M82 Chandra → SQUDE Mock Spectrum Tutorial

The three figures are deliberately separated. Figure 1 contains only Chandra data, the Chandra-RMF-folded total model, and its response-folded model components; Figure 2 contains only SQUDE mock data and its SQUDE-RMF model; Figure 3 is the only common-axis comparison of SQUDE mock data, SQUDE model, and Chandra-RMF model. No empirical polynomial or image-level scaling is used.

Figure 1 · Chandra4′×4′ ACIS PHA, 50 counts/bin, 458 displayed bins; total and every model component are folded through the Chandra response.

Figure 2 · SQUDE mock50 ks seeded fake_pha from the same Chandra best-fit source model through the SQUDE ARF/RMF.

Figure 3 · RMF controlThe source and SQUDE ARF are fixed; only redistribution is replaced by the Chandra RMF.

1. Chandra ACIS data + total model + model components

This is the original combined 4′×4′ Chandra ACIS spectrum: it contains no SQUDE mock data or SQUDE response. Black points are Chandra data; orange is the total model forward-folded through the Chandra RMF and rate-conservingly rebinned onto the same 458 data bins. Dashed/dotted curves are the five model components; each is independently folded through the same Chandra response and rebinned to the data bins, rather than plotted as an unconvolved source spectrum.

tbabs_Gal × [tbabs_wind × (vapec_cool + vapec_hot + 2 Gaussian line proxies) + tbabs_PL × powerlaw]

CX semantics: the fixed 0.777/1.234-keV Gaussians are phenomenological soft-line diagnostics/proxies for this response tutorial. They are not a complete multi-line physical charge-exchange model like Zhang et al. (2014), and do not support an independent CX abundance or CX flux-fraction inference.

Chandra ACIS data, Chandra-RMF-folded total model and model components — Figure 1. Chandra only: 458 group=50 data bins; black data, orange total model, cool/hot VAPEC, two CX line proxies, and absorbed power law. Every model curve is folded through the Chandra response.

Download 1-column PNG Download 2-column PNG

Scientific scope: the current CIAO 4.18 source-only baseline gives χ²_Gehrels/dof = 1125.65/444 = 2.535. It is a reproducible response-propagation input, not a final publication-grade M82 physical fit; the component curves only expose model decomposition and do not improve or hide this limitation.

2. SQUDE mock data + SQUDE model

The fitted source from Figure 1 is passed through SQUDE ARF v1.1.1 and RMF v1.1.2 using a 50 ks fake_pha. The Sherpa UI-session Poisson RNG is fixed by set_rng(numpy.random.default_rng(20260719)); this reproducible realization has 58,298 raw counts. The original uses group_counts(50); the new min30 version reuses the identical raw PHA and changes only the display layer to group_counts(30). Both are linear–linear.

set_rng(numpy.random.default_rng(20260719))
set_source(2, chandra_bestfit_model)
fake_pha(2, arf="SQUDE_rsp_v1.1.1.arf", rmf="SQUDE_rsp_v1.1.2.rmf",
         exposure=50000.0, grouped=False, method=poisson_noise)

SQUDE mock data and SQUDE model — Figure 2. SQUDE only: black is the new mock data and orange is the same source model folded through the SQUDE RMF.

min50 1-column min50 2-column min30 1-column min30 2-column

3. SQUDE mock + SQUDE model + Chandra-RMF model

This is the full-aperture three-object comparison; each regional section below now has a separate analogue. Black points remain the Figure-2 SQUDE mock data; orange remains the SQUDE-RMF model; black dash-dot is the same best-fit source redistributed through the Chandra RMF. Both models retain the same SQUDE ARF, so the difference is RMF redistribution only.

r^control_i = Σ_j R^Chandra_ij F_j A^SQUDE_j; then overlap-rebin conservingly to the SQUDE data grid.

Full-aperture min50 RMF control — Figure 3 grouping-sensitivity slider. Both sides use the same raw PHA, source, responses, seed, and control operator; only display grouping changes. The slider pair has identical x/y limits. The Chandra-RMF control is not a Chandra-data spectrum.

