Astrophysical parameters of 14 open clusters projected close to the Galactic plane

Astrophysical parameters (\textit{age, reddening, distance, core and cluster radii}) of 14 open clusters (OCs) projected close to the Galactic plane are derived with 2MASS photometry. The OCs are Be 63, Be 84, Cz 6, Cz 7, Cz 12, Ru 141, Ru 144, Ru 172, FSR 101, FSR 1430, FSR 1471, FSR 162, FSR 178 and FSR 198. The OCs Be 63, Be 84, Ru 141, Ru 144, and Ru 172 are studied in more detail than in previous works, while the others have astrophysical parameters derived for the first time. The open clusters of the sample are located at $d_\odot=1.6-7.1$ kpc from the Sun and at Galactocentric distances $5.5-11.8$ kpc, with age in the range 10 Myr to 1.5 Gyr and reddening $E(B-V)$ in the range $0.19-2.56$ mag. The core and cluster radii are in the range $0.27-1.88$ pc and $2.2-11.27$ pc, respectively. Cz 6 and FSR 198 are the youngest OCs of this sample, with a population of pre-main sequence (PMS) stars, while FSR 178 is the oldest cluster.Comment: 11 pages, 14 figures - accepted by A&

Towards a census of the Galactic anticentre star clusters: colour-magnitude diagram and structural analyses of a sample of 50 objects

In this work we investigate the nature of 50 overdensities from the catalogue of Froebrich, Scholz, and Raftery (FSR) projected towards the Galactic anticentre, in the sector 160{\deg} \leq \ell \leq 200{\deg}. The sample contains candidates with |b| \leq 20{\deg} classified by FSR as probable open cluster (OC) and labelled with quality flags 2 and 3. Our main purpose is to determine the nature of these OC candidates and the fraction of these objects that are unknown OCs, as well as to derive astrophysical parameters (age, reddening, distance, core and cluster radii) for the clusters and to investigate the relationship among parameters. The analysis is based on 2MASS J, (J-H), and (J-Ks) colour-magnitude diagrams (CMDs), and stellar radial density profiles (RDPs) built with decontamination tools. The tools are a field star decontamination algorithm, used to uncover the cluster's intrinsic CMD morphology, and colour-magnitude filters to isolate stars with a high probability of being cluster members. Out of the 50 objects, 16 (32%) are star clusters. We show that 9 (18%) overdensities are new OCs (FSR 735, FSR 807, FSR 812, FSR 826, FSR 852, FSR 904, FSR 941, FSR 953, and FSR 955) and 7 (14%) are previously studied or catalogued OCs (KKC1, FSR 795, Cz 22, FSR 828, FSR 856, Cz 24, and NGC 2234). These are OCs with ages in the range 5 Myr to 1 Gyr, at distances from the Sun 1.28 \precnapprox d_Sun(kpc) \precnapprox 5.78 and Galactocentric distances 8.5 R_GC(kpc) \precnapprox 12.9. We also derive parameters for the previously analysed OCs Cz 22 and NGC 2234. Five (10%) candidates are classified as uncertain cases, and the remaining objects are probable field fluctuations.Comment: 14 pages, 15 figure

A possible sequential star formation in the giant molecular cloud G174+2.5

We investigate the nature of 14 embedded clusters (ECs) related to a group of four H II regions Sh2-235, Sh2-233, Sh2-232, and Sh2-231 in the giant molecular cloud G174 + 2.5. Projected towards the Galactic anticentre, these objects are a possible example of the collect and collapse scenario. We derive astrophysical parameters (age, reddening, distance, core and cluster radii) for the ECs and investigate the relationship among their parameters. Parameters are derived with field decontaminated 2MASS colour-magnitude diagrams (CMDs) and stellar radial density profiles (RDPs). The CMDs of these young clusters are characterised by a poorly-populated main sequence and a significant number of pre-main sequence stars, affected by differential reddening. The ECs are KKC 11, FSR 784, Sh2-235 E2, Sh2-235 Cluster, Sh2-233SE Cluster, BDSB 73, Sh2-235B Cluster, BDSB 72, BDSB 71, Sh2-232 IR, PCS 2, and the newly found clusters CBB 1 and CBB 2. We were able to derive fundamental parameters for all ECs in the sample. Structural parameters are derived for FSR 784, Sh2-235 Cluster and Sh2-235E2.Comment: 14 pages and 15 figures; MNRAS 201

Near-infrared photometry of globular clusters towards the Galactic bulge: Observations and photometric metallicity indicators

Indexación: Web of Science; Scopus.We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature.We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] ≳ -1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2 ≲ [M/H] ≲ 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stw243

UKIRT follow-up observations of the old open cluster FSR0358 (Kirkpatrick1)

