamma-Ray sources. On the other hand, the other 99.5% sources in our sample constitutes a number of potentially new objects with variability information for the heavily crowded and reddened regions of the Galactic Plane and Bulge. The present results also provide an important queryable resource to perform variability analysis and to characterize ongoing and future surveys like TESS and LSST.

astro-ph.SR↗

arXiv2020

VVV-WIT-01: highly obscured classical nova or protostellar collision?

A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 ($H-K_s=5.2$). It peaked before March 2010, then faded by $\sim$9.5 mag over the following two years. The 1.6--22 $μ$m spectral energy distribution in March 2010 was well fit by a highly obscured black body with $T \sim 1000$ K and $A_{K_s} \sim 6.6$ mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062$-$0.294. The chance projection probability is small for any single event ($p \approx 0.01$ to 0.02) which suggests a physical association, e.g. a collision between low mass protostars. However, black body emission at $T \sim 1000$ K is common in classical novae (especially CO novae) at the infrared peak in the light curve, due to condensation of dust $\sim$30--60 days after the explosion. Radio follow up with the Australia Telescope Compact Array (ATCA) detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to $p=0.13$ to 0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.

astro-ph.SR↗

arXiv2019

A Color-Excess Extinction map of the Southern Galactic disk from the VVV and GLIMPSE Surveys

An improved high-resolution and deep A$_{Ks}$ foreground dust extinction map is presented for the Galactic disk area within $295^{\circ} \lesssim l \lesssim 350^{\circ}$, $-1.0^{\circ} \lesssim b \lesssim +1.0^{\circ}$. At some longitudes the map reaches up to $|b|\sim2.25^{\circ}$, for a total of $\sim$148 deg$^2$. The map was constructed via the Rayleigh-Jeans Color Excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1', and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO's Vista Variables in the Vía Láctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). The VVV photometry penetrates $\sim$4 magnitudes fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.

astro-ph.GA↗

arXiv2018

A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?

We present the physical characterization of FSR 1758, a new large, massive object very recently discovered in the Galactic Bulge. The combination of optical data from the 2nd Gaia Data Release (GDR2) and the DECam Plane Survey (DECaPS), and near-IR data from the VISTA Variables in the V\'ıa Láctea Extended Survey (VVVX) led to a clean sample of likely members. Based on this integrated dataset, position, distance, reddening, size, metallicity, absolute magnitude, and proper motion of this object are measured. We estimate the following parameters: $α=17:31:12$, $δ=-39:48:30$ (J2000), $D=11.5 \pm 1.0$ kpc, $E(J-Ks)=0.20 \pm 0.03$ mag, $R_c=10$ pc, $R_t=150$ pc, $[Fe/H]=-1.5 \pm 0.3$ dex, $M_i < -8.6 \pm 1.0$, $μ_α = -2.85$ mas yr$^{-1}$, and $μ_δ = 2.55$ mas yr$^{-1}$. The nature of this object is discussed. If FRS 1758 is a genuine globular cluster, it is one of the largest in the Milky Way, with a size comparable or even larger than that of $ω$ Cen, being also an extreme outlier in the size vs. Galactocentric distance diagram. The presence of a concentration of long-period RR Lyrae variable stars and blue horizontal branch stars suggests that it is a typical metal-poor globular cluster of Oosterhoff type II. Further exploration of a larger surrounding field reveals common proper motion stars, suggesting either tidal debris or that FRS\,1758 is actually the central part of a larger extended structure such as a new dwarf galaxy, tentatively named as Scorpius. In either case, this object is remarkable, and its discovery graphically illustrates the possibility to find other large objects hidden in the Galactic Bulge using future surveys.

astro-ph.GA↗

arXiv2018

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - X. Three high-contrast systems with secondaries detected with IR spectroscopy

