Unsupported characters were found in Observing Description and replaced with |*|Phase II Submission 12071218872----- Attempting Submission 1 (Tue Aug 18 21:48:17 GMT 2026) -----Unsupported characters in observing description.Unveiling the Elusive Population of Local Nitrogen EmittersJWST spectroscopy of high-z galaxies has uncovered a population of starbursts with unusually dense, Nitrogen (N) rich gas via rest-UV nebular emission. These objects are likely key to understanding star-formation driving cosmic dawn galaxies, however their immense distances hinder acquisition of high SNR data and prohibit spatially resolved studies. A path forward is to leverage analogs in the local universe, but identifying analogs is challenging; optical spectra are typically insufficient to reveal dense, N-rich gas to inform requisite UV follow-up. As such, the sample of known-analogs remains at 1. We present a new indicator to select objects via anomalously strong [N II]5755 and high [N II]5755/6584, implying high densities ne>10^5 cm^-3 and supersolar N/O, as well as optical wolf-rayet wind features, implying modest metallicities and young stellar populations. Using four promising candidates (of ~10) selected by this approach from SDSS+DESI DR1, we propose a pilot study with COS to acquire FUV+NUV spectroscopic coverage of the UV nebular features necessary to both confirm the presence of high density, N-rich gas, and characterize the ISM. This proposal will 1) Probe the conditions of N-enrichment via C/O and N/O abundances of 4 promising local N-emitters, identfying whether the source of N is also C-rich (e.g., WR, AGB), and more broadly 2) will validate a new approach for identifying local N-emitters. The upcoming DESI release will ~4x this sample, enabling high SNR demographic studies of these objects in regimes which are simply impractical in their high-z counterparts (e.g., R >1000 Opitcal/UV, resolved IFU, X-ray, MIR, Radio).Observations Overview:
We divide the approved 17-orbit program into six independent, configuration-specific COS visits. Four targets will each be observed for three orbits with COS/NUV G230L at CENWAVE=2950. Target 39628309423723142 will additionally be observed for two orbits with G230L at CENWAVE=3360, and target 39633389581502446 will additionally be observed for three orbits with COS/FUV G140L at CENWAVE=1105. One grating and central-wavelength configuration is used per visit to maximize long-dwell science integrations and minimize configuration-change overheads.
Target Acquisition: Each visit begins with a COS/NUV ACQ/IMAGE exposure through the PSA. MIRRORA is used for J233846.84+181719.3 and 39628309423723142, while MIRRORB is used for the two brighter targets 39627959371301130 and 39633389581502446 to reduce their NUV imaging count rates. The acquisition exposure times are determined with the COS ETC to provide S/N of at least 25, with S/N=50 adopted where practical. The ETC source models are normalized conservatively to the compact source|*|s available UV and optical photometry. The final coordinates are registered to the compact UV/blue star-forming component responsible for the optical emission-line spectrum. No ACQ/SEARCH is requested because the final coordinate uncertainties are less than 0.4 arcsec. All acquisition and science exposures will be verified with the APT Bright Object Tool.
G230L Science Exposures:
The G230L observations use the PSA in TIME-TAG mode with automatic wavelength-calibration flashes. We employ a long-dwell strategy with one science exposure per orbit. FP-POS values are changed between orbits where permitted by wavelength coverage. For J233846.84+181719.3 we use FP-POS 2, 3, and 4; for 39628309423723142 at CENWAVE=2950 we use FP-POS 1, 3, and 4; at CENWAVE=3360 we use FP-POS 1 and 4; for 39627959371301130 we use FP-POS 1, 3, and 4; and for 39633389581502446 we use FP-POS 3, 4, and 4. These selections dither the spectra across the detector while retaining the blue O III] lines for the two lowest-redshift targets. The G230L/3360 first-order Stripe A spectrum provides Si III] and C III] for the highest-redshift target.
G140L Science Exposures: The G140L observations use the PSA in TIME-TAG mode at CENWAVE=1105, with SEGMENT=A and LIFETIME-POS=LP11. The four FP-POS settings are specified individually and executed in monotonically increasing order across the three-orbit visit. FP-POS 2 and 3 are divided between adjacent orbits so that the cumulative exposure time is approximately equal at all four FP-POS positions while avoiding inefficient backward grating movements. Automatic wavelength-calibration flashes are enabled. BUFFER-TIME values are calculated from the ETC after the final exposure durations and orbit packing have been established. The ETC yields and SNR per resel < 23 assuming continuum for a GALEX FUV mag 17.1 at 1486 Angstroms (expected location of low EW line) and SNR per resel < 10 at 1909 angstroms assuming C III] line EW of 1 Angstrom.6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYDWARF COMPACTSTAR FORMING REGIONNOJ2000umag=18.17, z=0.0165GALAXYDWARF COMPACTSTARBURSTNOJ2000z=0.1344GALAXYDWARF COMPACTSTARBURSTNOJ2000z=0.0299GALAXYDWARF COMPACTSTARBURSTNOJ2000z=0.0047The scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Three-orbit COS/NUV G230L/2950 visit. One long science exposure per orbit; FP-POS values 2, 3, and 4 preserve blue O III] coverage while dithering the spectrum.(Tic-Visit
:proposal-id 18354
:visit-id "01"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:45.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 3
:saa-model "32"
:si-bright-earth-limb-angle 20.0
:data-volume 469728
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "01"
:obset-id "01"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "01"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2587
:al-overhead-at-end 0
:internal-dur-at-end 95
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2976
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "01"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2592
:al-overhead-at-end 0
:internal-dur-at-end 114
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2976
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "01"
:orbit-number 3
:pcs-time 380
:si-vis-utilization 2592
:al-overhead-at-end 0
:internal-dur-at-end 423
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2976
:pcs-gap 0
)true30ETC set for TA SN 50.Buffer time set as 2/3 of buffer fill time estimated by ETC as 2100sBuffer time set as 2/3 of buffer fill time estimated by ETC as 2100sBuffer time set as 2/3 of buffer fill time estimated by ETC as 2100sThe scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Three-orbit COS/NUV G230L/2950 visit. One long science exposure per orbit; FP-POS values 1, 3, and 4 provide broad detector-position sampling.(Tic-Visit
