Context : The availability of submillimeter dust emission data in an unprecedented number of bands provides us with new opportunities to investigate the properties of interstellar dust in nearby clouds .

Aims : The nearby Pipe Nebula is an ideal laboratory to study starless cores .
We here aim to characterize the dust properties of the FeSt 1-457 core , as well as the relation between the dust and the dense gas , using Herschel , Planck , 2MASS , ESO Very Large Telescope , APEX- Laboca , and IRAM 30m data .

Methods : We derive maps of submillimeter dust optical depth and effective dust temperature from Herschel data that were calibrated against Planck .
After calibration , we then fit a modified blackbody to the long-wavelength Herschel data , using the Planck -derived dust opacity spectral index \beta , derived on scales of 30 ^ { \prime } ( or \sim 1 pc ) .
We use this model to make predictions of the submillimeter flux density at 850 \mu m , and we compare these in turn with APEX- Laboca observations .
Our method takes into account any additive zeropoint offsets between the Herschel / Planck and Laboca datasets .
Additionally , we compare the dust emission with near-infrared extinction data , and we study the correlation of high-density–tracing N _ { 2 } H ^ { + } emission with the coldest and densest dust in FeSt 1-457 .

Results : A comparison of the submillimeter dust optical depth and near-infrared extinction data reveals evidence for an increased submillimeter dust opacity at high column densities , interpreted as an indication of grain growth in the inner parts of the core .
Additionally , a comparison of the Herschel dust model and the Laboca data reveals that the frequency dependence of the submillimeter opacity , described by the spectral index \beta , does not change .
A single \beta that is only slightly different from the Planck -derived value is sufficient to describe the data , \beta = 1.53 \pm 0.07 .
We apply a similar analysis to Barnard 68 , a core with significantly lower column densities than FeSt 1-457 , and we do not find evidence for grain growth but also a single \beta .
Finally , our previously reported finding of a correlation of N _ { 2 } H ^ { + } emission with lower effective dust temperatures is confirmed for FeSt 1-457 in mapping observations .

Conclusions : While we find evidence for grain growth from the dust opacity in FeSt 1-457 , we find no evidence for significant variations in the dust opacity spectral index \beta on scales 0.02 < x < 1 pc ( or 36 ^ { \prime \prime } < x < 30 ^ { \prime } ) .
The correction to the Planck -derived dust \beta that we find in both cases is on the order of the measurement error , not including any systematic errors , and it would thus be reasonable to directly apply the dust \beta from the Planck all-sky dust model .
As a corollary , reliable effective temperature maps can be derived which would be otherwise affected by \beta variations .
Finally , we note that the angular resolution of extinction maps for the study of nearby starless cores remains unsurpassed .