Figure 3 grouping-sensitivity slider. Both sides use the same raw PHA, source, responses, seed, and control operator; only display grouping changes. The slider pair has identical x/y limits. The Chandra-RMF control is not a Chandra-data spectrum.

min50 1-column min50 2-column min30 1-column min30 2-column Download grouping-independent native model-grid CSV

4. Connected spectrum: SQUDE mock versus CCD resolution

This is an additional presentation and does not replace Figures 1–3 or the grouping sliders above. The blue curve directly joins the 971 display-bin centers of the same seeded 50 ks min30 SQUDE Poisson mock; it is a data realization, not a model, and has no error bars. The red curve is the deterministic control for the same source and fixed SQUDE ARF with Chandra ACIS RMF redistribution, evaluated on exactly the same energy grid. The expected response models differ only in RMF; the displayed blue realization also contains Poisson noise, grouping, and unequal-bin rate-density effects. The red curve is not a Chandra-data spectrum, and this figure is not evidence for fit quality, physical parameters, or individual line identifications.

M82 full aperture: connected blue SQUDE min30 Poisson mock data compared with the broad red Chandra ACIS RMF resolution control — Figure 4. The sharp connected blue spectrum is the SQUDE mock realization; the broad red curve is the Chandra-ACIS-RMF control at fixed SQUDE ARF. Select the image for the full-size two-column PNG.

Connected contrast 1-column Connected contrast 2-column Download V5 manifest Download V5 producer

4L. Connected spectrum labeled V2: 25 AtomDB/SQUDE keV reference guides

This is the annotation-only companion V2 to Figure 4 and does not replace Figure 4 or any figure, slider, or download above; the V1 labeled version (eight wavelength text labels placed over the data panel) remains in the bundle but is intentionally superseded. The blue Poisson connected line and the red Chandra-ACIS-RMF control curve are byte-for-byte identical to Figure 4 (same V5 plotted subset). V2 places 25 AtomDB/SQUDE keV-only grouped reference guides in a separate top annotation band above the data panel — all label text uses keV to match the x axis, and these are not independent detections or unique deblended fit assignments. The 25 guides are drawn from AtomDB 3.1.3 cross-matched to SQUDE project markers (representative dominant transitions, not a complete emissivity table), with bounded evidence provided by ../data/m82_line_label_v2_atomdb_evidence.json. The blue curve still includes Poisson noise, grouping, and unequal-bin rate-density effects; the red curve remains a deterministic response control, not a Chandra-data spectrum. This figure is not evidence for fit quality, physical parameters, or individual line identifications.

M82 full aperture labeled V2: connected blue SQUDE min30 Poisson mock data compared with the broad red Chandra ACIS RMF resolution control, with 25 AtomDB/SQUDE keV reference guides in a separate top annotation band — Figure 4L V2. The sharp connected blue spectrum is the SQUDE mock realization; the broad red curve is the Chandra-ACIS-RMF control at fixed SQUDE ARF. The 25 grey dotted lines and italic text labels in the separate top annotation band are AtomDB/SQUDE keV-only grouped reference guides (O VII triplet 0.568 keV, O VIII Lyα 0.654 keV, Fe XVIII 0.704 keV, Fe XVII blend 0.727 keV, etc.), **not detections or unique deblended fit assignments**. Select the image for the full-size two-column PNG.

V2 labeled 1-column V2 labeled 2-column Download V2 labeled manifest Download V2 labeled producer Download shared AtomDB bounded-evidence JSON

4R. Regional labeled V2: Center and North native-grid three-line comparison

This is the labeled three-line comparison V2 of the Center and North regions, and does not replace any figure, slider, or download above; the V1 regional labeled version (eight wavelength text labels placed over the data panel) remains in the bundle but is intentionally superseded. The blue (royalblue) curve is the 50 ks seeded min30 Poisson connected mock data for Center (40″×80″) on its native grouped display grid (464 display bins); the black curve is an independently seeded 50 ks min30 Poisson connected mock data for North (80″×80″) on its distinct native grouped display grid (101 display bins). Both curves are data realizations, not models, and have no error bars or interpolation. The red curve is a Center-only eight-epoch Chandra-RMF control: each epoch source is first folded through its own Chandra RMF at fixed SQUDE ARF, then exposure-weighted, and finally conservatively projected to the Center min30 display grid; it is not a Chandra-data spectrum and contains no area, peak, or integral renormalization. Center and North have different apertures, so curve heights are not same-area surface brightness. V2 places 25 AtomDB/SQUDE keV-only grouped reference guides in a separate top annotation band above the data panel — all label text uses keV to match the x axis, and these are not independent detections or unique deblended fit assignments. This figure is not evidence for fit quality, physical parameters, or individual line identifications.

