Setting up of standard ultraviolet passbands with CCD detectors

Straižys, V.; Lazauskaite, R.

doi:10.1515/astro-1995-0108

Cited by 66 publications

(104 citation statements)

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“…The ratio E(J − H)/E(H − K s ) may be inferred from all stars observed along the line of sight. A median (after making a 1.5σx clip) yields E(J − H)/E(H − K s ) = 2.20 ± 0.06(σx) ± 0.37(σ), which is far in excess of the various values for the inner Galaxy listed in Table 1 Straižys & Lazauskaitė (2009) in their analysis of the reddening law throughout the inner Galaxy. The reddening law determined was subsequently employed to interpret the JHK s CMDs.…”

Section: Extinctionmentioning

confidence: 80%

“…σ divided by the square root of the sample size. The aforementioned mean reddenings were inferred from the intrinsic BV JH colours of Turner (1989) and Straižys & Lazauskaitė (2009), so as to provide an independent check on the extinction estimates determined from the intrinsic parameters of Schmidt-Kaler (1982) and Koornneef (1983) in the preceding paragraph. The mean colour excess inferred from the spectroscopic observations for stars in Danks 1 is: E(J − K s ) = 1.63 ± 0.05(σx) ± 0.21(σ), E(J − H) = 1.07 ± 0.04(σx) ± 0.15(σ) and E(B − V) = 2.68 ± 0.06(σx) ± 0.27(σ).…”

Section: Extinctionmentioning

confidence: 99%

“…The results are tied to the intrinsic parameters of Schmidt-Kaler (1982) and Koornneef (1983), since R K s was derived using these studies. Straižys & Lazauskaitė (2009) supply intrinsic colours only. The parameters derived are consistent, within the uncertainties, using either dataset.…”

Section: Extinctionmentioning

confidence: 99%

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Massive open star clusters using the VVV survey

Chené

Borissova

Clarke

et al. 2012

A&A

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Context. The ESO Public Survey "VISTA Variables in the Vía Láctea" (VVV) provides deep multi-epoch infrared observations for unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. Aims. The VVV observations will foster the construction of a sample of Galactic star clusters with reliable and homogeneously derived physical parameters (e.g., age, distance, and mass, etc.). In this first paper in a series, the methodology employed to establish cluster parameters for the envisioned database are elaborated upon by analysing four known young open clusters: Danks 1, Danks 2, RCW 79, and DBS 132. The analysis offers a first glimpse of the information that can be gleaned from the VVV observations for clusters in the final database. Methods. Wide-field, deep JHK s VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results. Results are inferred from VVV near-infrared photometry and numerous low resolution spectra (typically more than 10 per cluster). The high quality of the spectra and the deep wide-field VVV photometry enables us to precisely and independently determine the characteristics of the clusters studied, which we compare to previous determinations. An anomalous reddening law in the direction of the Danks clusters is found, specifically E(J − H)/E(H − Ks) = 2.20 ± 0.06, which exceeds published values for the inner Galaxy. The G305 star forming complex, which includes the Danks clusters, lies beyond the Sagittarius-Carina spiral arm and occupies the Centaurus arm. Finally, the first deep infrared colour-magnitude diagram of RCW 79 is presented, which reveals a sizeable pre-main sequence population. A list of candidate variable stars in G305 region is reported. Conclusions. This study demonstrates the strength of the dataset and methodology employed, and constitutes the first step of a broader study which shall include reliable parameters for a sizeable number of poorly characterised and/or newly discovered clusters.Key words. open clusters and associations: general -infrared: stars -surveys IntroductionIt is commonly accepted that the majority of stars with masses ≥0.50 M form in clustered environments (e.g. than half of these clusters have actually been studied, and this subset suffers from further selection biases. Extending this current sample towards the Milky Way's highly obscured central region would provide unique insight into the formation, evolution, and dissipation of open clusters in the Galactic environment. To achieve this goal, we are using the unprecedented deep infrared data from the VISTA Variables in the Vía Láctea (VVV) survey (Minniti et al. 2010;Saito et al. 2012), one of the six ESO Public Surveys operating on the new 4-m Visible and Infrared Survey Telescope for Astronomy (VISTA). We are in the process of building a large sample of star clusters (including many discovered by our group; Borissova et al. 2011; Bonatto et al., in prep.), that are practically invisible in th...

