Dust And Gas Associated With Quasars

Quasars or QSOs,i.e.the accreting black hole engines in galactic nuclei(AGNs),are among the most luminous and violent objects in the universe.The understanding of quasar phenomena is thus important for the study of Galaxies and the physical uni-verse.Despite the large number of AGN sub-classes,the optical emission of quasars are similar,which can be summarised with a steady-state AGN unification model(UM).However,several problems are raised by the UM,such as how materials are accreted from galaxies into the central black holes,and how energetic AGN influence host galax-ies.The key to these problems lies within the flows of substances and energies between black holes and host galaxy reserviors,i.e.AGN inflows and outflows.Unfortunately,the emissions of inflow and outflow gases are frequently immersed in the emission of ex-ceedingly luminous type I quasars and difficult to detect.However,in obscured quasars where nuclear emission is significantly blocked,these flowing gases can be revealed in a much easier way.In obscured AGNs,the blocking material will cause dust extinction and gas-phase absorption to the blackground AGN radiation.The obscuring dust and gas can thus be probed by analysing the extinction curve and absorption lines.On the other hand,ambient clouds can reflect AGN emission into the observers" sightline,making them additional windows of observing AGN emission.And the properties of reflecting clouds can be studied via the scattered light.Based on the physical states,kinematics and chemistry of these obscuring clouds,their roles and functions in quasars can be learned.In this thesis,we present the investigation of extinction,absorption and scatter-ing in four marvellous absorption-line/obscured quasars,and discuss the implication of these methods in similar cases.1)In the peculiar mildly-obscured(EB-V?0.1)quasar J1705+3543 at z?2,a Milky-Way like extinction curve with over 30 metal absorp-tion lines and a Dample Lya absorption(NHI 1020.62cm-2)with broad residual emission are discovered.The dusty absorber is found to have a high metallicy(?3 times solar value),and is redshifted relatively to the quasar at v?[100,500]kms-1.The reasonable explanation to these anomalies is the dusty absorber is intrinsic to the quasar.2)In the heavily obscured narrow-line quasar IRAS F11119+3257,we stud-ied in detail the outflow emission and absorption in ionic and atomic lines.Together with the significant NIR extinction and outflow molecular OH absorption lines in the FIR,we found the position(?4kpc from AGN),mass flow rate(360-1152M(?)yr-1)and kinetic energy flow rate {E??1044-45 erg s-1)of the galactic outflow gas.Consid-ering the violent star formation activity of SFR?600M(?)yr-1,the bulk material of massive outflow should be launched by star formation activity and further accelerated into?1000 kms-1 by the AGN outflow.Similar objects of F11119+3257 demon-strate how black holes regulate host galaxies at large scales.3)In the peculiar narrow emission line Seyfert II(EB-v?10)J1203+1624,we identified the deeply buried NLS1 nucleus(M.= 2.2+0.7-0.5×107M(?),Lbol/LEdd = 2.2+0.6-0.7)through scattered light,and discovered complex inflow-outflow velocity structure of the scattering cloud.And since the AGN is deaply buried,the compact and relatively faint host galaxy is revealed(M*?7.7 × 109M(?),?*= 99±31 kms-1).As an extreme NLS1,J1203+1624 still follows M.?*correlation considering measurement uncertainty.4)In the gas-rich en-vironment around obscured quasars like J1203+1624,scattering can make significant contribution to observed emission.In general cases,however,scattering is much weaker compared to direct AGN emission.Some "Coronagraph" is thus needed to block direct quasar emission to reveal such weak features.In EU V,the lyman limit absorption edges are more frequent natural 'Coronagraphs" compared to dusty absorbers.In the proxi?mate lyman limit absorption edge and sub-DLA tough of z?3.2 quasar J1259+6212,we discovered exceedingly "blue" EUV residual emission around the quasar.By com-paring different models,we found the EUV residual is best explained as scattered ac-cretion disk and BEL emission.And the inferred spectral index is similar to NIR po-larimetry of AGNs,which is consistent with AGN thin-disk model of ?v = +1/3.J1259+6212 shows that lyman absorption edge provide new windows of observing the EUV continuum emission from the innermost of accretion disk.Extinction,absorption and scattering are among key radiative processes to be con-sidered in the studies of intrinsic properties of quasars.On the other hand,the four quasars in this thesis suggest the three phenomenon are crucial in analysing physi-cal states,kinematics and chemistry of gas clouds in quasars and their host galaxies.The MW-like dusty absorber in objects like J705+3543 show us many interesting fea-tures of ISM in quasar environsments,and indicate potential connections between AGN and star-formation activity.In obscured/buried quasar,direct emission from AGN is blocked by dust,which offered us chances to studies weak gas emission at different physical scales in quasars,e.g.the galactic outflow in F11119+3257 and the scatter-ing cloud with outflowing/inflowing velocity structure in J1203+1624.Applying these methods in similar objects might enable us to conduct censuses over gas clouds at dif-ferent scales of quasars.Finally,scattering provide additional windows of observing AGN,which leads to the identification and study of continuum/BEL in type II quasars,and making the easily suppressed AGN EUV emission accessible to the observer for a second chance.Continuing these studies of ISM,outflow,inflow,scattering gas in quasars and probing intrinsic quasar properties in blocked AGNs,we developed sam-ples of these peculiar quasars and will analysis the statistics behind and follow them up,so as to achieve a better understanding of SMBHs,host galaxies and their coevolution.