M82 regional labeled V2: Center blue and North black 50 ks min30 Poisson connected mock data on native grids, overlaid with Center-only red eight-epoch Chandra-RMF control and 25 AtomDB/SQUDE keV reference guides in a separate top annotation band — Figure 4R V2. Blue is the SQUDE mock realization on the Center native min30 grid; black is the independent SQUDE mock realization on the distinct North native min30 grid; red is the Center-only eight-epoch fold-before-weight Chandra-RMF control at fixed SQUDE ARF. The 25 grey dotted lines and italic text labels in the separate top annotation band are AtomDB/SQUDE keV-only grouped reference guides, **not detections or unique deblended fit assignments**. Apertures differ; heights are not same-area surface brightness. Select the image for the full-size two-column PNG.

V2 regional labeled 1-column V2 regional labeled 2-column Download V2 regional labeled manifest Download V2 regional labeled producer Download shared AtomDB bounded-evidence JSON

4G. Grouping-sensitivity slider: Center/North min30 versus min20 interactive comparison

This is the grouping-sensitivity interactive slider for the Center and North regions, and does not replace any figure or download above. Both sides use the identical seeded PHAs (Center seed 2026071902, North seed 2026071901), the same 25 AtomDB/SQUDE keV-only grouped reference guides, colors and legend roles, energy range, and y-axis semantics. The left side shows min20 (group_counts 20): Center 653 display bins, North 145 display bins; the right side shows min30 (group_counts 30): Center 464 display bins, North 101 display bins. The red curve is the Center-only eight-epoch fold-before-weight Chandra-RMF control at fixed SQUDE ARF; both sides use the same Center source and epoch-specific RMFs, conservatively rebinned to the distinct min20/min30 display grids. Grouping changes the display layer only; each variant retains its native grid and absolute counts s⁻¹ keV⁻¹, with no interpolation, smoothing, or renormalization. Center and North have different apertures, so heights are not same-area surface brightness. This figure is not evidence for fit quality, physical parameters, or individual line identifications.

Center/North min30 three-line labeled — Figure 4G grouping-sensitivity slider. Both sides use the same seeded PHAs, the same 25 labels/colors/roles, and the eight-epoch fold-before-weight Center control; left is min20 (Center 653/North 145), right is min30 (Center 464/North 101). Grouping changes the display only; each variant retains its native grid and absolute counts s⁻¹ keV⁻¹; no interpolation/smoothing/renormalization; not same-area surface brightness.

Figure 4G grouping-sensitivity slider. Both sides use the same seeded PHAs, the same 25 labels/colors/roles, and the eight-epoch fold-before-weight Center control; left is min20 (Center 653/North 145), right is min30 (Center 464/North 101). Grouping changes the display only; each variant retains its native grid and absolute counts s⁻¹ keV⁻¹; no interpolation/smoothing/renormalization; not same-area surface brightness.

min20 1-column min20 2-column min30 1-column min30 2-column Download slider manifest Download slider producer

4H. Style-variant interactive comparison: Center min30 + North min10 three-way styleA/B/C switcher

This is the three-way style-variant interactive comparison for the Center min30 + North min10 seeded PHAs, and does not replace any figure, slider, or download above. All three style variants use the identical seeded PHAs (Center seed 2026071902 min30, North seed 2026071901 min10), the same energy range, grouping, and y-axis semantics. Style A = plain lines only (blue Center, black North, red Chandra-RMF control); Style B = Style A plus a white Chandra white halo behind the red control curve; Style C = Style B plus a white halo behind the North curve as well. Grouping is unchanged across all three variants; each retains its native grid and absolute counts s⁻¹ keV⁻¹, with no interpolation, smoothing, or renormalization. Center and North have different apertures, so heights are not same-area surface brightness. This figure is not evidence for fit quality, physical parameters, or individual line identifications.

