High angular resolution spectroscopic and polarimetric imaging of the galactic center in the near-infrared

Eckart, A.; Genzel, R.; Hofmann, R.; Sams, B.; Tacconi-Garman, L. E.

doi:10.1086/187880

Cited by 110 publications

(108 citation statements)

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“…A comparison to the values presented in Eckart et al (1995) reveals considerable deviations: only 47% of the 32 sources found both in the older study and the new dataset show an agreement in polarization degree within 3σ or less. 63% of the sources show a 3σ agreement for the polarization angles.…”

Section: Comparison To Previous Resultsmentioning

confidence: 68%

“…This still represents an increase by a factor of 4 compared to the sources in the same FOV for which Eckart et al (1995) determined the polarization (∼30 sources in this area, while Ott et al (1999) did not cover this region at all).…”

Section: Ks-band Polarizationmentioning

confidence: 85%

“…Specifically, sources embedded in the Northern Arm and other bow-shock sources show signs of intrinsic polarization, with IRS 21 showing the strongest total Ks-band polarization of a bright GC source detected to date (Eckart et al 1995;Ott et al 1999, ∼10-16% at 16 • ).…”

Section: Introductionmentioning

confidence: 93%

“…More than a decade later, higher resolution observations (0.25 ) enabled Eckart et al (1995) to increase the number of polarimetrically observed GC sources dramatically (160 sources in the central 13 × 13 , only Ks-band). In a follow-up study, Ott et al (1999) examined ∼40 bright sources in the central 20 × 20 at 0.5 resolution.…”

Section: Introductionmentioning

confidence: 99%

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

Witzel

Schödel

Eckart

2013

A&A

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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.

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Section: Comparison To Previous Resultsmentioning

confidence: 68%

Section: Ks-band Polarizationmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Witzel

Schödel

Eckart

2013

A&A

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show abstract

“…2 for an overview of the bright bow-shock sources in the central 20 ) show signs of intrinsic polarization. Among these objects, IRS 21 shows the strongest total Ks-band polarization of a bright GC source detected to date (Eckart et al 1995;Ott et al 1999, ∼10−16% at 16 • ). Tanner et al (2002) described IRS 21 as a bow-shock most likely created by a mass-losing Wolf-Rayet star.…”

Section: Introductionmentioning

confidence: 99%

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

Witzel

Schödel

Eckart

et al. 2011

A&A

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Context. The Galactic center offers unique opportunities to study stellar and bow-shock polarization effects in a dusty environment. Aims. The goals of this work are to provide near-infrared (NIR) polarimetry of the stellar sources in the central parsec at the resolution of an 8 m telescope for the first time, along with new insights into the nature of the known bright bow-shock sources. Methods. We use adaptive-optics assisted observations obtained at the ESO VLT in the H-and Ks-band, applying both high-precision photometric methods specifically developed for crowded fields and a newly established polarimetric calibration for NACO to produce polarization maps of the central 3 × 19 , in addition to spatially resolved polarimetry and a flux variability analysis on the extended sources in this region. Results. We find foreground polarization mainly parallel to the Galactic plane, with average values of (4.6 ± 0.6)% at 26 • ± 6 • (Ks-band) and (9.3 ± 1.3)% at 20 • ± 6 • (H-band) in the center of the field-of-view (FOV). Farther away from the center, we find higher polarization degrees and steeper polarization angles: (7.5 ± 1.0)% at 11 • ± 6 • (Ks-band) and (12.1 ± 2.1)% at 13 • ± 6 • (H-band). p H /p Ks peaks at 1.9 ± 0.4, corresponding to a power law index for the wavelength dependency of α = 2.4 ± 0.7. These values also vary over the FOV, with higher values in the center. This is indicative of the influence of local effects on the total polarization, possibly dichroic extinction by Northern Arm dust. The two extended sources IRS 21 and 1W show similar intrinsic polarization degrees of 6.1 resp. 7.8% (Ks) and 6.9 (H, only 1W) at polarization angles coincident with previous NIR and mid-infrared (MIR) findings, both in total and spatially resolved. The spatial polarization pattern of both sources points to scattering on aligned elongated dust grains as the major source of intrinsic polarization, and matches the known orientation of the magnetic field. Our data also allow us to separate the bow shock of IRS 21 from the central source for the first time in the Ks-band, finding the apex north of the central source and determining a standoff distance of ∼400 AU, which matches previous estimates. This source also shows a ∼50% increase in flux in the NIR over several years.

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Massive Stars and the Creation of our Galactic Center

Figer¹

2003

Proceedings of the Galactic Center Workshop 2002

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Our Galactic Center hosts over 10% of the known massive stars in the Galaxy. The majority of these stars are located in three particularly massive clusters that formed within the past 5 Myr. While these clusters are extraordinary, their formation repesents about half of the total inferred star formation rate in the Galactic Center. There is mounting evidence that the clusters are just present-day examples of the hundreds of such similar clusters that must have been created in the past, and whose stars now comprise the bulk of all stars seen in the region. I discuss the massive stellar content in the Galactic Center and present a new analysis that suggests that effects of continuous star formation in the Galactic Center can be seen in the observed luminosity functions newly-obtained HST/NICMOS and Gemini AO data.

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High angular resolution spectroscopic and polarimetric imaging of the galactic center in the near-infrared

Cited by 110 publications

References 0 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

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

Massive Stars and the Creation of our Galactic Center

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