We present results of the combined photometric and spectroscopic analysis of three detached eclipsing binaries, which secondary components are not visible or very hard to identify in the optical spectra - ASAS J052743-0359.7, ASAS J065134-2211.5, and ASAS J073507-0905.7. The first one is a known visual binary ADS 4022, and we found that it is a quadruple system, composed of two spectroscopic binaries, one of which shows eclipses. None of the systems was previously recognized as a spectroscopic binary. We collected a number of high-resolution optical and IR spectra to calculate the radial velocities (RVs) and later combined them with MITSuME and ASAS photometry. The IR spectra were crucial for secure identification of the cooler components' lines. RV measurements were done with the TODCOR technique, and RV curves modelled with our own procedure V2FIT. Light curve modelling was performed with JKTEBOP and PHOEBE codes. Temperatures and metallicities of two systems were estimated from spectra. For the ADS 4022 system we also used the archival WDS data and new SOAR observations in order to derive the orbit of the visual pair for the first time. Ages were estimated by comparing our results with PARSEC isochrones. The eclipsing pair A052743 A ($P=5.27$ d) is composed of a 1.03(6) M$_\odot$, 1.03(2) R$_\odot$ primary and a 0.60(2) M$_\odot$, 0.59(2) R$_\odot$ secondary. The components of the $P=21.57$ d non-eclipsing pair B likely have masses in between the two eclipsing components, and both pairs are on a $\sim$188 yr orbit around their common centre of mass. The system A065134 ($P=8.22$ d) consists of a 0.956(12) M$_\odot$, 0.997(4) R$_\odot$ primary and a 0.674(5) M$_\odot$, 0.690(7) R$_\odot$ secondary. Finally, A073507 ($P=1.45$ d), which consists of a 1.452(34) M$_\odot$, 1.635(12) R$_\odot$ primary and a 0.808(13) M$_\odot$, 0.819(11) R$_\odot$ secondary, is likely a PMS system.

astro-ph.SR↗

arXiv2018

New Galactic Star Clusters Discovered in the Disk Area of the VVVX Survey

The "VISTA Variables in the Via Lactea eXtended (VVVX)" ESO Public Survey is a near-infrared photometric sky survey that covers nearly 1700 sq. deg towards the Galactic disk and bulge. It is well-suited to search for new open clusters, hidden behind dust and gas. The pipeline processed and calibrated Ks-band tile images of 40% of the disk area covered by VVVX was visually inspected for stellar over-densities. Then, we identified cluster candidates by examination of the composite JHKs color images. The color-magnitude diagrams of the cluster candidates are constructed. Whenever possible the Gaia DR2 parameters are used to calculate the mean proper motions, radial velocities, reddening and distances. We report the discovery of 120 new infrared clusters and stellar groups. Approximately, half of them (47%) are faint, compact, highly reddened, and they seem to be associated with other indicators of recent star formation, such as nearby Young Stellar Objects, Masers, H II regions or bubbles. The preliminary distance determinations allow us to trace the clusters up to 4.5 kpc, but most of the cluster candidates are centered at 2.2 kpc. The mean proper motions of the clusters, show that in general, they follow the disk motion of the Galaxy.

astro-ph.GA↗

arXiv2018

Measurement of shower development and its Molière radius with a four-plane LumiCal test set-up

A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Molière radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.

physics.ins-det↗

arXiv2017

Nucleosynthesis in 2D Core-Collapse Supernovae of 11.2 and 17.0 M$_{\odot}$ Progenitors: Implications for Mo and Ru Production

Core-collapse supernovae are the first polluters of heavy elements in the galactic history. As such, it is important to study the nuclear compositions of their ejecta, and understand their dependence on the progenitor structure (e.g., mass, compactness, metallicity). Here, we present a detailed nucleosynthesis study based on two long-term, two-dimensional core-collapse supernova simulations of a 11.2 M$_{\odot}$ and a 17.0 M$_{\odot}$ star. We find that in both models nuclei well beyond the iron group (up to $Z \approx 44$) can be produced, and discuss in detail also the nucleosynthesis of the p-nuclei $^{92,94}$Mo and $^{96,98}$Ru. While we observe the production of $^{92}$Mo and $^{94}$Mo in slightly neutron-rich conditions in both simulations, $^{96,98}$Ru can only be produced efficiently via the $ν$p-process. Furthermore, the production of Ru in the $ν$p-process heavily depends on the presence of very proton-rich material in the ejecta. This disentanglement of production mechanisms has interesting consequences when comparing to the abundance ratios between these isotopes in the solar system and in presolar grains.

astro-ph.SR↗

arXiv2017

Deconfinement to Quark Matter in Neutron Stars - The Influence of Strong Magnetic Fields

We use an extended version of the hadronic SU(3) non-linear realization of the sigma model that also includes quarks to study hybrid stars. Within this approach, the degrees of freedom change naturally as the temperature/density increases. Different prescriptions of charge neutrality, local and global, are tested and the influence of strong magnetic fields and the anomalous magnetic moment on the particle population is discussed.

astro-ph.HE↗