Style A · plain linesStyle B · +Chandra white haloStyle C · +North white halo

Center min30 + North min10 style A: plain lines

Center min30 + North min10 style B: Chandra white halo

Center min30 + North min10 style C: Chandra + North white halo

Select a radio button to switch between the three style variants; the 2-column version is shown. Downloads for each style are below.

Style A: 1-column 2-column Style B: 1-column 2-column Style C: 1-column 2-column

Style A · plain lines Style A

Style B · Chandra white halo Style B

Style C · Chandra + North white halo Style C

Three-region extension: North / Center / South

Each region uses its own Chandra PHA/ARF/RMF and has three scientifically separate figures. Figure A is real Chandra data plus response-folded total/components. Figure B is an independently seeded 50 ks SQUDE fake_pha plus its SQUDE-folded model. Figure C mirrors the full-aperture Figure 3: the same SQUDE mock, the SQUDE-RMF model, and a Chandra-RMF redistribution control at fixed SQUDE ARF. Figure C is not a Chandra-data spectrum. North/South retain the five original model components; Center uses the eight-epoch joint diffuse/CX-line-proxy/Fe-K plus epoch-variable XRB/ULX model. Every SQUDE panel retains the original min50 asset and adds a min30 version that changes display grouping only.

Region	Chandra bins	baseline rstat	0.3–4 keV thermal fraction	SQUDE raw counts / seed
North wind 80″×80″	176	1.096	95.8%	3,636 / 2026071901
Center starburst 40″×80″	459	1.200 joint	58.5%	27,040 / 2026071902
South wind 80″×80″	154	1.199	87.8%	4,916 / 2026071903

Center method and scope: the eight center epochs differ in count rate by a factor of 2.40, invalidating the merged-spectrum static fit (rstat=8.61). The replacement jointly fits all eight PHAs: diffuse VAPEC/CX-line-proxy/Fe-K parameters are shared, while each ObsID has an independent absorbed XRB/ULX normalization and effective absorption; the XRB slope is tied. The result is χ²_Gehrels/dof=2576.83/2147=1.200, Q=3.27×10⁻¹⁰, kT=0.709 keV, Γ_XRB=1.18, and an exposure-weighted 0.3–4 keV thermal fraction of 58.5%. The low Q means the formal null is still rejected: this is a substantially improved tutorial forward model, not a final physical fit. Broad-aperture point-source pile-up is not modeled separately and the legacy PHAs have no BACKFILE; a point-source-excised re-extraction remains preferred for diffuse-only inference.

Numerical validation and reproduction

Check	Result
Explicit Chandra RMF operator vs Sherpa native fold	p95 relative error = 2.45×10⁻¹⁵
Chandra total vs sum of Chandra-response-folded model components	p95 relative error = 2.83×10⁻¹⁵
SQUDE total vs sum of model components	p95 relative error = 5.92×10⁻¹⁶
Three-region Chandra component closure	p95 ≤ 3.42×10⁻¹⁵ in every region
Regional/eight-epoch explicit RMF operator vs Sherpa	p95 ≤ 2.79×10⁻¹⁵
Three-region SQUDE component closure	p95 ≤ 6.28×10⁻¹⁶ in every region
min50 → min30 displayed bins (0.5–1.7 keV)	Full 662→971; North 61→101; Center 297→464; South 83→139; unchanged raw PHA
Three-region Chandra-RMF control rate-conserving rebin	relative rate error ≤ 1.90×10⁻¹⁶

cd ~/program/M82
export ASCDS_OVERRIDE=1
source ~/software/ciao-4.18/bin/ciao.sh -q
export PFILES="$PWD/pfiles;$ASCDS_INSTALL/param:"
python scripts/make_m82_mock_tutorial_figure_set.py
python scripts/make_m82_three_region_joint_center_tutorial_figures.py

Download complete executable script · Download full-aperture grouping provenance manifest

SQUDE M82