Adaptive-optics assisted near-infrared polarization measurements of sources in the Galactic center

Witzel, G.; Schödel, R.; Eckart, A.; Bremer, M.; Mužić, K.

doi:10.1051/0004-6361/201117300

Cited by 12 publications

(76 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This technique was used to measure the fluxes of the 143 visible sources in the observed FOV of 8.6 × 25 . Compared to the Ks-band data presented in Buchholz et al (2011), the number of detected sources per arcsec 2 is lower by a factor of ∼6. This illustrates the much lower depth and worse data quality of the 2011 data.…”

Section: K S-bandcontrasting

confidence: 63%

“…Compared to the data presented in Buchholz et al (2011), our new observations cover a much greater FOV, at the price of a lower depth. The low data quality of the Ks-band data further limits this study to the brighter sources in the field.…”

Section: Observationmentioning

confidence: 53%

“…Figure 3 shows the resulting Ks-band luminosity function. Accoridngly, we estimate the depth of the new observations as ∼14 mag, which is shallower by 1.5 mag than the data used in Buchholz et al (2011).…”

Section: K S-bandmentioning

confidence: 71%

“…Using observations at even higher resolution, Buchholz et al (2011) presented H-and Ks-band polarimetry on 163 (H) respectively 194 (Ks) sources in the central 3 × 19 (with an additional FOV in the Ks-band that was rotated by 45 • containing 186 sources, see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…The marked areas denote the polarimetric FOVs: white indicates Ks-band, green Lp-band and blue H-band. The H-band (H1, see Table 1 and the two southern Ks-band FOVs (K1, K2) have been presented in Buchholz et al (2011), while the northern Ks-band (K3) and the Lp-band (L1) FOV are examined in this study.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

Witzel

Schödel

Eckart

2013

A&A

Self Cite

View full text Add to dashboard Cite

Context. Infrared observations of the Galactic center (GC) provide a unique opportunity to study stellar and bow-shock polarization effects in a dusty environment. Aims. The goals of this work are to present new Ks-and Lp-band polarimetry on an unprecedented number of sources in the central parsec of the GC, thereby expanding our previous results in the H-and Ks-bands. Methods. We use AO-assisted Ks-and Lp-band observations, obtained at the ESO VLT. High precision photometry and the new polarimetric calibration method for NACO allow us to map the polarization in a region of 8 × 25 (Ks) resp. 26 × 28 (Lp). These are the first polarimetric observations of the GC in the Lp-band in 30 years, with vastly improved spatial resolution compared to previous results. This allows resolved polarimetry on bright bow-shock sources in this area for the first time at this wavelength. Results. We find foreground polarization to be largely parallel to the Galactic plane (Ks-band: 6.1% at 20 • , Lp-band: 4.5% at 20 • ), in good agreement with our previous findings and with older results. The previously described Lp-band excess in the foregound polarization towards the GC could be confirmed here for a much larger number of sources. The bow-shock sources contained in the FOV seem to show a different relation between the polarization in the observed wavelength bands than what was determined for the foreground. This points to the different relevant polarization mechanisms. The resolved polarization patterns of IRS 5 and 10W match the findings we presented earlier for IRS 1W. Additionally, intrinsic Lp-band polarization was measured for IRS 1W and 21, as well as for other, less prominent mid-infrared-excess sources (IRS 2S, 2L, 5NE). The new data offer support for the presumed bow-shock nature of several of these sources (1W, 5, 5NE, 10W, 21) and for the model of bow-shock polarization presented in our last work.

