18 research outputs found
Widespread QSO-driven outflows in the early Universe
We present the stacking analysis of a sample of 48 quasi-stellar objects (QSOs) at 4.5 < z < 7.1 detected by the Atacama Large
Millimetre Array (ALMA) in the [CII] \u3bb158 \ub5m emission line to investigate the presence and the properties of massive, cold outflows
associated with broad wings in the [CII] profile. The high sensitivity reached through this analysis allows us to reveal very broad
[CII] wings tracing the presence of outflows with velocities in excess of 1000 km s 121. We find that the luminosity of the broad [CII]
emission increases with LAGN, while it does not significantly depend on the star formation rate of the host galaxy, indicating that the
central active galactic nucleus (AGN) is the main driving mechanism of the [CII] outflows in these powerful, distant QSOs. From
the stack of the ALMA cubes, we derive an average outflow spatial extent of 3c3.5 kpc. The average atomic neutral mass outflow rate
inferred from the stack of the whole sample is M\u2d9out 3c 100 M yr 121, while for the most luminous systems it increases to 3c200 M yr 121.
The associated outflow kinetic power is about 0.1% of LAGN, while the outflow momentum rate is 3cLAGN/c or lower, suggesting that
these outflows are either driven by radiation pressure onto dusty clouds or, alternatively, are driven by the nuclear wind and energy
conserving but with low coupling with the interstellar medium. We discuss the implications of the resulting feedback effect on galaxy
evolution in the early Universe
Widespread {QSO}-driven outflows in the early Universe
We present the stacking analysis of a sample of 48 quasi-stellar objects (QSOs) at 4.5 < z < 7.1 detected by the Atacama Large Millimetre Array (ALMA) in the [CII] lambda 158 mu m emission line to investigate the presence and the properties of massive, cold outflows associated with broad wings in the [CII] profile. The high sensitivity reached through this analysis allows us to reveal very broad [CII] wings tracing the presence of outflows with velocities in excess of 1000 km s(-1). We find that the luminosity of the broad [CII] emission increases with L-AGN, while it does not significantly depend on the star formation rate of the host galaxy, indicating that the central active galactic nucleus (AGN) is the main driving mechanism of the [CII] outflows in these powerful, distant QSOs. From the stack of the ALMA cubes, we derive an average outflow spatial extent of similar to 3.5 kpc. The average atomic neutral mass outflow rate inferred from the stack of the whole sample is (M)over dot(out) similar to 100 M-circle dot yr(-1), while for the most luminous systems it increases to similar to 200 M(circle dot)yr(-1). The associated outflow kinetic power is about 0.1% of LAGN, while the outflow momentum rate is similar to L-AGN/C or lower, suggesting that these outflows are either driven by radiation pressure onto dusty clouds or, alternatively, are driven by the nuclear wind and energy conserving but with low coupling with the interstellar medium. We discuss the implications of the resulting feedback effect on galaxy evolution in the early Universe
Cold molecular outflows in the local Universe and their feedback effect on galaxies
We study molecular outflows in a sample of 45 local galaxies, both star
forming and AGN, primarily by using CO data from the ALMA archive and from the
literature. For a subsample we also compare the molecular outflow with the
ionized and neutral atomic phases. We infer an empirical analytical function
relating the outflow rate simultaneously to the SFR, , and galaxy
stellar mass; this relation is much tighter than the relations with the
individual quantities. The outflow kinetic power shows a larger scatter than in
previous, more biased studies, spanning from 0.1 to 5 per cent of , while the momentum rate ranges from 1 to 30 times ,
indicating that these outflows can be both energy-driven, but with a broad
range of coupling efficiencies with the ISM, and radiation pressure-driven. For
about 10 per cent of the objects the outflow energetics significantly exceed
the maximum theoretical values; we interpret these as 'fossil outflows'
resulting from activity of a past strong AGN, which has now faded. We estimate
that, in the stellar mass range probed here ( 10), less
than 5 per cent of the outflowing gas escapes the galaxy. The molecular gas
depletion time associated with the outflow can be as short as a few million
years in powerful AGN, however, the total gas (H+HI) depletion times are
much longer. Altogether, our findings suggest that even AGN-driven outflows
might be relatively ineffective in clearing galaxies of their entire gas
content, although they are likely capable of clearing and quenching the central
