Herschel-HIFI News

Submitted by Sylvie Beaulieu, Herschel-HIFI Instrument Support Scientist
(Cassiopeia – Summer/Été 2015)
Herschel_spacecraft_artist410

Herschel Interactive Processing Environment (HIPE)

HIPE 13.0 is the latest release, and HIFI_CAL_22_0 is the latest Calibration Tree. You are invited to visit ‘What’s New in HIPE’ for the changes in this new release. Additional information can be found in ‘HIFI Instrument and Calibration’

Herschel Science Archive (HSA)

The current ‘Herschel Science Archive’ is v.6.2.1. and has been released on 2 June 2015. Herschel data are 100% public domaine.

University of Waterloo Group News

Since the last publication of our newsletter, we saw the departure of instrument support scientist
Carolyn McCoey who recently gave birth to a beautiful girl. Carolyn was with the Herschel project
for nearly 8 years.

We also bid farewell to our HIFI system architect Kevin Edwards who was with the project for nearly
10 years. The group wishes to thank Carolyn and Kevin for their tremendous good work, they will be
missed greatly.

Please note that the Herschel-HIFI Waterloo group will cease operation by the 31st of March 2016.
Although no support will be available from that date via the Waterloo group, we will try to maintain
the webpage live, and as up-to-date as it is possible to do so.

The Herschel Science Centre, along with the Instrument Control Centres (HIFI, PACS, and SPIRE)
are in the process of implementing a documentation repository which will be known as the Herschel
Explanatory Legacy Library (HELL). This repository will be composed of the Mission and Satellite
Overview manual, the instruments handbooks, the instruments data reduction guides, as well as
technical and tests reports, and any documents that each ICC will want to provide for Legacy.

Permanent links to the ESA Herschel Project and to the Herschel Explanatory Legacy Library (HELL)
will be available through our webpage.

What’s New in HIPE 13

Pointing in all observations

A new approach to pointing reconstruction has been implemented in HIPE 13 by introducing additional correction
based on the gyroscope information. For the HIFI data, such a correction will be applied in a conditional fashion depending on a quality figure computed for each individual observation. The new pointing reconstruction will not apply to under-performing cases, and those latter will still use the pointing files used back in HIPE 12. Details about the new attitude reconstruction, and the way it is approached and may impact the HIFI data, can be found in these two documents: Pointing information and memo.

Electrical Standing Wave in Bands 6 and 7

From HIPE 13 onward, observations in bands 6 and 7 will automatically be corrected from the Electrical Standing
Wave affecting those data. The correction is based on an optimised fit to the baseline artefact stored in the
HIFI calibration files and applied by the pipeline. This also means that the optimum solution may not necessarily completely correct the standing wave. Note that the continuum present in band 6 and 7 data can only be fully trusted if the Electrical Standing Wave is corrected. Refined solutions will be provided on a case by case basis in HIPE 14. For instructions on how to benefit from this reprocessing and see the typical improvement expected in the data, please refer to section 11.4 of the HIFI Data Reduction Guide.

Spectral Scan Observations

The reprocessing of spectral scans in HIPE 13 will make use of optimised mask tables for spurs and unruly baseline ranges. This will result in improved deconvolved solutions at the Level 2.5. In order to benefit from this update you should reprocess your data from Level 0 with the new calibration tree (see section 5.4 of the HIFI Data Reduction Guide).

Calibrated OFF position spectra (any mode)

In HIPE 13, the data used in the OFF positions will be processed up to an equivalent Level 2 calibration (both in intensity and frequency) and can therefore be directly compared to the ON-target data. Details about the peculiarity of each OFF spectra can be found in the cookbooks (see chapter 2 of the HIFI Data Reduction Guide). In order to generate those spectra, you need to reprocess the data from the Level 1, and can work from the calibration tree present in the data processed with HIPE 12.1.

Single Point and Spectral Mapping Modes

The Level 2.5 products in these modes have been optimised by stitching the respective spectrometer subbands. In maps, for example, this will result in a smaller number of cubes. More details can be found in section 4.6 of the HIFI Data Reduction Guide.

Feature Story

Congratulations to recent PhD graduate Scott Jones (working with Dr. Martin Houde, Western Ontario)
who used HIFI data for part of his thesis.

Thesis abstract

Star formation is a fundamental process in the evolution of the cosmos. Yet given the abundance
of stellar constituents, it remains preeminent as to why the number of stars is not correspondingly
large. If we cannot satisfactorily explain how stars are formed, then many further avenues of research
are hindered.

This thesis furthers means to probe one of the foremost theories as to the relative lack of stars, interstellar
magnetic fields. These fields have been observationally verified on multiple scales. I will use the most direct
method to probe magnetic fields in known star-forming regions, polarization, at millimetre/submillimetre wavelengths. In particular, I will focus on the effect that magnetic fields have on the emission produced by rotational molecular transitions.

Much of the background behind the study of magnetic fields, and their deduction through submillimetre polarimetry, will be developed in Chapter 1. Here I provide an overview of not only the role that magnetic fields may play in star formation, but also the competing theories of turbulence and magnetohydrodynamic waves. The various manifestations of polarization will also be covered, including polarized molecular transitions.

Chapter 2 will look at one of the most well-studied star-forming regions, Orion KL, through observations of a newly discovered water maser transition at 620.701 GHz. Interstellar masers allow different environments to be probed, regions where more complex activity has created a population imbalance between rotational energy levels.

The remaining two chapters will present methods and data from the Four-Stokes- Parameter Spectral-Line Polarimeter at the Caltech Submillimeter Observatory. I will look at considerations that must be made when a small map is collected by way of quantifying the amount of instrumental polarization. Spurious polarization signals may pervade the outer edges of the telescope beam, leading to a misrepresentation of the true amount of source polarization. Chapter 3 details the methods involved in removing sidelobes plus the other sources of instrumental polarization, while Chapter 4 goes on to present the actual data to which these techniques have been applied. The data itself is of the molecular transition 12CO (J = 2 -> 1), prominent within the protostellar source OMC-2 FIR 4.

Publications

  1. Jones, S. C., Houde, M. and Hezareh, T. 2015, ApJ, to be submitted “The Detection of Non-Zeeman Circular Polarization of CO Rotational Lines in OMC-2 FIR 4”
  2. Jones, S. C., Houde, M., Harwit, M., Kidger, M., Kraus, A., McCoey, C., Marston, A., Melnick, G., Menten, K.M., Morris, P., Teyssier, D. and Tolls, V. 2014, A&A, 567, A31 “Polarisation observations of H2 O JK−1 K1 = 532 − 441 620.701 GHz maser emission with Herschel/HIFI in Orion KL”

Conferences, workshops and webinars related to Herschel

The University of Waterloo Herschel-HIFI Support Group is committed to assist you with accessing data through the Herschel Science Archive (HSA) and in using the Herschel Interactive Processing Environment (HIPE) to process your data. Please do not hesitate to contact us. Our webpage has a dedicated page on Data Processing.

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