joint Chandra/HST program approved by the Chandra TAC -561128847 Assigned ID: 6921 ----- Attempting Submission 1 (Fri Aug 29 19:23:28 GMT 2025) ----- HST Phase I Proposal 6921 successfully submitted. Receipt: # 6921-1 FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser full frame version with orientation constraints for visits 5-6 to avoid bright star contamination -149942443 ----- Attempting Submission 1 (Fri Oct 03 05:30:41 GMT 2025) ----- HST Phase II Proposal 18195 successfully submitted. Receipt: # 18195-1 ----- Attempting Submission 2 (Wed Oct 29 21:38:59 GMT 2025) ----- We used flash exposures as suggested by our STScI contact scientist X-ray properties of rapidly growing IMBHs from e-Rosita and high-resolution imaging of their host galaxies A population of intermediate black holes (IMBH) will allow us to solve one of the long-standing problems in modern astrophysics, the origin of supermassive black holes. We applied data mining to SDSS spectroscopic sample and identified 1928 type-I AGN candidates powered by `light' BHs (MBH<1e6). Then we used eROSITA-ERASS1 data release and identified 206 X-ray counterparts to these sources. 6 of them turned out to be rapidly growing black holes accreting at the rates 50-250% of the Eddington. We propose to observe them with Chandra to measure X-ray spectral slopes to relate them to normal SMBHs, and use HST WFC3 to get high-resolution images of their host galaxies to double the number of X-ray confirmed Eddington-limited IMBHs and get the first insight on structural properties their hosts. We propose to use the F300X, F350LP and F600LP filters. (i) the near-UV F300X is the deepest UV option in WFC3/UVIS; it will to isolate a compact active nucleus from star formation in the bulge (ii) the difference of F350LP and F600LP is much deeper than any blue optical WFC3 filter; it will allow reveal dust morphology in the inner part and will be crucial for the stellar population analysis of host galaxies combined with pure F600LP; (ii) F600LP will be the primary filter for the 2D light profile decomposition; (iii) F350LP and F600LP will provide the best stellar mass estimates for structural components. We computed stellar population models using pegase.2 for the proposed filter setup and confirmed its suitability. IC, IZ, and IK have been working together for over a decade; KG joined us in 2016 during his 1st undergraduate year and already co-authored several refereed papers (ApJ and ApJS; three of those papers were followed with press releases and attracted media attention), and gave numerous presentations at professional conferences including an invited talk (tutorial on the preparation of observations) at the 40th anniversary of the MMT observatory. VT is a PhD student at ESO-Garching and is an expert on eROSITA data. She performed the analysis of XMM-Newton, Chandra, and Swift X-ray data that led to the selection of targets for this proposal and also did search/identification of new intermediate-mass black hole candidates (paper in preparation). MD is a PhD student at MPIA working on IMBH characterisation for her PhD, she is in charge of the analysis of optical light curves for IMBH candidates based on ZTF and ATLAS transient surveys. FB is a professor at Universidad de Tarapaca (Chile). He is an expert in multi-wavelength studies of AGN and star-forming galaxies with Chandra, XMM-Newton, HST, ALMA, and a wide range of optical/near-IR ground-based facilities. EC is a graduate student supervised by FB. We have solid experience in the cutting-edge Virtual Observatory powered research in astrophysics which resulted in 2 publications in AAAS Science (Chilingarian et al. 2009 and Chilingarian and Zolotukhin 2015). With very limited manpower, we have successfully completed several projects, which included large-scale data analysis efforts, e.g. development of a dedicated data analysis technique and subsequent analysis of 1 million SDSS spectra. We compiled a multi-wavelength FUV-to-NIR Reference Catalog of Spectral Energy Distributions of galaxies (RCSED; Chilingarian et al. 2017 ApJS 228 14; http://rcsed.sai.msu.ru/) and identified the first bona fide population of intermediate-mass black holes using it (Chilingarian et al. 2018 ApJ 863 1). During the last 5 years we have been running a very successful multi-wavelength campaign on search and characterization of intermediate-mass black holes and their host galaxies using Chandra, XMM-Newton, Swift, intermediate-resolution ground-based optical spectroscopy using MagE at the 6.5-m Magellan Telescope, NIR ground-based imaging using Magellan and MMT. Our team has a 20-yr long expertise in reducing, analyzing, and publishing data from many IFU spectrographs operated on intermediate sized and large ground based telescopes (including but not limited to SAURON@WHT, PMAS@CalarAlto~3.5, GMOS-IFU@Gemini, VIMOS-IFU@VLT, FLAMES@VLT, NIFS@Gemini, SINFONI@VLT) including NIR spectrographs equipped with image slicers. We have performed analysis of multi-wavelength data for several projects in the past, including the IMBH search and identification project published in 2018 in ApJ which falls into the 2\% of most cited papers in astrophysics published in 2018. Supermassive Black Holes and Active Galaxies Galaxies 6 false true false false false false false true SECONDARY CHANDRA 27700256 false SUPPORTED GALAXY DWARF COMPACT QSO NO J2000 J2000 GALAXY DWARF COMPACT QSO NO J2000 J2000 GALAXY DWARF COMPACT QSO NO J2000 J2000 GALAXY DWARF COMPACT QSO NO J2000 J2000 GALAXY DWARF COMPACT QSO NO J2000 J2000 GALAXY DWARF COMPACT QSO NO J2000 J2000 WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP WFC3/UVIS Imaging No No F300X WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F600LP The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. 1767302730000 283.6955482137026 (Tic-Visit :proposal-id 18195 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:36:59.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. 1768657991000 283.0232835326012 (Tic-Visit :proposal-id 18195 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:37:00.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18195 :visit-id "03" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:37:01.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2599 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. 1768663585000 295.2258728140041 (Tic-Visit :proposal-id 18195 :visit-id "04" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:37:02.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2594 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18195 :visit-id "05" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:37:03.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "05" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2599 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18195 :visit-id "06" :proposal-version -1 :trans-version "20250624" :date "29-Oct-2025 17:37:04.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "06" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2594 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. /System/Volumes/Data/solaris/user1/wskipper/OP-cache/18195-v07.xml (Tic-Visit :proposal-id 18195 :visit-id "07" :proposal-version -1 :trans-version "20250929" :date "22-Jan-2026 14:33:34.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1732496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18195 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18195 :visit-id "07" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2594 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 1 0