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First results from data obtained on Aug 12 - 17

The data obtained during the NIKA2 run 67 (i.e. flux calibration scans & beam maps on Uranus, Neptune, Mars [app. size ~6.1"], and Mercury [app. size ~11"], as well as the secondary flux standards NGC7027, MWC349, CRL618, and CRL2688) after recoating M1 were preliminarily reprocessed a few days after the observations with PIIC-QL and the DAFs version in force on the dates indicated above.

In addition, we have reprocessed the same kind of maps for the source mentioned above, observed during the runs NIKA2 run 66 (2024/03/5-19; Winter 23; after servo-control upgrading and before painting works) and NIKA2 run 63 (2023/01/10-31; Winter 22; it was the last NIKA2 pool week before servo-control upgrading) for comparison purposes. Comprehensive main beam (MB) retrieved flux fraction plots, containing pointing and in-focus scans of the selected and other flux calibration sources for these runs (and soon for the case of the current run) can be found in the PIIC calibration summary and figures document. It is worth noting that the lack of lateral focus correction (carried out on MJD=60385) affects calibration data collected during the N2R66. This correction has been adopted for N2R67.

Mean MB & aperture (AP) retrieved flux fractions [%] per array for the recent tests and selected previous runs are summarised in the following table. Data from Mercury have been excluded from the statistics. Plots of that variable as a function of MJD [days], UT time of day [h], Elevation [deg], and FWHM [arcsec] (as sqrt[FWHM(minor axis)*FWHM(major axis)]) are given below.

(*) scans on Mercury are excluded from statistics in this Table

• MB flux vs. MJD (Red line in the N2R66 plots marks the time when a lateral focus correction was implemented):

• MB flux vs. UT (Dashed and solid yellow lines mark the mean times of civil and astronomical twilights, respectively):

• MB flux vs. Elevation:

• MB flux vs. FWHM:

• The average (dispersion) of preliminary MB retrieved flux for data gathered in the current run is slightly smaller (higher) than the expected values if we use N2R63 data as a reference. MB flux of sources observed after ~1h-exposition of the telescope to solar radiation (previous refocusing) are indistinguishable from those obtained at the rest of the times.

• Calibration data are well distributed in elevation for all NIKA2 runs referred (~20 < El. [deg] < 80, in the case of N2R67).

• The MB retrieved fluxes corresponding to observations made after sunset during N2R67 seem slightly smaller than the rest. However, those data were obtained at elevations < 30 or > 65 deg. We ignore what is the nature of the correction for gain-elevation (cf. Greve et al. 1998) in the computation of such fluxes.

• We did not find substantial dependences of FWHM with the UT time of day (not represented). More observations would be required, especially those to fill the gap between afternoon and evening. However, it is also true that the seasonal conditions of recent observations are not representative of the science pools.

As complementary data, the table below contains the mean values and deviations of the main beam (MB) and aperture (AP) retrieved flux fractions, gaussian-fitted source sizes, and the background RMS of the maps obtained, per calibrator and array, from observations (43 valid calib_1scan and beam maps) of the current run (N2R67). As indicated above, more accurate flux fractions will be obtained after analysis leading to new DAF sets based on these data and those that could be gathered after the start of the next NIKA2 science pool.