:proposal-id 18354
:visit-id "02"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:45.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 3
:saa-model "32"
:si-bright-earth-limb-angle 20.0
:data-volume 469728
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "02"
:obset-id "02"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "02"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2599
:al-overhead-at-end 0
:internal-dur-at-end 95
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2979
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "02"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2597
:al-overhead-at-end 0
:internal-dur-at-end 114
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2979
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "02"
:orbit-number 3
:pcs-time 380
:si-vis-utilization 2597
:al-overhead-at-end 0
:internal-dur-at-end 423
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2979
:pcs-gap 0
)true30Exposure set for SN = 25 given GALEX FUV 20.6 magBuffer time set at 2/3 fill time from ETC (2000s)Buffer time set at 2/3 fill time from ETC (2000s)Buffer time set at 2/3 fill time from ETC (2000s)The scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Two-orbit COS/NUV G230L/3360 visit. FP-POS values 1 and 4 maximize detector separation while retaining first-order Stripe A coverage of Si III] and C III].(Tic-Visit
:proposal-id 18354
:visit-id "03"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:46.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "32"
:si-bright-earth-limb-angle 20.0
:data-volume 313184
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "03"
:obset-id "03"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "03"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2599
:al-overhead-at-end 0
:internal-dur-at-end 95
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2979
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "03"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2597
:al-overhead-at-end 0
:internal-dur-at-end 423
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2979
:pcs-gap 0
)true20Exposure set for SN = 25 given GALEX FUV 20.6 magBuffer time set at 2/3 fill time from ETC (2000s)Buffer time set at 2/3 fill time from ETC (2000s)The scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Three-orbit COS/NUV G230L/2950 visit. One long science exposure per orbit; FP-POS values 1, 3, and 4 provide broad detector-position sampling.(Tic-Visit
:proposal-id 18354
:visit-id "04"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:46.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 3
:saa-model "32"
:si-bright-earth-limb-angle 20.0
:data-volume 469728
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "04"
:obset-id "04"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "04"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2595
:al-overhead-at-end 0
:internal-dur-at-end 95
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2977
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "04"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2577
:al-overhead-at-end 0
:internal-dur-at-end 114
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2977
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "04"
:orbit-number 3
:pcs-time 380
:si-vis-utilization 2577
:al-overhead-at-end 0
:internal-dur-at-end 423
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2977
:pcs-gap 0
)true30Target ACQ/IMAGE exposure timeset for S/N 25 using Mirror B due to GALEX FUV = 17.3 magBuffer TIme set to 2/3 of Buffer Fill time which is 2000s on the ETCBuffer TIme set to 2/3 of Buffer Fill time which is 2000s on the ETCBuffer TIme set to 2/3 of Buffer Fill time which is 2000s on the ETCThe scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Three-orbit COS/NUV G230L/2950 visit. FP-POS values 3, 4, and 4 prioritize retention of the blue O III] component; the repeated FP-POS=4 exposure is deliberate.(Tic-Visit
:proposal-id 18354
:visit-id "05"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:46.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 3
:saa-model "32"
:si-bright-earth-limb-angle 20.0
:data-volume 487136
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "05"
:obset-id "05"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "05"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2671
:al-overhead-at-end 0
:internal-dur-at-end 95
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "05"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2677
:al-overhead-at-end 0
:internal-dur-at-end 124
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "05"
:orbit-number 3
:pcs-time 380
:si-vis-utilization 2677
:al-overhead-at-end 0
:internal-dur-at-end 433
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)true30Target ACQ/IMAGE requires MirrorB as GALEX FUV is 17 mag, set to recommended SN 50.Buffer time set as 2/3 of fill time from etc (2000s)Buffer time set as 2/3 of fill time from etc (2000s)Buffer time set as 2/3 of fill time from etc (2000s)The scheduling data was generated by CASM 34.2.CASM was run in Phase II mode.Three-orbit COS/FUV G140L/1105 visit. The four FP-POS settings are specified individually in increasing order. FP-POS 2 and 3 are split across adjacent orbits to balance cumulative exposure among all four positions while minimizing grating-motion overhead.(Tic-Visit
:proposal-id 18354
:visit-id "07"
:proposal-version -1
:trans-version "20260618"
:date "18-Aug-2026 14:44:47.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 3
:saa-model "31"
:si-bright-earth-limb-angle 20.0
:data-volume 156800
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18354
:visit-id "07"
:obset-id "07"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18354
:visit-id "07"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2682
:al-overhead-at-end 0
:internal-dur-at-end 38
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "07"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2678
:al-overhead-at-end 0
:internal-dur-at-end 48
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18354
:visit-id "07"
:orbit-number 3
:pcs-time 380
:si-vis-utilization 2679
:al-overhead-at-end 0
:internal-dur-at-end 376
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3064
:pcs-gap 0
)true30Target ACQ/IMAGE requires Mirror B as GALEX FUV is 17 mag, set to SNR=50Buffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setupBuffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setupBuffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setupBuffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setupBuffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setupBuffer time set as 2/3 of fill time from etc (8000s). ETC linked is combined exposure, ETC yields an SNR 23 per resel for the 4 FP-POS setup