Intensity-corrected Herschel Observations of Nearby Isolated Low-mass Clouds*

Abstract

We present intensity-corrected Herschel maps at 100 µm, 160 µm, 250 µm, 350 µm, and 500 µm for 56 isolated low-mass clouds. We determine the zero-point corrections for Herschel PACS and SPIRE maps from the Herschel Science Archive (HSA) using Planck data. Since these HSA maps are small, we cannot correct them using typical methods. Here, we introduce a technique to measure the zero-point corrections for small Herschel maps. We use radial profiles to identify offsets between the observed HSA intensities and the expected intensities from Planck. Most clouds have reliable offset measurements with this technique. In addition, we find that roughly half of the clouds have underestimated HSA-SPIRE intensities in their outer envelopes relative to Planck, even though the HSA-SPIRE maps were previously zero-point corrected. Using our technique, we produce corrected Herschel intensity maps for all 56 clouds and determine their line-of-sight average dust temperatures and optical depths from modified black body fits. The clouds have typical temperatures of ∼ 14 − 20 K and optical depths of ∼ 10 −5 − 10 −3 . Across the whole sample, we find an anti-correlation between temperature and optical depth. We also find lower temperatures than what was measured in previous Herschel studies, which subtracted out a background level from their intensity maps to circumvent the zero-point correction. Accurate Herschel observations of clouds are key to obtain accurate density and temperature profiles. To make such future analyses possible, intensity-corrected maps for all 56 clouds are publicly available in the electronic version.

Periodic Eruptive Variability of the Isolated Pre-main-sequence Star V347 Aurigae

“…The millimeter imaging of Launhardt & Sargent (2001) identified a deeply embedded, ∼0.3 M e protostar with an edge-on disk forming within L1439. These authors suggested the cloud may be an extension of the Taurus-Auriga star-forming region (see also Sadavoy et al 2018).…”

Distortion of Magnetic Fields in BHR 71

“…To determine the basic physical properties of the BHR 71 core, we used the FIR data taken by the Herschel satellite. Sadavoy et al (2018) provided an intensity-corrected Herschel map of BHR 71, and a map at an optical depth of 353 GHz (τ 353GHz ) was included in their products. The map has 28 × 28 pixels with a pixel scale of 14 ′′ pixel −1 and resolution of 36.3 ′′ .…”

The Formation Conditions of the Wide Binary Class 0 Protostars within BHR 71

“…We started with the extended source map and utilized the tabulated beam correction, color correction, and aperture correction for a source with a spectral index of 3.5 and a temperature of 30 K. These are reasonable assumptions for a protostar as the SED peaks at ∼100 µm and the dust opacity spectral index will result in a spectral index between 3 and 4 in the sub-millimeter range. Our photometry are taken toward the region of compact emission toward the protostar locations and not from the entire extended core; thus, we do not need to worry about the proper zero-point flux calibration as in (Sadavoy et al 2018) 3. OBSERVATIONAL RESULTS The multitude of infrared and submillimeter data taken toward BHR71 are shown in Figures 1 & 2.…”

“…With these values, we estimate the Jeans length to be ∼8400 AU, which is much larger than the projected separation of IRS1 and IRS2. Lower temperatures were certainly possible prior to protostar formation (e.g., Stutz et al 2010;Sadavoy et al 2018) and higher densities as well, but an average density 10× higher is necessary to make the Jeans length comparable to the current protostar separation. Thus, thermal Jeans fragmentation is not clearly a favored mechanism on its own to form the binary system, and turbulent fragmentation remains the most likely candidate.…”