We studied the properties of the neutral gas in a sample of 38 local luminous and ultra luminous infrared galaxies (ULIRGs, 51 individual galaxies at z ≤ 0.09), which mainly covers the less explored ...LIRG luminosity range. This study is based on the analysis of the spatially integrated and spatially resolved spectra of the NaDλλ 5890, 5896 Å feature obtained with the integral field unit (IFU) of VIMOS at the Very Large Telescope. Analyzing spatially integrated spectra, we find that the contribution of the stars to the observed NaD equivalent width is small (<35%) for about half of the sample, and therefore this feature is dominated by inter stellar medium (ISM) absorption. After subtracting the stellar contribution, we find that the pure-ISM integrated spectra generally show blueshifted NaD profiles, indicating neutral gas outflow velocities, V, in the range 65−260 km s-1. Excluding the galaxies with powerful AGNs, V shows a dependency with the star formation rate (SFR) of the type V ∝ SFR0.15, which is in rather good agreement with previous results. The spatially resolved analysis could be performed for 40 galaxies, 22 of which have neutral gas velocity fields dominated by noncircular motions with signatures of cone-like winds. However, a large number of targets (11/40) show disk rotation signatures. Based on a simple model, we found that the wind masses are in the range 0.4−7.5 × 108 M⊙, reaching up to ~3% of the dynamical mass of the host. The mass rates are typically only ~0.2−0.4 times the corresponding global SFR indicating that, in general, the mass loss is too small to slow down the star formation significantly. In the majority of cases, the velocity of the outflowing gas is not sufficient to escape the host potential well and, therefore, most of the gas rains back into the galaxy disk. On average V/vesc is higher in less massive galaxies, confirming that the galaxy mass has a primary role in shaping the recycling of gas and metals. The comparison between the wind power and kinetic power of the starburst associated with SNe indicates that only the starburst could drive the outflows in nearly all the ULIRGs galaxies, as the wind power is generally lower than 20% of the kinetic power supplied by the starburst. The contribution of an active galactic nuclei (AGN) is, in principle, significant in two cases.
ABSTRACT
Galactic outflows are known to consist of several gas phases; however, the connection between these phases has been investigated little and only in a few objects. In this paper, we analyse ...Multi Unit Spectroscopic Explorer (MUSE)/Very Large Telescope (VLT) data of 26 local (U)LIRGs and study their ionized and neutral atomic phases. We also include objects from the literature to obtain a sample of 31 galaxies with spatially resolved multiphase outflow information. We find that the ionized phase of the outflows has on average an electron density three times higher than the disc (ne,disc ∼ 145 cm−3 versus ne,outflow ∼ 500 cm−3), suggesting that cloud compression in the outflow is more important than 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. This may support models where radiation pressure on dust contributes to driving galactic outflows. 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 ${{\ \rm per\ cent}}$ of the total mass outflow rate in most objects and this fraction is higher in active galactic nuclei (AGN)-dominated systems. The neutral atomic phase contributes of the order of 10 ${{\ \rm per\ cent}}$, while the ionized phase is negligible. The ionized-to-molecular mass outflow rate declines slightly with AGN luminosity, although with a large scatter.
Context.
Arp220 is the nearest and prototypical ultra-luminous infrared galaxy; it shows evidence of pc-scale molecular outflows in its nuclear regions and strongly perturbed ionised gas kinematics ...on kpc scales. It is therefore an ideal system for investigating outflow mechanisms and feedback phenomena in detail.
Aims.
We investigate the feedback effects on the Arp220 interstellar medium (ISM), deriving a detailed picture of the atomic gas in terms of physical and kinematic properties, with a spatial resolution that had never before been obtained (0.56″, i.e. ∼210 pc).
Methods.
We use optical integral-field spectroscopic observations from VLT/MUSE-AO to obtain spatially resolved stellar and gas kinematics, for both ionised (N II
λ
6583) and neutral (Na ID
λ
λ
5891, 96) components; we also derive dust attenuation, electron density, ionisation conditions, and hydrogen column density maps to characterise the ISM properties.
Results.
Arp220 kinematics reveal the presence of a disturbed kpc-scale disc in the innermost nuclear regions as well as highly perturbed multi-phase (neutral and ionised) gas along the minor axis of the disc, which we interpret as a galactic-scale outflow emerging from the Arp220 eastern nucleus. This outflow involves velocities up to ∼1000 km s
−1
at galactocentric distances of ≈5 kpc; it has a mass rate of ∼50
M
⊙
yr
−1
and kinetic and momentum power of ∼10
43
erg s
−1
and ∼10
35
dyne, respectively. The inferred energetics do not allow us to distinguish the origin of the outflows, namely whether they are active galactic nucleus- 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
M
⊙
yr
−1
(i.e. ∼2% of the total SFR).
Conclusions.
