scholarly journals Hidden or missing outflows in highly obscured galaxy nuclei?

2019 ◽  
Vol 623 ◽  
pp. A29 ◽  
Author(s):  
N. Falstad ◽  
F. Hallqvist ◽  
S. Aalto ◽  
S. König ◽  
S. Muller ◽  
...  
Keyword(s):  
Line Emission ◽  
Far Infrared ◽  
Spectral Lines ◽  
Absorption Lines ◽  
Wide Angle ◽  
Vibrationally Excited ◽  
Molecular Outflows ◽  
Luminous Infrared Galaxies ◽  
The Galaxy ◽  
Central Regions

Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed. Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs). Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs. Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH. Conclusions. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

scholarly journals Hidden molecular outflow in the LIRG Zw 049.057

2018 ◽  
Vol 609 ◽  
pp. A75 ◽  
Author(s):  
N. Falstad ◽  
S. Aalto ◽  
J. G. Mangum ◽  
F. Costagliola ◽  
J. S. Gallagher ◽  
...  
Keyword(s):  
Far Infrared ◽  
Minor Axis ◽  
Spectral Lines ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Nuclear Activity ◽  
Molecular Outflow ◽  
The Galaxy ◽  
Excitation Conditions

Context. Feedback in the form of mass outflows driven by star formation or active galactic nuclei is a key component of galaxy evolution. The luminous infrared galaxy Zw 049.057 harbours a compact obscured nucleus with a possible far-infrared signature of outflowing molecular gas. Due to the high optical depths at far-infrared wavelengths, however, the interpretation of the outflow signature is uncertain. At millimeter and radio wavelengths, the radiation is better able to penetrate the large columns of gas and dust responsible for the obscuration. Aims. We aim to investigate the molecular gas distribution and kinematics in the nucleus of Zw 049.057 in order to confirm and locate the molecular outflow, with the ultimate goal to understand how the nuclear activity affects the host galaxy. Methods. We used high angular resolution observations from the Submillimeter Array (SMA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Karl G. Jansky Very Large Array (VLA) to image the CO J = 2–1 and J = 6–5 emission, the 690 GHz continuum, the radio centimeter continuum, and absorptions by rotationally excited OH. Results. The CO line profiles exhibit wings extending ~ 300 km s-1 beyond the systemic velocity. At centimeter wavelengths, we find a compact (~ 40 pc) continuum component in the nucleus, with weaker emission extending several 100 pc approximately along the major and minor axes of the galaxy. In the OH absorption lines toward the compact continuum, wings extending to a similar velocity as for the CO are only seen on the blue side of the profile. The weak centimeter continuum emission along the minor axis is aligned with a highly collimated, jet-like dust feature previously seen in near-infrared images of the galaxy. Comparison of the apparent optical depths in the OH lines indicate that the excitation conditions in Zw 049.057 differ from those within other OH megamaser galaxies. Conclusions. We interpret the wings in the spectral lines as signatures of a nuclear molecular outflow. A relation between this outflow and the minor axis radio feature is possible, although further studies are required to investigate this possible association and understand the connection between the outflow and the nuclear activity. Finally, we suggest that the differing OH excitation conditions are further evidence that Zw 049.057 is in a transition phase between megamaser and kilomaser activity.

scholarly journals AHerschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies

2017 ◽  
Vol 846 (1) ◽  
pp. 32 ◽  
Author(s):  
T. Díaz-Santos ◽  
L. Armus ◽  
V. Charmandaris ◽  
N. Lu ◽  
S. Stierwalt ◽  
...  
Keyword(s):  
Line Emission ◽  
Far Infrared ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies

scholarly journals What did the seahorse swallow? APEX 170 GHz observations of the chemical conditions in the Seahorse infrared dark cloud

2020 ◽  
Vol 639 ◽  
pp. A65 ◽  
Author(s):  
O. Miettinen
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Line Emission ◽  
Spectral Lines ◽  
Absorption Lines ◽  
High Mass ◽  
Mass Star ◽  
Evolutionary Trends ◽  
Detection Rates ◽  
Molecular Abundances

