| 51. |
- Aalto, Susanne, 1964
(författare)
-
Molecules as tracers of galaxy evolution
- 2012
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 8:5287, s. 199-208
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Konferensbidrag (refereegranskat)abstract
- Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understandingof the onset and evolution of star formation and the growth of supermassive black holes. Wecan use molecules as observational tools exploiting them as tracers of chemical, physical and dynamicalconditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN, H3O+) in identifyingthe nature of buried activity and its evolution are discussed including some standard astrochemical scenarios.Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminousinfrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscurednuclei, e.g. in the dusty LIRG NGC4418. High resolution studies are often necessary to separate effectsof excitation and radiative transport from those of chemistry - one example is absorption and effects ofstimulated emission in the ULIRG Arp220. Finally, molecular gas in large scale galactic outflows is brieflydiscussed.
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| 52. |
- Aalto, Susanne, 1964, et al.
(författare)
-
OH megamaser emission in the outflow of the luminous infrared galaxy Zw049.057
- 2022
-
Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 18, s. 40-44
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Konferensbidrag (refereegranskat)abstract
- High resolution (0.”26 × 0.”13 (70 × 35 pc)) L-band (18 cm) OH megamaser (OHM) e-Merlin observations of the LIRG Zw049.057 show that the emission is emerging from a low velocity outflowing structure - which is foreground to a fast, dense and collimated molecular outflow detected by ALMA. The extremely dusty compact obscured nucleus (CON) of Zw049.057 has no (or only little) OHM emission associated with it - possibly because of too high number densities that quench the OHM. In contrast we detect 6 cm H2CO emission primarily from the CON-region. We suggest that the OHM-region of Zw049.057 is not directly associated with star formation, but instead occurs in a wide-angle, slow outflow that surrounds the fast and dense outflow. The OHM is pumped by IR emission that likely stems from activities in the nucleus. We briefly discuss how OHM emission can be used as a probe of LIRG-CON galaxies.
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| 53. |
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| 54. |
- Aalto, Susanne, 1964
(författare)
-
Physical conditions and chemistry of molecular gas in galactic centers
- 2014
-
Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 9:S303, s. 15-28
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Tidskriftsartikel (refereegranskat)abstract
- Studying the molecular phase of the interstellar medium in galaxy nuclei is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. The molecular physical conditions in galaxy centers show large variety among galaxies, but in general the average gas densities (traced by e.g.HCN) and temperatures (probed by e.g. H2CO, NH3) are greater than in their disks. Molecular gas and dust is being funneled to the centers of galaxies by spiral arms, bars, and interactions - and one example of this is the minor merger NGC1614. Gas surface densities are also greaterin galaxy nuclei and in extreme cases they become orders of magnitudes larger than what we find in the center of our own Milky Way. We can use IR excited molecular emission to probe the very inner regions of galaxies with deeply obscured nuclei where N(H2)>10^24 cm-2 -for example in the luminous infrared galaxy (LIRG) NGC4418. Abundances of key molecules such as HCN, HCO+, HNC, HC3N, CN, H3O+,are important tools in identifying the nature of buried activity and its evolution. Standard astrochemical scenarios (including X-ray Dominated regions (XDRs) and Photon Dominated Regions (PDRs)) are briefly discussed in this review and how we can use molecules to distinguish between them. High resolution studies are often necessaryto separate effects of excitation and radiative transfer from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. The nuclear activity in luminous galaxies often drives outflows and winds and in some cases molecular gas is being entrained in the outflows. Sometimes the molecular gas is carrying the bulk of the momentum.We can study the structure and physical conditions of the molecular gas to constrain the mass outflow rates and the evolution and nature of the driving source and two examples are discussed here: NGC1377 and Mrk231
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| 55. |
- Aalto, Susanne, 1964, et al.