Our findings suggest the presence of powerful winds in Arp220: They might be capable of heating or removing large amounts of gas from the host (“negative feedback”) but could also be responsible for triggering star formation (“positive feedback”).
Recent observations have revealed massive galactic molecular outflows that may have the physical conditions (high gas densities) required to form stars. Indeed, several recent models predict that ...such massive outflows may ignite star formation within the outflow itself. This star-formation mode, in which stars form with high radial velocities, could contribute to the morphological evolution of galaxies, to the evolution in size and velocity dispersion of the spheroidal component of galaxies, and would contribute to the population of high-velocity stars, which could even escape the galaxy. Such star formation could provide in situ chemical enrichment of the circumgalactic and intergalactic medium (through supernova explosions of young stars on large orbits), and some models also predict it to contribute substantially to the star-formation rate observed in distant galaxies. Although there exists observational evidence for star formation triggered by outflows or jets into their host galaxy, as a consequence of gas compression, evidence for star formation occurring within galactic outflows is still missing. Here we report spectroscopic observations that unambiguously reveal star formation occurring in a galactic outflow at a redshift of 0.0448. The inferred star-formation rate in the outflow is larger than 15 solar masses per year. Star formation may also be occurring in other galactic outflows, but may have been missed by previous observations owing to the lack of adequate diagnostics.
We analyse the star formation (SF) relations in a sample of 16 nearby luminous infrared galaxies (LIRGs) with more than 2800 regions defined on scales of 90 to 500 pc. We used ALMA to map the ...distribution of the cold molecular gas traced by the
J
= 2–1 line of CO and archival Pa
α
HST/NICMOS imaging to trace the recent SF. In four objects we find two different branches in the Kennicutt-Schmidt relation at 90 pc scales, suggesting the existence of a duality in this relation. The two branches correspond to two different dynamical environments within each galaxy. One branch, which corresponds to the central region of these galaxies (90% of the regions are located at radii < 0.85 kpc), shows higher gas and SF rate surface densities with higher velocity dispersion. The other branch, which shows lower molecular gas and SF rate surface densities, corresponds to the more external disk regions (
r
∼ 1 kpc). Despite the scatter, the SF efficiency of the galaxies with dual behaviour increases with increasing boundedness as measured by the
b
parameter (
b
≡ Σ
H2
/
σ
2
∝
α
vir
−1
). At larger spatial scales (250 and 500 pc), the duality disappears. The rest of the sample does not show evidence of this dual behaviour at any scale.
We present a multi-wavelength integral field spectroscopic (IFS) study of the low-z luminous infrared galaxy IRAS F11506-3851 (ESO 320-G030) on the basis of the moderate spectral resolution ...observations (R ~ 3400−4000) taken with the VIMOS and SINFONI instruments at the ESO VLT. The morphology and the 2D kinematics of the gaseous (neutral and ionized) and stellar components have been mapped in the central regions (<3 kpc) using the NaDλλ5890, 5896 Å absorption doublet, the Hαλ6563 Å line, and the near-IR CO(2–0)λ2.293 μm and CO(3–1)λ2.322 μm bands. The kinematics of the ionized gas and the stars are dominated by rotation, with large observed velocity amplitudes (ΔV(Hα) = 203 ± 4 km s-1; ΔV(CO) = 188 ± 11 km s-1, respectively) and centrally peaked velocity dispersion maps (σc(Hα) = 95 ± 4 km s-1 and σc(CO) = 136 ± 20 km s-1). The stars lag behind the warm gas and represent a dynamically hotter system, as indicated by the observed V/σ ratios (4.5 and 2.4 for the gas and the stars, respectively). Thanks to these IFS data we have disentangled the contribution of the stars and the interstellar medium to the NaD feature, finding that it is dominated by absorption of neutral gas clouds in the interstellar medium (~2/3 of total EW). The 2D kinematics of the neutral gas shows a complex structure dominated by two main components. On the one hand, the thick slowly rotating disk (ΔV(NaD) = 81 ± 12 km s-1) lags significantly compared to the ionized gas and the stars, and it has an irregular and off-center velocity dispersion map (with values of up to ~150 km s-1 at ~1 kpc from the nucleus). On the other hand, a kpc-scale neutral gas outflow perpendicular to the disk, as is revealed by the large blueshifted velocities (in the range 30−154 km s-1) observed along the galaxy’s semi-minor axis (within the inner 1.4 kpc). On the basis of a simple free wind scenario, we derive an outflowing mass rate (Ṁw) in neutral gas of about 48 M⊙ yr-1. Although this implies a global mass loading factor (i.e., η = Ṁw/SFR) of ~1.4, the 2D distribution of the ongoing SF as traced by the Hα emission map suggests a much larger value of η associated with the inner regions (R< 200 pc), where the current observed star formation (SF) represents only ~3 percent of the total. However, the relatively strong emission by supernovae in the central regions, as traced by the FeII emission, indicates recent strong episodes of SF. Therefore, our data show clear evidence of the presence of a strong outflow with large loading factors associated with the nuclear regions, where recent starburst activity took place about 7 Myr ago, although it currently shows relatively modest SF levels. All together these results strongly suggest that we are witnessing (nuclear) quenching due to SF feedback in IRAS F11506-3851. However, the relatively large mass of molecular gas detected in the nuclear region via the H2 1−0S(1) line suggests that further episodes of SF may take place again.
