NGC 1275 December 2022

General information

Name of the source: NGC 1275, Perseus A, 3C 84
Brief description of the source:
- Seyfert 2 Galaxy
- z = 0.0175
- RA: 3 19 48.16 (hh mm ss), Dec: +41 30 42.1088 (dd mm ss)
- RA, Dec in deg (ICRS): 49.95066663, 41.5116969

Analysis by Chaitanya Priyadarshi ((IFAE - cpriyadarshi@ifae.es)

Data-taking information

Dates of data-taking: 20221220, 20221221

- 20221220 (1.34 h)
  - ZD range (deg): [34.61, 51.48]
  - AZ range (deg): [-59.00, 56.85]
  - Runs: 11522, 11528 - 11531
  - Joint observations with MAGIC? : No

- 20221221 (0.83 h)
  - ZD range (deg): [12.56, 14.08]
  - AZ range (deg): [-21.29, 23.77]
  - Runs: 11546 - 11550
  - Joint observations with MAGIC? : Not for the last 2 runs and there is some discontinuity in observation time

- 20221222 (1.46 h)
  - ZD range (deg): [12.68, 17.02]
  - AZ range (deg): [-36.55, 37.48]
  - Runs: 11566, 11568 - 11574
  - Joint observations with MAGIC? : Yes

Monte Carlo information

For getting a closer data-MC comparison, we produce MC data along various sky positions (nodes) as a preliminary method to facilitate a better Random Forest model for the reconstruction and to interpolate IRFs from various sky positions to the target position of each Observation Run.

DL1 data

This includes whether you use LSTOSA, specific versions of lstchain, dllab scripts, cleaning levels, and calibration information.

DL1a files produced by LSTOSA (lstchain v0.9)

original real DL1a data

/fefs/aswg/data/real/DL1/{Date}/v0.9/tailcut84/

lstchain v0.9 tailcut8-4 (with cleaning based on pedestal RMS, dynamical cleaning)

 /fefs/aswg/data/real/DL1/20221220/v0.9/tailcut84/log/lstchain_config_v0.9.4_from2022onwards_heuristic.json

MC nodes: tailcut8-4 (with cleaning based on pedestal RMS), dynamic cleaning, NSB tuning

 /fefs/aswg/data/mc/DL1/AllSky/20221104_src3_dec3476_4822_tuned/{Testing, Training}Dataset/

Random forest

Here we use the TrainingDataset nodes, selected along the declination path (or closer to) of the selected source (BL Lac here). The "dec3476" part in the production ID refers to the declination angle of +34.76 deg and similarly for "4822". We have combined the Training nodes of the 2 declination lines to have a better RF model for the declination path of the source NGC 1275. See All_sky_mc_bllac for more information.

In this new RF model production, we include zenith and azimuth pointing parameters as well.

lstchain v0.9.13dev source-independent, dynamic cleaning, NSB tuning on BL Lac,

 /fefs/aswg/workspace/seiya.nozaki/BLLac_paper/20221104_src3_dec3476_4822_tuned/merged/srcindep/RF/trained_models/

For IRF interpolation

Here we create an almost uniform grid of nodes of sky positions for TestingDataset MC, so as to facilitate IRF interpolation in the parameter space of cos zenith and the sin of angle (delta) between the geomagnetic field and the particle shower direction. IRF interpolation is performed using pyirf v0.7.

Link to MC DL2 files used:

/fefs/aswg/workspace/seiya.nozaki/BLLac_paper/20221104_src3_dec3476_4822_tuned/merged/srcindep/DL2_MC/data/

Particle types: ring-wobble gamma (offset range = [0.3999, 0.4001] deg)

DL2 data

The DL2 files of the real data are stored here - /fefs/aswg/workspace/chaitanya.priyadarshi/real_data/AGN/NGC1275/v09x/tailcut84/DL2/real/src_indep/20221104_dec3476_4822_tuned/{Date}

DL3 data selection

For energy-dependent cuts

Information about your DL3 data selection.

intensity > 50
r: [0, 1]
wl: [0.01, 1]
leakage_intensity_width_2: [0, 1]

source-independent
- gh_efficiency: 0.8
- theta_containment: 0.8

Energy-dependent Gammaness and Theta cut distribution

High-level analysis

lstchain Tools to generate source-independent IRF and DL3
Science Tool: gammapy 1.0
point-like IRF, 1D analysis

For DL3 data reduction to DL4 dataset,

OFF regions selected - 2 Wobble
Excluded region: IC 310, circular region with radius 0.3 deg
Safe Energy mask for systematics - Yes, 39.8 GeV < E < 40 TeV
Energy axes -
- True: 10 GeV to 100 TeV with 10 bins per decade
- Reco: 10 GeV to 100 TeV with 10 bins per decade

For spectral analysis,

Model used - Exponential Cutoff Power Law (5.58 sigmas preference over Power Law for the full dataset) + EBL (Dominguez), Log Parabola (For 20221220) + EBL (Dominguez)
Reference energy used by calculating the decorrelation energy with a Power Law fit, 295 GeV
Spectral Fit energy range - 39.8 GeV to 100 TeV with 10 bins per decade
Spectral fit with gammapy default optimization - minuit

For LC,