(författare)
-
Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584
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Tidskriftsartikel (refereegranskat)abstract
- We present high resolution (0.'' 4) IRAM PdBI and ALMA mm and submm observations of the (ultra) luminous infrared galaxies ((U)LIRGs) IRAS 17208-0014, Arp220, IC 860 and Zw049.057 that reveal intense line emission from vibrationally excited (nu(2) = 1) J = 3-2 and 4-3 HCN. The emission is emerging from buried, compact (r 5 x 10(13) L-circle dot kpc(-2). These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, nu(2) = 1, lines of HCN are excited by intense 14 mu m mid-infrared emission and are excellent probes of the dynamics, masses, and physical conditions of (U)LIRG nuclei when H-2 column densities exceed 10(24) cm(-2). It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, we show strong evidence that the ground vibrational state (. = 0), J = 3-2 and 4-3 rotational lines of HCN and HCO+ fail to probe the highly enshrouded, compact nuclear regions owing to strong self-and continuum absorption. The HCN and HCO+ line profiles are double-peaked because of the absorption and show evidence of non-circular motions-possibly in the form of in-or outflows. Detections of vibrationally excited HCN in external galaxies are so far limited to ULIRGs and early-type spiral LIRGs, and we discuss possible causes for this. We tentatively suggest that the peak of vibrationally excited HCN emission is connected to a rapid stage of nuclear growth, before the phase of strong feedback.
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| 56. |
- Aalto, Susanne, 1964
(författare)
-
Probing Molecular Gas Properties in Starbursts and AGNs
- 2005
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Ingår i: in Proceedings of “The Evolution of Starbursts”, Bad Honnef 16-20 August 2004, AIP Conference Proceedings, American Institute of Physics. - 0735402701 ; :783, s. 123-134
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Konferensbidrag (refereegranskat)
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| 57. |
- Aalto, Susanne, 1964, et al.
(författare)
-
The hidden heart of the luminous infrared galaxy IC 860: I. A molecular inflow feeding opaque, extreme nuclear activity
- 2019
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
-
Tidskriftsartikel (refereegranskat)abstract
- High-resolution (0.'03-0.'09 (9-26 pc)) ALMA (100-350 GHz (λ3 to 0.8 mm)) and (0.'04 (11 pc)) VLA 45 GHz measurements have been used to image continuum and spectral line emission from the inner (100 pc) region of the nearby infrared luminous galaxy IC 860. We detect compact (r ∼ 10 pc), luminous, 3 to 0.8 mm continuum emission in the core of IC 860, with brightness temperatures TB > 160 K. The 45 GHz continuum is equally compact but significantly fainter in flux. We suggest that the 3 to 0.8 mm continuum emerges from hot dust with radius r ∼ 8 pc and temperature Td ∼ 280 K, and that it is opaque at millimetre wavelengths, implying a very large H2 column density N(H2)≥ 1026 cm-2. Vibrationally excited lines of HCN v2 = 1f J = 4 - 3 and 3-2 (HCN-VIB) are seen in emission and spatially resolved on scales of 40-50 pc. The line-to-continuum ratio drops towards the inner r = 4 pc, resulting in a ring-like morphology. This may be due to high opacities and matching HCN-VIB excitation- and continuum temperatures. The HCN-VIB emission reveals a north-south nuclear velocity gradient with projected rotation velocities of v = 100 km s-1 at r = 10 pc. The brightest emission is oriented perpendicular to the velocity gradient, with a peak HCN-VIB 3-2 TB of 115 K (above the continuum). Vibrational ground-state lines of HCN 3-2 and 4-3, HC15N 4-3, HCO+ 3-2 and 4-3, and CS 7-6 show complex line absorption and emission features towards the dusty nucleus. Redshifted, reversed P-Cygni profiles are seen for HCN and HCO+ consistent with gas inflow with vin ≤ 50 km s-1. Foreground absorption structures outline the flow, and can be traced from the north-east into the nucleus. In contrast, CS 7-6 has blueshifted line profiles with line wings extending out to -180 km s-1. We suggest that a dense and slow outflow is hidden behind a foreground layer of obscuring, inflowing gas. The centre of IC 860 is in a phase of rapid evolution where an inflow is building up a massive nuclear column density of gas and dust that feeds star formation and/or AGN activity. The slow, dense outflow may be signaling the onset of feedback. The inner, r = 10 pc, IR luminosity may be powered by an AGN or a compact starburst, which then would likely require a top-heavy initial mass function.
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| 58. |
- Aalto, Susanne, 1964, et al.
