2007A&A...465..171F


Query : 2007A&A...465..171F

2007A&A...465..171F - Astronomy and Astrophysics, volume 465, 171-184 (2007/4-1)

Hot halos around high redshift protogalaxies. Observations of OVI and NV absorption in damped Lyman-α systems.

FOX A.J., PETITJEAN P., LEDOUX C. and SRIANAND R.

Abstract (from CDS):

We present a study of the highly ionized gas (plasma) associated with damped Lyman-α (DLA) systems at z=2.1-3.1. We search for OVI absorption and corresponding SiIV, CIV, and NV in a Very Large Telescope/Ultraviolet-Visible Echelle Spectrograph (VLT/UVES) sample of 35 DLA systems with data covering OVI at S/N>10. We then use optical depth profile comparisons and ionization modelling to investigate the properties, phase structure, and origin of the plasma. We report twelve DLAs (nine intervening and three at <5000km/s from the QSO redshift) with detections of OVI absorption. There are no clear OVI non-detections, so the incidence of OVI in DLAs is between 34% (12/35) and 100%. Among these 12 DLAs, CIV and SiIV are seen whenever data is available, and NV is detected in 3 cases. Analysis of the line widths together with photoionization modelling suggests that two phases of DLA plasma exist: a hot, collisionally ionized phase (seen in broad OVI components), and a warm, photoionized phase (seen just in narrow CIV and SiIV components). The presence of inflows and/or outflows is indicated by individual OVI and CIV components displaced from the neutral gas (either blueshifted or redshifted) by up to 400km/s. We find tentative evidence (98% confidence) for correlations between the DLA metallicity (measured in the neutral gas) and high-ion column density, and between the DLA metallicity and high-ion line width, as would be expected if supernova-driven galactic outflows rather than accretion produced the high ions. Using conservative ionization corrections, we find lower limits to the total hydrogen column densities in the hot (OVI-bearing) and warm (CIV-bearing) phases in the range logNHIIHot>19.5 to >21.1, and logN_H II_Warm>19.4 to >20.9. On average, the hot and warm phases thus contain >40% and >20% of the baryonic mass of the neutral phase in DLAs, respectively. If the temperature in the OVI phase is ≃106K and so fOVI=OVI/O≪0.2, the plasma can make a significant contribution to the metal budget at high redshift. Additional searches for OVI in Lyman Limit Systems (QSO absorbers with 17.0<NHI<20.3) will be necessary to determine the total quantity of baryons and metals hidden in hot halos at z≃2.

Abstract Copyright:

Journal keyword(s): quasars: absorption lines - cosmology: observations - galaxies: high-redshift - galaxies: halos - galaxies: ISM

Nomenclature: Table 1: [FPL2007] QSO JHHMM+DDMM abs N.NNN N=12.

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 QSO B0027-1836 QSO 00 30 23.6259434280 -18 19 56.117225244   18.2 17.9     ~ 52 0
2 QSO B0112-30 QSO 01 15 04.8742901280 -30 25 14.952952308           ~ 49 1
3 QSO J0453-1305 QSO 04 53 13.5744238944 -13 05 55.085318988   13.2 16.5     ~ 92 2
4 NGC 1705 SBG 04 54 13.4661493464 -53 21 39.471592428 12.32 12.96 12.56 12.58 12.9 ~ 647 1
5 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16984 1
6 QSO B0528-2505 QSO 05 30 07.9627395840 -25 03 29.900044512   18.17 17.34 17.7   ~ 418 0
7 QSO B0841+129 BLL 08 44 24.2445546984 +12 45 46.526286780   18.28 18.5     ~ 118 0
8 QSO B0913+0715 QSO 09 16 13.9618240848 +07 02 24.497778588     17.1     ~ 105 0
9 QSO B1337+11 QSO 13 40 02.5419344664 +11 06 30.181521168     18.7     ~ 116 0
10 QSO B1409+0930 QSO 14 12 17.2929417480 +09 16 24.707943048     18.6     ~ 63 0
11 QSO B2059-360 QSO 21 02 44.6068720464 -35 53 07.081042308   19.18 18.62     ~ 57 0
12 LBQS 2138-4427 QSO 21 41 59.5007724552 -44 13 25.930211268   19.17 18.20     ~ 67 1
13 LBQS 2206-1958A QSO 22 08 52.0729138920 -19 43 59.866776948   17.49 17.33     ~ 216 0
14 QSO B2206-1959 QSO 22 09 00.6950774976 -19 44 19.743416484     18.65     ~ 83 0
15 QSO J2246-6015 QSO 22 47 08.9258659440 -60 15 45.299400480           ~ 70 0

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2023.09.28-12:59:26

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