show abstract

Section: K S-bandcontrasting

confidence: 63%

Section: Observationmentioning

confidence: 53%

Section: K S-bandmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

Witzel

Schödel

Eckart

2013

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8

Rauch

Mužić

Eckart

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

Context. IRS 8 offers the possibility to study unique bow shock properties and polarization features in the dusty environment at the Galactic center. Aims. We aim to gain insight into the properties of the surrounding material of the bow shock source IRS 8, based on the measured polarization distribution along its extended feature. Bow shock models enable a relative positioning of its central star with respect to the northern arm and Sagittarius A*. Methods. The analysis is based on polarimetric K S -band and nonpolarimetric L -and N-band data obtained with the adaptive-optics assisted instrument NAOS/CONICA (K S -and L -band) and the mid-infrared imager/spectrograph VISIR (N-band) at the ESO Very Large Telescope. A polarization map covering an area of ∼31.9 × 8.2 at the position of IRS 8 was obtained using high-precision photometric methods, together with a polarimetric calibration specified for NACO. In addition, simulated L -band bow shock models are presented, which allow a positioning of IRS 8 with respect to the interaction medium of the northern arm.Results. This work presents interstellar dust properties for the northern arm in the vicinity of a bow shock, as well as a threedimensional positioning of IRS 8 with respect to the northern arm and Sagittarius A*. The presented polarization maps for the Galactic center source IRS 8 show a total intrinsic polarization degree of 3.3% at 13 • east of north, measured on nondeconvolved images, and 4.3% at 19 • on Lucy-Richardson deconvolved images. Analysis of the polarization distribution along the bow shock reveals a polarization pattern as it would be produced by absorption on aligned grains and shows a decreasing polarization degree towards the apex of the bow shock. Current literature provides a mean electron density for IRS 8. The comparison of this value with properties of simulated polarization maps in a circumstellar environment, which are capable of multiple scattering, leads to the conclusion that multiple scattering events reduce the degree of polarization at the apex of the bow shock. Additionally, bow shock models that allow relative positioning of IRS 8 with respect to the northern arm and Sagittarius A* are presented. The results indicate that its central star is located closer towards the observer than the northern arm.

show abstract

Properties of bow-shock sources at the Galactic center

Sánchez-Bermúdez

Schödel

Alberdi

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. There exists an enigmatic population of massive stars around the Galactic center (GC) that were formed some Myr ago. A fraction of these stars has been found to orbit the supermassive black hole, Sgr A*, in a projected clockwise disk-like structure, which suggests that they were formed in a formerly existing dense disk around Sgr A*. Aims. We focus on a subgroup of objects, the extended, near-infrared (NIR) bright sources IRS 1W, IRS 5, IRS 10W, and IRS 21, that have been suggested to be young, massive stars that form bow shocks through their interaction with the interstellar medium (ISM). Their nature has impeded accurate determinations of their orbital parameters. We aim at establishing their nature and kinematics to test whether they form part of the clockwise disk. Methods. We performed NIR multiwavelength imaging with NACO/VLT using direct adaptive optics (AO) and AO-assisted sparse aperture masking (SAM). We introduce a new method for self-calibration of the SAM point spread function in dense stellar fields. The emission mechanism, morphology, and kinematics of the targets were examined via 3D models, combined with existing models of the gas flow in the central parsec.Results. We confirm previous findings that IRS 21, IRS 1W, and IRS 5 are bow-shocks created by the interaction between mass-losing stars and the interstellar gas. The nature of IRS 10W remains unclear. Our modeling shows that the bow-shock emission is caused by thermal emission, while the scattering of stellar light does not play a significant role. IRS 1W shows a morphology that is consistent with a bow shock produced by an anisotropic stellar wind or by locally inhomogeneous ISM density. Our best-fit models provide estimates of the local proper motion of the ISM in the Northern Arm that agree with previously published models that were based on radio interferometry and NIR spectroscopy. Assuming that all of the sources are gravitationally tied to Sagittarius A*, their orbital planes were obtained via a Monte Carlo simulation. Conclusions. Our sources appear to be Wolf-Rayet stars associated to the last starburst at the GC. Our orbital analysis suggests that they are not part of any of the previously suggested coherent stellar structures, in particular the clockwise disk. We thus add more evidence to recent findings that a large proportion of the massive stars show apparently random orbital orientations, suggesting either that not all of them were formed in the clockwise disk, or that their orbits were randomized rapidly after formation in the disk.

show abstract

Adaptive-optics assisted near-infrared polarization measurements of sources in the Galactic center

Cited by 12 publications

References 56 publications

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8

Properties of bow-shock sources at the Galactic center

Contact Info

Product

Resources

About

Adaptive-optics assisted near-infrared polarization measurements of sources in the Galactic center

Cited by 12 publications

References 56 publications

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

Ks- andLp-band polarimetry on stellar and bow-shock sources in the Galactic center

A peek behind the dusty curtain:KS-band polarization photometry and bow shock models of the Galactic center source IRS 8

Properties of bow-shock sources at the Galactic center

Contact Info

Product

Resources

About

A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8