Context. Infrared dark clouds (IRDCs) are useful target sources for the studies of molecular cloud substructure evolution and early stages of star formation. Determining the chemical composition of IRDCs helps to constrain the initial conditions and timescales (via chemical clocks) of star formation in these often filamentary, dense interstellar clouds. Aims. We aim to determine the fractional abundances of multiple different molecular species in the filamentary IRDC G304.74+01.32, nicknamed the Seahorse IRDC, and to search for relationships between the abundances and potential evolutionary trends. Methods. We used the Atacama Pathfinder EXperiment (APEX) telescope to observe spectral lines occurring at about 170 GHz frequency towards 14 positions along the full extent of the Seahorse filament. The sample is composed of five clumps that appear dark in the mid-IR, eight clumps that are associated with mid-IR sources, and one clump that is already hosting an H II region and is, hence, likely to be in the most advanced stage of evolution of all the target sources. We also employed our previous 870 μm dust continuum imaging data of the Seahorse. Results. Six spectral line transitions were detected (≥3σ) altogether, namely, SO(NJ = 44−33), H13CN(J = 2−1), H13CO+(J = 2−1), SiO(J = 4−3), HN13C(J = 2−1), and C2H(N = 2−1). While SO, H13CO+, and HN13C were detected in every source, the detection rates for C2H and H13CN were 92.9 and 85.7%, respectively. Only one source (SMM 3) showed detectable SiO emission (7.1% detection rate). Three clumps (SMM 5, 6, and 7) showed the SO, H13CN, H13CO+, HN13C, and C2H lines in absorption. Of the detected species, C2H was found to be the most abundant one with respect to H2 (a few times 10−9 on average), while HN13C was found to be the least abundant species (a few times 10−11). We found three positive correlations among the derived molecular abundances, of which those between C2H and HN13C and HN13C and H13CO+ are the most significant (correlation coefficient r ≃ 0.9). The statistically most significant evolutionary trends we uncovered are the drops in the C2H abundance and in the [HN13C]∕[H13CN] ratio as the clump evolves from an IR dark stage to an IR bright stage and then to an H II region. Conclusions. The absorption lines detected towards SMM 6 and SMM 7 could arise from continuum radiation from an embedded young stellar object and an extragalactic object seen along the line of sight. However, the cause of absorption lines in the IR dark clump SMM 5 remains unclear. The correlations we found between the different molecular abundances can be understood as arising from the gas-phase electron (ionisation degree) and atomic carbon abundances. With the exception of H13CN and H13CO+, the fractional abundances of the detected molecules in the Seahorse are relatively low compared to those in other IRDC sources. The [C2H] evolutionary indicator we found is in agreement with previous studies, and can be explained by the conversion of C2H to other species (e.g. CO) when the clump temperature rises, especially after the ignition of a hot molecular core in the clump. The decrease of [HN13C]∕[H13CN] as the clump evolves is also likely to reflect the increase in the clump temperature, which leads to an enhanced formation of HCN and its 13C isotopologue. Both single-dish and high-resolution interferometric imaging of molecular line emission (or absorption) of the Seahorse filament are required to understand the large-scale spatial distribution of the gas and to search for possible hot, high-mass star-forming cores in the cloud.

scholarly journals Spectral Line Observations of the Galactic Centre Region

1977 ◽  
Vol 45 ◽  
pp. 119-120
Author(s):  
R. D. Davies ◽  
R. J. Cohen
Keyword(s):  
Velocity Field ◽  
Spectral Line ◽  
Angular Resolution ◽  
Spectral Lines ◽  
Galactic Centre ◽  
Radio Telescopes ◽  
Gas Distribution ◽  
The Galaxy ◽  
Central Regions ◽  
Centre Region

An investigation of the central regions of the Galaxy has been made with an angular resolution of ~10 arcmin with the radio telescopes at Jodrell Bank using the spectral lines of HI (λ21 cm), OH (λ18 cm) and H2CO (λ6 cm). Observations of radio recombination lines in the range (λ21 to 125 cm) have also been taken. These data taken together provide information on the velocity field and gas distribution in the galactic centre region. A continuing programme of spectral line observations of the galactic centre is being pursued at Jodrell Bank.

scholarly journals A Spectroscopic Study of Supernova Remnants with the Infrared Space Observatory*

2021 ◽  
Vol 257 (2) ◽  
pp. 36
Author(s):  
Matthew J. Millard ◽  
Aravind P. Ravi ◽  
Jeonghee Rho ◽  
Sangwook Park
Keyword(s):  
Supernova Remnants ◽  
Crab Nebula ◽  
Line Emission ◽  
Far Infrared ◽  
Atomic Emission ◽  
Extensive Study ◽  
Space Observatory ◽  
Infrared Space Observatory ◽  
The Galaxy ◽  
The Crab Nebula

Abstract We present far-infrared (FIR) spectroscopy of supernova remnants (SNRs) based on the archival data of the Infrared Space Observatory taken with the Long Wavelength Spectrometer (LWS). Our sample includes previously unpublished profiles of line and continuum spectra for 20 SNRs in the Galaxy and Magellanic Clouds. In several SNRs including G21.5–0.9, G29.7–0.3, the Crab Nebula, and G320.4–1.2, we find evidence for broad [O i], [O iii], [N ii], and [C ii] lines with velocity dispersions up to a few 103 km s−1, indicating that they are associated with high-velocity SN ejecta. Our detection of Doppler-broadened atomic emission lines and a bright FIR continuum hints at the presence of newly formed dust in SN ejecta. For G320.4–1.2, we present the first estimate of an ejecta-dust mass of 0.1–0.2 M ⊙, which spatially coincides with the broad-line emission, by applying a blackbody model fit with components of the SNR and background emission. Our sample includes raster maps of 63 μm, 145 μm [O i], and 158 μm [C ii] lines toward SNRs Kes 79, CTB 109, and IC 443. Based on these line intensities, we suggest interacting shock types in these SNRs. Finally, we compare our LWS spectra of our sample SNRs with the spectra of several H ii regions, and discuss their FIR line intensity ratios and continuum properties. Follow-up observations with modern instruments (e.g., JWST and SOFIA) with higher spatial and spectral resolution are encouraged for an extensive study of the SN ejecta and the SN dust.