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Section: Extinctionmentioning

confidence: 80%

Section: Extinctionmentioning

confidence: 99%

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Massive open star clusters using the VVV survey

Chené

Borissova

Clarke

et al. 2012

A&A

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“…The intrinsic H−K colour for O to A type stars is about −0.1 to 0.05 (Straižys & Lazauskaitė 2009), therefore the measured colour is almost entirely caused by extinction. Schödel et al (2010) and Fritz et al (2011) (Schödel et al 2010).…”

Section: Distribution Of Young Starsmentioning

confidence: 89%

Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster

Feldmeier

Neumayer

Seth

et al. 2014

A&A

131

179

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Context. Within the central 10 pc of our Galaxy lies a dense cluster of stars. This nuclear star cluster forms a distinct component of the Galaxy, and similar nuclear star clusters are found in most nearby spiral and elliptical galaxies. Studying the structure and kinematics of nuclear star clusters reveals the history of mass accretion and growth of galaxy nuclei and central massive black holes. Aims. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve the cluster on sub-parsec scales. This makes the Milky Way nuclear star cluster a reference object for understanding the formation of all nuclear star clusters. Methods. We have used the near-infrared long-slit spectrograph ISAAC (VLT) in a drift-scan to construct an integral-field spectroscopic map of the central ∼9.5 × 8 pc of our Galaxy, and six smaller fields out to 19 pc along the Galactic plane. We use this spectroscopic data set to extract stellar kinematics both of individual stars and from the unresolved integrated light spectrum. We present a velocity and dispersion map from the integrated light spectra and model these kinematics using kinemetry and axisymmetric Jeans models. We also measure radial velocities and CO bandhead strengths of 1375 spectra from individual stars. Results. We find kinematic complexity in the nuclear star clusters radial velocity map including a misalignment of the kinematic position angle by 9 • counterclockwise relative to the Galactic plane, and indications for a rotating substructure perpendicular to the Galactic plane at a radius of 20 or ∼0.8 pc. We determine the mass of the nuclear star cluster within r = 4.2 pc to (1.4 +0.6 −0.7 ) × 10 7 M . We also show that our kinematic data results in a significant underestimation of the supermassive black hole (SMBH) mass. Conclusions. The kinematic substructure and position angle misalignment may hint at distinct accretion events. This indicates that the Milky Way nuclear star cluster grew at least partly by the mergers of massive star clusters. Compared to other nuclear star clusters, the Milky Way nuclear star cluster is on the compact side of the r eff − M NSC relation. The underestimation of the SMBH mass might be caused by the kinematic misalignment and a stellar population gradient. But it is also possible that there is a bias in SMBH mass measurements obtained with integrated light, and this might affect SMBH mass determinations of other galaxies.

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“…For the red (super)giants, we use the calibration of Straižys & Lazauskaitė (2009), which uses 2MASS colors. For the blue stars, we use the same calibration, assuming that giants have the same colors as main-sequence stars.…”

Section: Infrared Extinctionmentioning

confidence: 99%

The Young Open Cluster Berkeley 55

Negueruela

Marco

2012

The Astronomical Journal

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We present UBV photometry of the highly reddened and poorly studied open cluster Berkeley 55, revealing an important population of B-type stars and several evolved stars of high luminosity. Intermediate-resolution far-red spectra of several candidate members confirm the presence of one F-type supergiant and six late supergiants or bright giants. The brightest blue stars are mid-B giants. Spectroscopic and photometric analyses indicate an age 50 ± 10 Myr. The cluster is located at a distance d ≈ 4 kpc, consistent with other tracers of the Perseus Arm in this direction. Berkeley 55 is thus a moderately young open cluster with a sizable population of candidate red (super)giant members, which can provide valuable information about the evolution of intermediate-mass stars.

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Setting up of standard ultraviolet passbands with CCD detectors

Cited by 66 publications

References 0 publications

Massive open star clusters using the VVV survey

Massive open star clusters using the VVV survey

Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster

The Young Open Cluster Berkeley 55

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