Assigned ID: 40 ----- Attempting Submission 1 (Sun Feb 21 03:20:50 GMT 2010) ----- ----- Attempting Submission 1 (Fri Jul 09 20:18:45 GMT 2010) ----- Three Dimensional Mapping of the Magellanic Bridge by High-Resolution Spectroscopy toward Multiple Sightlines The Magellanic Bridge (the MB) is a physical connection between the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The MB contains a young stellar population that was probably formed in local molecular clouds, while it is still not fully settled whether the larger Magellanic Stream, produced by the LMC/SMC unit sweeping through the Milky Way halo, contains only gas or has any stellar populations. We propose HST/COS spectroscopy of four sight-lines of the MB toward QSOs/AGNs behind it, covering various absorption lines such as O I, Fe II, Si II, C II, Si IV, and C IV. This will be combined with one existing STIS observation of B0312-770 which we have already modeled in detail, and with our recent high resolution VLT/UVES observations of all five sight-lines, covering Ca II H,K and Na I D_1, D_2. The five sight-lines cover a range of H I column densities from 10^19 (cm^-2) up to above the damped Lya (DLA) threshold. Effectively, the proposed COS observations of multiple sightlines through the MB will provide a map of the surroundings of a DLA absorber, allowing us to study how it connects with other classes of absorbers, and with the surrounding structures. Our goals are to (1) evaluate physical conditions of gas clouds in the MB along multiple sight-lines derived from the photoionization models, (2) search for correlations between the physical conditions of the MB gas, the H I 21cm radio emission density, and the distance from the SMC, and (3) compare the physical conditions of the MB to those of high-z absorption systems like DLA systems because the MB, with its low metallicity and possible dust deficiency, could be a local analog.
Our goal is to observe 3 QSOs/AGNs with suffiently high S/N ratios (S/N ~ 10 per resolution element) in order to detect various UV absorption lines arising in the Magellanic Bridge absorbers, and fit Voigt profile models to them. For all the lines of sight we will use the G130M grating with lambda_c =1291˚A to cover 1132–1433˚A, and the G160M grating with lambda_c =1600˚A to cover 1405–1775˚A. The former covers Si II λλ1190,1193, N I λ1200, Si III λ1207, Lyα, N V λλ1239,1243, S II λ1254, Si II λ1260, O I λ1302, Si II λ1304, N II λ1317, C I λ1329, C II λ1335, and Si IV λ1394,1403, while the latter covers Si II λ1527, C IV λ1548,1551, Fe II λ1608, Al II λ1671. All of these were detected in the sightline toward B 0312 −770. The spectral resolution of G130M and G160M (R ∼ 20,000 – 24,000, FWHM ∼ 12.5 – 15 km/s) is high enough to resolve absorption profiles into multiple narrower components. As the TAC suggested, the flux of one the originally proposed lines of sight might have been overestimated, thus we selected the three best targets and redistributed 2 orbits to increase the S/N of the selected targets. As a result, we also include the setups G130M grating with lambda_c =1327 A and G160M grating with lambda_c =1577 A for HB89-0202-765. For the four setups of this line of sight, and the two setups of UKS-0242-724 and ESO031-G08, we will use the four-step 3 and 4 COS FP-SPLIT mode to reduce fixed pattern noise and avoid having important lines fall on grid wires. We used the ETC on the HST/COS web-site to calculate the necessary exposure times to obtain spectra with, at least, S/N = 10 per resolution element. The only direct information we have about UV flux of our targets are from the GALEX archive. However, most of our targets are located at the edge of observed frames and their GALEX fluxes might not be reliable. Instead, we estimated the UV fluxes of our targets by extrapolating from their optical fluxes. This procedure is acceptable because our targets are all at low redshift (z< 0.4) and Lyman limit (LL) systems, if present, would not affect our observed wavelength range (lambda > 1132A) unless zLL > 0.24. We used alpha = -1 as power-law index of quasar spectra, with which we never over-estimate the UV fluxes because the typical power-law index is alpha = -1.56. These fluxes are included as "Other Fluxes" later in the proposal. QUASAR ABSORPTION LINES AND IGM 12 false 0.0 0.0 false false false false false false SUPPORTED GALAXY QSO This object was generated by the targetselector and retrieved from the NED database. 0.3E-14 ergs/s/cm2/A J2000 02 02 13.7000 -76 20 3.00 J2000 GALAXY QSO SEYFERT This object was generated by the targetselector and retrieved from the NED database. 0.9E-14 ergs/s/cm2/A J2000 02 43 9.6000 -72 16 48.00 J2000 GALAXY QSO SEYFERT This object was generated by the targetselector and retrieved from the NED database. 1.3E-14 ergs/s/cm2/A J2000 03 07 35.3000 -72 50 3.00 J2000 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G160M 1600 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G160M 1600 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G160M 1600 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G160M 1600 /Users/paola/Documents/OP-cache/PhaseII_MB_HST_Proposal-v01.xml The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12263 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 14:58:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 626256 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12263 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12263 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3300 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3633 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12263 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3411 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3633 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12263 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3411 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3633 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12263 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3411 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3633 :pcs-gap 0 ) true 4 0 Acquisition exposure with G130M spectral element Calculated for 0.5*F(1700)=0.23E-14 erg/cm2/s/A COS ETC result for S/N=50 is 17 sec (id COS.A330397). Count rate 484 /sec. 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec /Users/paola/Documents/OP-cache/PhaseII_MB_HST_Proposal-v02.xml The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12263 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 14:58:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 313168 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12263 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12263 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3312 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3645 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12263 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3423 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3645 :pcs-gap 0 ) true 2 0 Acquisition exposure with G130M spectral element Calculated for 0.5*F(1700)=0.23E-14 erg/cm2/s/A COS ETC result for S/N=50 is 17 sec (id COS.A330397). Count rate 484 /sec. 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec 2/3rds of buffer time at twice nominal flux is 1589 sec The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. /Users/paola/Documents/OP-cache/PhaseII_MB_HST_Proposal-v03.xml (Tic-Visit :proposal-id 12263 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 14:58:07.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 313168 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12263 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12263 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3312 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3645 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12263 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3423 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3645 :pcs-gap 0 ) true 2 0 Acquisition exposure with G130M spectral element Calculated for 0.5*F(1700)=0.33E-14 erg/cm2/s/A COS ETC result for S/N=50 is 12 sec (id COS.A330401). Count rate 559 /sec. 2/3rds of buffer time at twice nominal flux is 1220 sec 2/3rds of buffer time at twice nominal flux is 1220 sec 2/3rds of buffer time at twice nominal flux is 1220 sec 2/3rds of buffer time at twice nominal flux is 1220 sec