Optical spectroscopy of type 2 LINERs Hermosa Muñoz, L.; Cazzoli, S.; Márquez, I. ...
Astronomy and astrophysics (Berlin),
03/2020, Letnik:
635
Journal Article
Recenzirano
Odprti dostop
Context. Type 2 Low-ionization Nuclear Emission-line Regions (LINERs) have been optically classified with the Palomar data as not presenting a broad component in the Balmer emission lines that are ...associated with the broad-line region (BLR) of the active galactic nuclei (AGN). Aims. We aim to unveil the presence of different kinematic components of emission lines in the nuclear region of a sample of local ( z ≤ 0.022) type 2 LINERs. We focus on the analysis of the true nature of LINERs by means of the detection (or nondetection) of a broad component that originated in the BLR of the AGN. Additionally, we search for the possible presence of nonrotational motions such as outflows in these LINERs. Methods. We applied a decomposition of the nuclear emission lines using an spectroscopic analysis of the optical spectra of nine type 2 LINERs of intermediate-resolution spectroscopic data retrieved from the Hubble Space Telescope (HST) archive. The study is completed with archival spectra from the Double Spectrograph from the Palomar Observatory. Results. The emission line fitting reveals the presence of a broad component associated with the BLR in six out of the nine galaxies for the space-based data, and for two out of the eight from the ground-based spectra. The velocity dispersion for two galaxies (NGC 4486 and NGC 4594) measured in HST/STIS data suggest the presence of outflows. Conclusions. The results indicate that the spatial resolution plays a major role in the detection of the BLR, as it appears diluted in the ground-based data (even after removing stellar contribution). This is also true for the emission line diagnostics, as the contaminant light contributes to lower emission line ratios toward the star-forming area of standard BPTs. We propose to reclassify NGC 4594 as a type 1 LINER, since a BLR component is seen in both space- and ground-based spectra. We find ambiguous results for the BLR component of NGC 4486. The modest outflow detection in our sample may indicate that they are not as frequent as seen for type 1 LINERs.
Abstract
Jets (fast collimated outflows) are claimed to be the main shaping agent of the most asymmetric planetary nebulae (PNs), as they impinge on the circumstellar material at late stages of the ...asymptotic giant branch phase. The first jet detected in a PN was that of NGC 2392, yet there is no available image because of its low surface brightness contrast with the bright nebular emission. Here we take advantage of the tomographic capabilities of Gran Telescopio de Canarias Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía high-dispersion integral field spectroscopic observations of the jet in NGC 2392 to gain unprecedented details of its morphology and kinematics. The jet of NGC 2392 is found to emanate from the central star, break through the walls of the inner shell of this iconic PN and extend outside the nebula’s outermost regions with an S-shaped morphology suggestive of precession. At odds with the fossil jets found in mature PNs, the jet in NGC 2392 is currently being collimated and launched. The high nebular excitation of NGC 2392, which implies an He
++
/He ionization fraction too high to be attributed to the known effective temperature of the star, has been proposed in the past to hint at the presence of a hot white dwarf companion. In conjunction with the hard X-ray emission from the central star, the present-day jet collimation would support the presence of such a double-degenerate system where one component undergoes accretion from a remnant circumbinary disk of the common envelope phase.
ABSTRACT
The central star of the planetary nebula (PN) HuBi 1 has been recently proposed to have experienced a very late thermal pulse (VLTP), but the dilution of the emission of the recent ejecta by ...that of the surrounding H-rich old outer shell has so far hindered confirming its suspected H-poor nature. We present here an analysis of the optical properties of the ejecta in the innermost regions of HuBi 1 using MEGARA high-dispersion integral field and OSIRIS intermediate-dispersion long-slit spectroscopic observations obtained with the 10.4-m Gran Telescopio de Canarias. The unprecedented tomographic capability of MEGARA to resolve structures in velocity space allowed us to disentangle for the first time the Hα and Hβ emission of the recent ejecta from that of the outer shell. The recent ejecta is found to have much higher extinction than the outer shell, implying the presence of large amounts of dust. The spatial distribution of the emission from the ejecta and the locus of key line ratios in diagnostic diagrams probe the shock excitation of the inner ejecta in HuBi 1, in stark contrast with the photoionization nature of the H-rich outer shell. The abundances of the recent ejecta have been computed using the mappings v code under a shock scenario. They are found to be consistent with a born-again ejection scenario experienced by the progenitor star, which is thus firmly confirmed as a new ‘born-again’ star.
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