We aim to characterise the properties of the stellar clusters in the Milky Way. Utilising an expectation-maximisation method we determined that the cluster FSR0358, originally discovered by J.D.Kirkpatrick, is the most likely real cluster amongst the cluster candidates from Froebrich et al.. Here we present new deep high resolution near infrared imaging of this object obtained with UKIRT. The analysis of the data reveals that FSR0358 (Kirkpatrick1) is a 5+-2Gyr old open cluster in the outer Milky Way. Its age, metallicity of Z=0.008 and distance from the Galactic Centre of 11.2kpc are typical for the known old open galactic clusters. So far six of the FSR cluster candidates have been identified as having an age above 5Gyr. This shows the significance of this catalogue in enhancing our knowledge of the oldest open clusters in the Galaxy.Comment: 8 pages, 1 table, 5 figures, accepted for publication by MNRAS, a version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

Anchors for the Cosmic Distance Scale: the Cepheids U Sgr, CF Cas and CEab Cas

New and existing X-ray, UBVJHKsW(1-4), and spectroscopic observations were analyzed to constrain fundamental parameters for M25, NGC 7790, and dust along their sight-lines. The star clusters are of particular importance given they host the classical Cepheids U Sgr, CF Cas, and the visual binary Cepheids CEa and CEb Cas. Precise results from the multiband analysis, in tandem with a comprehensive determination of the Cepheids' period evolution (dP/dt) from ~140 years of observations, helped resolve concerns raised regarding the clusters and their key Cepheid constituents. Specifically, distances derived for members of M25 and NGC 7790 are 630+-25 pc and 3.40+-0.15 kpc, respectively.Comment: To appear in Astronomy and Astrophysic

NGC2180: a disrupting open cluster

The spatial dependence of luminosity and mass functions of evolved open clusters is discussed in this work using J and H 2MASS photometry. The target objects are the overlooked open cluster NGC2180 and the intermediate-age open cluster NGC3680. We conclude that, although in an advanced dynamical state (mass segregated), NGC3680 does not present strong signs of dissolution. On the other hand, NGC2180 presents flat, eroded LFs throughout its structure, indicating that in addition to mass segregation, Galactic tidal stripping has been effective in depleting this cluster of stars. Accordingly, NGC2180 may be the missing link between evolved open clusters and remnants. We study both clusters in the context of dynamical states estimated from diagnostic-diagrams involving photometric and structural parameters. Both clusters are dynamically evolved systems. In particular, NGC2180 is closer to open cluster remnants than NGC3680.Comment: 9 pages, 8 figure

Anchors for the Cosmic Distance Scale: the Cepheid QZ Normae in the Open Cluster NGC 6067

Cepheids are key to establishing the cosmic distance scale. Therefore it's important to assess the viability of QZ Nor, V340 Nor, and GU Nor as calibrators for Leavitt's law via their purported membership in the open cluster NGC 6067. The following suite of evidence confirms that QZ Nor and V340 Nor are members of NGC 6067, whereas GU Nor likely lies in the foreground: (i) existing radial velocities for QZ Nor and V340 Nor agree with that established for the cluster (-39.4+-1.2 km/s) to within 1 km/s, whereas GU Nor exhibits a markedly smaller value; (ii) a steep velocity-distance gradient characterizes the sight-line toward NGC 6067, thus implying that objects sharing common velocities are nearly equidistant; (iii) a radial profile constructed for NGC 6067 indicates that QZ Nor is within the cluster bounds, despite being 20' from the cluster center; (iv) new BVJH photometry for NGC 6067 confirms the cluster lies d=1.75+-0.10 kpc distant, a result that matches Wesenheit distances computed for QZ Nor/V340 Nor using the Benedict et al. (2007, HST parallaxes) calibration. QZ Nor is a cluster Cepheid that should be employed as a calibrator for the cosmic distance scale.Comment: To appear in ApS

NTT follow-up observations of star cluster candidates from the FSR catalogue

We are conducting a large program to classify newly discovered Milky Way star cluster candidates from the list of Froebrich, Scholz & Raftery (2007). Here we present deep NIR follow-up observations from ESO/NTT of 14 star cluster candidates. We show that the combined analysis of star density maps and colour-colour/magnitude diagrams derived from deep near-infrared imaging is a viable tool to reliably classify new stellar clusters. This allowed us to identify two young clusters with massive stars, three intermediate age open clusters, and two globular cluster candidates among our targets. The remaining seven objects are unlikely to be stellar clusters. Among them is the object FSR1767 which has previously been identified as a globular cluster using 2MASS data by Bonatto et al. (2007). Our new analysis shows that FSR1767 is not a star cluster. We also summarise the currently available follow-up analysis of the FSR candidates and conclude that this catalogue may contain a large number of new stellar clusters, probably dominated by old open clusters.Comment: 24pages, 3tables, 40figures, Accepted for publication by MNRAS, A version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

Accumulation horizons and period-adding in optically injected semiconductor lasers

We study the hierarchical structuring of islands of stable periodic oscillations inside chaotic regions in phase diagrams of single-mode semiconductor lasers with optical injection. Phase diagrams display remarkable {\it accumulation horizons}: boundaries formed by the accumulation of infinite cascades of self-similar islands of periodic solutions of ever-increasing period. Each cascade follows a specific period-adding route. The riddling of chaotic laser phases by such networks of periodic solutions may compromise applications operating with chaotic signals such as e.g. secure communications.Comment: 4 pages, 4 figures, laser phase diagrams, to appear in Phys. Rev. E, vol. 7