🔭 DRAFT RESEARCH PROPOSAL · INFRARED IMAGING · JWST NIRCam + MIRI
Improving current electromagnetic accretion constraints by 1–2 orders of magnitude through deep multi-band infrared photometry targeting ultra-low-luminosity accretion onto the candidate IMBH — complementary to the NIRSpec/IFU managed environment proposal · Working draft · April 2026
Existing multi-wavelength limits on accretion in OC's core:
For a 20,000–50,000 M☉ IMBH, these constraints imply accretion at extraordinarily sub-Eddington rates. However, the existing Chen et al. observations were not optimised for maximum depth or confusion mitigation. Improving IR limits by 1–2 orders of magnitude would constrain Ṁ below 10⁻¹¹–10⁻¹² Ṁ_Edd — definitively establishing OC as either the most weakly accreting known black hole or revealing a faint counterpart below current sensitivity.
For an IMBH of 20,000–50,000 M☉:
This is accessible to deep JWST integrations with careful crowded-field treatment.
| Parameter | Value |
|---|---|
| Filters | F200W, F356W, F444W (red continuum + non-stellar SED signature) |
| Exposure per filter | 20 ks (~5.5 hr); 3 filters = 60 ks (~17 hr) |
| Achieved sensitivity | ~5–10 nJy (confusion-limited; 3× crowding penalty applied) |
| Crowding mitigation | PSF subtraction using WebbPSF; sub-pixel dithering; empirical PSF from off-centre fields |
| Target luminosity | L ≈ few × 10³⁰ erg/s at SNR = 5 |
| Parameter | Value |
|---|---|
| Filters | F770W, F1000W (mid-IR excess from dusty inflow or reprocessed emission) |
| Exposure per filter | 15 ks (~4 hr each); 2 filters = 30 ks (~8 hr) |
| Achieved sensitivity | ~30–70 nJy |
| Science targets | Dusty inflow; reprocessed accretion emission; non-stellar IR excess |
Two epochs separated by ~6 months provide variability detection at ≥20–30% amplitude, enabling rejection of stellar contaminants (which do not vary at this level on this timescale) and detection of accretion flares. A variable non-stellar point source at OC's dynamical centre would be a compelling IMBH counterpart candidate.
| Component | Time |
|---|---|
| NIRCam (3 filters × 20 ks × 2 epochs) | ~34 hr |
| MIRI (2 filters × 15 ks × 2 epochs) | ~16 hr |
| Overheads (~30%) | ~15 hr |
| Total JWST request | ~65 hr (two-epoch program) |
The ELT (first light 2028) will provide ~5–10 mas angular resolution in AO mode — directly resolving the confusion-limited core at OC's distance. An ELT AO imaging program (5–10 hr, sensitivity comparable to JWST at higher angular resolution) would confirm or rule out any JWST candidate. This can be submitted as a companion ELT proposal once a JWST detection or strong upper limit is in hand.
| Scenario | Outcome | OCS Implication |
|---|---|---|
| Detection: L_IR ≳ few × 10³⁰ erg/s | First EM counterpart to OC IMBH; constrain Ṁ and radiative efficiency η | Natural quiescent accretion — consistent with null and OCS hypotheses alike |
| Non-detection: L < 10³⁰ erg/s | Upper limit: Ṁ < 10⁻¹²–10⁻¹¹ Ṁ_Edd; OC becomes benchmark for radiatively inefficient accretion | Deepest EM silence yet — strengthens both gas-starvation and managed-environment interpretations |
| Variable source detected | Accretion variability; strong IMBH counterpart candidate | Triggers multi-wavelength follow-up including KM3NeT/IceCube ToO |
| Year | Q | Milestone | Deliverable |
|---|---|---|---|
| 1 | Q1–Q2 | JWST GO proposal preparation; PSF modelling pipeline setup | JWST proposal submitted to Cycle 4/5 |
| 1–2 | — | JWST observations executed (TAC scheduling) | Raw NIRCam + MIRI data |
| 2 | Q1–Q2 | Crowded-field photometry; epoch-1 deep limits | First-epoch sensitivity curves |
| 2 | Q3–Q4 | Epoch-2 observations; variability analysis | Variability catalogue |
| 3 | Q1–Q2 | SED fitting; accretion modelling; radio cross-check | Draft paper (deep limits or detection) |
| 3 | Q3–Q4 | Publication; public data release | Submitted to ApJ |
| Item | Cost (USD) | Notes |
|---|---|---|
| PI (0.2 FTE, 3yr) | 225,000 | IR astronomy / JWST data expertise required |
| Postdoc (1.0 FTE, 3yr) | 285,000 | NIRCam + MIRI reduction; crowded-field photometry lead |
| Graduate student (1.0 FTE, 3yr) | 165,000 | SED modelling; accretion flow interpretation |
| Co-I support (2 × 0.1 FTE) | 240,000 | Stellar dynamics + high-energy interface |
| JWST time | 0 | Awarded via TAC (no direct cost) |
| HPC + cloud storage | 80,000 | NIRCam mosaics; MIRI data cubes |
| Travel + publications | 60,000 | STScI JWST meetings; 2 open-access papers |
| Fringe + overhead (~30%) | 255,000 | |
| Total | ~$1.31M (3 yr) |