Research Articles (Physics)

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Browsing by Subject "Absorption lines"

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    The COS-Halos survey: Rationale, design and a census of circumgalactic neutral hydrogen
    (IOP Publishing, 2013) Tumlinson, Jason; Thom, Christopher; Dave, Romeel; Werk, Jessica K.; Prochaska, J. Xavier; Tripp, Todd M.; Katz, Neal; Oppenheimer, Benjamin D.; Meiring, Joseph D.; Ford, Amanda Brady; O'Meara, John M.; Peeples, Molly S.; Sembach, Kenneth R.; Weinberg, David H.
    We present the design and methods of the COS-Halos survey, a systematic investigation of the gaseous halos of 44 z = 0.15–0.35 galaxies using background QSOs observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. This survey has yielded 39 spectra of zem 0.5 QSOs with S/N ∼10–15 per resolution element. The QSO sightlines pass within 150 physical kpc of the galaxies, which span early and late types over stellar mass logM∗/M = 9.5–11.5. We find that the circumgalactic medium exhibits strong Hi, averaging 1Å in Lyα equivalent width out to 150 kpc, with 100% covering fraction for star-forming galaxies and 75% covering for passive galaxies. We find good agreement in column densities between this survey and previous studies over similar range of impact parameter. There is weak evidence for a difference between early- and late-type galaxies in the strength and distribution of Hi. Kinematics indicate that the detected material is bound to the host galaxy, such that 90% of the detected column density is confined within ±200 km s−1 of the galaxies. This material generally exists well below the halo virial temperatures at T 105 K. We evaluate a number of possible origin scenarios for the detected material, and in the end favor a simple model in which the bulk of the detected Hi arises in a bound, cool, low-density photoionized diffuse medium that is generic to all L ∗ galaxies and may harbor a total gaseous mass comparable to galactic stellar masses.
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    SIMBA: the average properties of the circumgalactic medium of 2 ≤ z ≤ 3 quasars are determined primarily by stellar feedback
    (Oxford University Press, 2020-10-05) Dave´, Romeel; Sorini, Daniele; Angles-Alc ´ azar, Daniel
    We use the SIMBA cosmological hydrodynamic simulation suite to explore the impact of feedback on the circumgalactic medium (CGM) and intergalactic medium (IGM) around 2 ≤ z ≤ 3 quasars. We identify quasars in SIMBA as the most rapidly accreting black holes, and show that they are well matched in bolometric luminosity and correlation strength to real quasars. We extract Lyα absorption in spectra passing at different transverse distances (10 kpc b 10 Mpc) around those quasars, and compare to observations of the mean Lyα absorption profile. The observations are well reproduced, except within 100 kpc from the foreground quasar, where SIMBA overproduces absorption; this could potentially be mitigated by including ionization from the quasar itself. By comparing runs with different feedback modules activated, we find that (mechanical) AGN feedback has little impact on the surrounding CGM even around these most highly luminous black holes, while stellar feedback has a significant impact. By further investigating thermodynamic and kinematic properties of CGM gas, we find that stellar feedback, and not AGN feedback, is the primary physical driver in determining the average properties of the CGM around z ∼ 2–3 quasars. We also compare our results with previous works, and find that SIMBA predicts much more absorption within 100 kpc than the NYX and ILLUSTRIS simulations, showing that the Lyα absorption profile can be a powerful constraint on simulations. Instruments such as VLT-MUSE and upcoming surveys (e.g. WEAVE and DESI) promise to further improve such constraints.