(författare)
-
Winds of change - a molecular outflow in NGC 1377? The anatomy of an extreme FIR-excess galaxy
- 2012
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 546, s. Article Number: A68-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Our goal was to investigate the molecular gas distribution and kinematics in the extreme far-infrared (FIR) excess galaxy NGC 1377 and to address the nature and evolutionary status of the buried source. Methods. We used high-(0.'' 65 x 0.'' 52, (65 x 52 pc)) and low-(4.'' 88 x 2.'' 93) resolution SubMillimeter Array (SMA) observations to image the (CO)-C-12 and (CO)-C-13 2-1 line emission. Results. We find bright, complex (CO)-C-12 2-1 line emission in the inner 400 pc of NGC 1377. The (CO)-C-12 2-1 line has wings that are tracing a kinematical component that appears to be perpendicular to the component traced by the line core. Together with an intriguing X-shape of the integrated intensity and dispersion maps, this suggests that the molecular emission of NGC 1377 consists of a disk-outflow system. Lower limits to the molecular mass and outflow rate are M-out(H-2) > 1 x 10(7) M-circle dot and (M) over dot > 8 M-circle dot yr(-1). The age of the proposed outflow is estimated to be 1.4 Myr, the extent to be 200 pc and the outflow speed to be V-out = 140 km s(-1). The total molecular mass in the SMA map is estimated to M-tot(H-2) = 1.5 x 10(8) M-circle dot (on a scale of 400 pc) while in the inner r = 29 pc the molecular mass is M-core(H-2) = 1.7 x 10(7) M-circle dot with a corresponding H-2 column density of N(H-2) = 3.4 x 10(23) cm(-2) and an average (CO)-C-12 2-1 brightness temperature of 19 K. (CO)-C-13 2-1 emission is found at a factor 10 fainter than (CO)-C-12 in the low-resolution map while (CO)-O-18 2-1 remains undetected. We find weak 1 mm continuum emission of 2.4 mJy with spatial extent less than 400 pc. Conclusions. Observing the molecular properties of the FIR-excess galaxy NGC 1377 allows us to probe the early stages of nuclear activity and the onset of feedback in active galaxies. The age of the outflow supports the notion that the current nuclear activity is young - a few Myr. The outflow may be powered by radiation pressure from a compact, dust enshrouded nucleus, but other driving mechanisms are possible. The buried source may be an active galactic nucleus (AGN) or an extremely young (1 Myr) compact star-burst. Limitations on size and mass lead us to favor the AGN scenario, but additional studies are required to settle this question. In either case, the wind with its implied mass outflow rate will quench the nuclear power source within the very short time of 5-25 Myr. It is possible, however, that the gas is unable to escape the galaxy and may eventually fall back onto NGC 1377 again.
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| 59. |
- Aapaoja, Aki, et al.
(författare)
-
MaaS service combinations for different geographical areas
- 2017
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Ingår i: 24th World Congress on Intelligent Transportation Systems, Montreal, October 29-November 2, 2017.
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Konferensbidrag (refereegranskat)abstract
- A more efficient use of transport in urban areas and promoting a more sustainable way of living along with ever-accelerating urbanization and digitalization are the main drivers for MaaS. MaaS is needed to solve mobility challenges in cities and new business and service concepts can be easily tested in more densely populated environments first. However, a huge number of people with various demands for mobility services live in smaller communities and rural areas where the availability of and accessibility to mobility services is usually entirely different and more limited than in urban areas. In this paper, MaaS service combinations for four different contexts and geographic areas are identified: 1) MaaS in urban areas; 2) MaaS in suburban areas; 3) MaaS in rural areas; and 4) national and international MaaS. The characteristics of MaaS services in these different geographical areas regarding objectives and included services are also presented.
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| 60. |
- Aarnio, H., et al.
(författare)
-
Photoinduced absorption in an alternating polyfluorene copolymer for photovoltaic applications
- 2006
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Ingår i: Chemical Physics. ; 321:1-2, s. 127-132
-
Tidskriftsartikel (refereegranskat)abstract
- The authors present a detailed study of a novel alternating polyfluorene copolymer, poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3-benzo-thiadiazole)], and its blends with the fullerene deriv. [6,6]-phenyl-C61-butyric acid Me ester, using continuous wave photoinduced absorption (PA) techniques. The authors also present the use of phase information from the PA measurements for estg. the no. of different photoexcitation types present in the PA spectra as well as their lifetimes. In all blends the PA spectra show a broad high-energy PA band ranging from .apprx.1 to 2 eV as well as a low-energy band at .apprx.0.35 eV. The authors find two kinds of excitations present at 80 DegK, polarons showing dispersive recombination with lifetimes of roughly a millisecond, and a 2nd kind of photoexcitation tentatively assigned to coulombically bound intrachain polaron pairs showing practically nondispersive recombination with a lifetime of .apprx.20 ms. [on SciFinder (R)]
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