region
MUSE view of Arp220: Kpc-scale multi-phase outflow and evidence for positive feedback
Arp220 is the nearest and prototypical ULIRG, and shows evidence of pc-scale
molecular outflows in its nuclear regions and strongly perturbed ionised gas
kinematics on kpc scales. It is therefore the ideal system for investigating
outflows and feedback phenomena in details. We investigate the feedback effects
on the Arp220 ISM, deriving a detailed picture of the atomic gas in terms of
physical and kinematic properties, with a spatial resolution never obtained
before (0.56", i.e. ~ 210 pc). We use optical IFS observations from VLT/MUSE-AO
to obtain spatially resolved stellar and gas kinematics, for both ionised ([N
II]6583) and neutral (Na ID5891,96) components; we also derive dust
attenuation, electron density, ionisation conditions and hydrogen column
density maps to characterise the ISM properties. Arp220 kinematics reveal the
presence of a disturbed, kpc-scale disk in the innermost nuclear regions, and
highly perturbed, multi-phase (neutral and ionised) gas along the minor-axis of
the disk, which we interpret as a galactic-scale outflow emerging from the
Arp220 eastern nucleus. This outflow involves velocities up to ~ 1000 km/s at
galactocentric distances of ~ 5 kpc, and has a mass rate of ~ 50 Msun/yr, and
kinetic and momentum power of ~ 1e43 erg/s and ~ 1e35 dyne, respectively. The
inferred energetics do not allow us to distinguish the origin of the outflows,
i.e. whether they are AGN-driven or starburst-driven. We also present evidence
for enhanced star formation at the edges of - and within - the outflow, with a
star formation rate SFR ~ 5 Msun/yr (i.e. ~ 2% of the total SFR). Our findings
suggest the presence of powerful winds in Arp220: they might be capable of
removing or heating large amounts of gas from the host ("negative feedback"),
but could be also responsible for triggering star formation ("positive
feedback").STFC
ER
Properties of the multiphase outflows in local (ultra)luminous infrared galaxies
Galactic outflows are known to consist of several gas phases, however, so far
the connection between these multiple phases has been investigated little and
only in a few objects. In this paper, we analyse MUSE/VLT data of 26 local
(U)LIRGs and study their ionised and neutral atomic phases. We also include
objects from the literature to obtain a total sample of 31 galaxies with
spatially resolved multi-phase outflow information. We find that the ionized
phase of the outflows has on average an electron density three times higher
than the disc ( 150 cm vs
500 cm), suggesting that cloud compression in the outflow is more
important that cloud dissipation. We find that the difference in extinction
between outflow and disc correlates with the outflow gas mass. Together with
the analysis of the outflow velocities, this suggests that at least some of the
outflows are associated with the ejection of dusty clouds from the disc. The
presence of dust in outflows is relevant for potential formation of molecules
inside them. We combine our data with millimetre data to investigate the
molecular phase. We find that the molecular phase accounts for more than 60
of the total mass outflow rate in most objects and this fraction is higher
in AGN-dominated systems. The neutral atomic phase contributes of the order of
10 , while the ionized phase is negligible. The ionized-to-molecular mass
outflow rate declines slightly with AGN luminosity, although with a large
scatter.STFC
ER
AGN-driven outflows in the early Universe
The origin of the tight correlations observed between the masses of supermassive black holes (SMBHs) and host galaxy properties is still debated. Negative feedback from AGN can provide a viable explanation for these correlations. According to the theoretical models, the ejective feedback resulting from radiatively-efficient episodes of gas accretion onto SMBHs may be the main responsible for the rapid shut-off of star formation and black hole growth in the early stages of the evolution of present-day massive galaxies, which must have taken place at z>2. Here we present near-IR (SINFONI) and millimetre (ALMA) observations of z~2.5 luminous (Lbol>1e47 Lsun) quasars showing fast and extended ionised outflows. These AGN-driven outflows appear to be able to expel a large fraction of molecular and ionised gas and suppress star formation in the outflow region. However, the detection of Halpha emission along the edges of the outflow cone indicates on-going star formation rates of at least 50 Msun/yr, suggesting either that AGN feedback does not affect the whole galaxy or that many feedback episodes are required before star formation is completely quenched. On the other hand, the detection also lead to a positive feedback interpretation: the AGN-driven outflow compress the surrounding gas inducing star formation. Our results highlight the possible double role of galaxy-wide outflows in host galaxy evolution. This is also supported by recent observations in the local Universe indicate that massive galactic outflows may ignite star formation within the outflow itself. We also present new ALMA observations of a sample of quasars at z∼6 optimised to investigate the extended emission associated with outflows as traced by the [CII]158μm line. Although strong and powerful AGN-driven outflows are expected at these redshifts, our analysis suggests that such outflows may not be as effective as expected in removing gas out of their host galaxies
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Cold molecular outflows in the local Universe and their feedback effect on galaxies
We study molecular outflows in a sample of 45 local galaxies, both star
forming and AGN, primarily by using CO data from the ALMA archive and from the
literature. For a subsample we also compare the molecular outflow with the
ionized and neutral atomic phases. We infer an empirical analytical function
relating the outflow rate simultaneously to the SFR, , and galaxy
stellar mass; this relation is much tighter than the relations with the
individual quantities. The outflow kinetic power shows a larger scatter than in
previous studies, spanning from 0.1 to 5~per cent of , while the
momentum rate ranges from 1 to 30 times , indicating that these
outflows can be both energy-driven, but with a broad range of coupling
efficiencies with the ISM, and radiation pressure-driven. For about 10~per cent
of the objects the outflow properties significantly exceed the maximum
theoretical values; we interpret these as "fossil outflows" resulting from
activity of a past strong AGN, which has now faded. We estimate that, in the
stellar mass range probed here ( 10), less than 5~per
cent of the outflowing gas escapes the galaxy. The molecular gas depletion time
associated with the outflow can be as short as a few million years in powerful
AGNs, however the total gas (H+HI) depletion times are much longer.
Altogether, our findings suggest that even AGN-driven outflows might be
relatively ineffective in clearing galaxies of their entire gas content,
although they are likely capable of clearing and quenching the central region.
Finally, we find no correlation between molecular outflow rate and radio power,
suggesting that on average radio jets do not play a major role in driving
massive molecular outflows in the luminosity range (log() = 41-46
erg s) probed here
Cold molecular outflows in the local Universe and their feedback effect on galaxies
Large scale structure and cosmolog
Nesting Behavior of the Poo-uli
Volume: 108Start Page: 620End Page: 63
Molecular outflows in local galaxies: Method comparison and a role of intermittent AGN driving
We report new detections and limits from a NOEMA and ALMA CO(1-0) search for
molecular outflows in 13 local galaxies with high FIR surface brightness, and
combine with results from the literature. CO line ratios and outflow structure
provide some constraints on the conversion from observables to quantities such
as molecular mass outflow rates. Ratios between outflow emission in higher J CO
transitions and in CO(1-0) typically are consistent with excitation Ri1<~1. For
IRAS 13120-5453, however, R31=2.10 indicates optically thin CO in the outflow.
Like much of the outflow literature, we use alpha(CO) = 0.8, and we present
arguments for using C=1 in deriving molecular mass outflow rates Mdot =
C*M*v/R. We compare the two main methods for molecular outflow detection: CO mm
interferometry and Herschel OH spectroscopy. For 26 sources studied with both
methods, we find 80% agreement in detecting vout>~150km/s outflows, and
non-matches can be plausibly ascribed to outflow geometry and SNR. For 12
bright ULIRGs with detailed OH-based outflow modeling, CO outflows are detected
in all but one. Outflow masses, velocities, and sizes for these 11 sources
agree well between the two methods, and modest remaining differences may relate
to the different but overlapping regions sampled by CO emission and OH
absorption. Outflow properties correlate better with AGN luminosity and with
bolometric luminosity than with FIR surface brightness. The most massive
outflows are found for systems with current AGN activity, but significant
outflows in non-AGN systems must relate to star formation or to AGN activity in
the recent past. We report scaling relations for the increase of outflow mass,
rate, momentum rate, and kinetic power with bolometric luminosity. Short
~10^6yr flow times and some sources with resolved multiple outflow episodes
support a role of intermittent driving, likely by AGN. (abridged)ER