scholarly journals Vibrationally Excited HC3N in NGC 4418

2009 ◽  
Vol 5 (H15) ◽  
pp. 421-422
Author(s):  
F. Costagliola ◽  
S. Aalto
Keyword(s):  
Galaxy Formation ◽  
Infrared Region ◽  
Power Source ◽  
Energy Output ◽  
Infrared Galaxies ◽  
Vibrationally Excited ◽  
Luminous Infrared Galaxies ◽  
Galaxy Formation And Evolution ◽  
Central Regions ◽  
Formation And Evolution

Luminous infrared galaxies (LIRGs) emit most of their radiation in the infrared region of the spectrum in the form of dust thermal continuum, with typical luminosities of LIR > 1010 L⊙. The central power source responsible for the total energy output is deeply buried in the dusty central regions of these objects and its origin still unclear. Recent studies by Spoon et al. (2007) and Aalto et al. (2007) suggest that some LIRGs might represent early obscured stages of active galaxies, either AGNs or starbursts, and thus play a fundamental role in galaxy formation and evolution.

scholarly journals Herschel spectroscopy of massive young stellar objects in the Magellanic Clouds

2019 ◽  
Vol 490 (3) ◽  
pp. 3909-3935
Author(s):  
J M Oliveira ◽  
J Th van Loon ◽  
M Sewiło ◽  
M-Y Lee ◽  
V Lebouteiller ◽  
...  
Keyword(s):  
Line Emission ◽  
Far Infrared ◽  
Magellanic Clouds ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Heating Efficiency ◽  
Photodetector Array ◽  
The Galaxy ◽  
Low Metallicity ◽  
Ir Emission

ABSTRACT We present Herschel Space Observatory Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE FTS) spectroscopy of a sample of 20 massive Young Stellar Objects (YSOs) in the Large and Small Magellanic Clouds (LMC and SMC). We analyse the brightest far-infrared (far-IR) emission lines, that diagnose the conditions of the heated gas in the YSO envelope and pinpoint their physical origin. We compare the properties of massive Magellanic and Galactic YSOs. We find that [O i] and [C ii] emission, that originates from the photo-dissociation region associated with the YSOs, is enhanced with respect to the dust continuum in the Magellanic sample. Furthermore the photoelectric heating efficiency is systematically higher for Magellanic YSOs, consistent with reduced grain charge in low metallicity environments. The observed CO emission is likely due to multiple shock components. The gas temperatures, derived from the analysis of CO rotational diagrams, are similar to Galactic estimates. This suggests a common origin to the observed CO excitation, from low-luminosity to massive YSOs, both in the Galaxy and the Magellanic Clouds. Bright far-IR line emission provides a mechanism to cool the YSO environment. We find that, even though [O i], CO, and [C ii] are the main line coolants, there is an indication that CO becomes less important at low metallicity, especially for the SMC sources. This is consistent with a reduction in CO abundance in environments where the dust is warmer due to reduced ultraviolet-shielding. Weak H2O and OH emission is detected, consistent with a modest role in the energy balance of wider massive YSO environments.

scholarly journals Diffuse [CII] Emission in the Galaxy

1996 ◽  
Vol 169 ◽  
pp. 497-498
Author(s):  
H. Okuda ◽  
T. Nakagawa ◽  
H. Shibai ◽  
Y. Doi ◽  
K. Mochizuki ◽  
...  
Keyword(s):  
Intensity Distribution ◽  
Emission Intensity ◽  
Galactic Center ◽  
Galactic Plane ◽  
Line Emission ◽  
Far Infrared ◽  
Extensive Survey ◽  
The Galaxy ◽  
Infrared Continuum ◽  
Tangential Directions

An extensive survey of [C II] line emission at 158 microns using the balloon borne telescope (BICE) has provided a complete map of the emission intensity distribution in the first and the fourth quadrants of the galactic plane (280° < l < 80°, −5° < b < 5°: Okuda et al. 1993). The emission is very extended throughout the galactic plane in which three intensity maxima are seen towards the tangential directions of the Scutum and the Norma arms as well as in the Galactic center region. However the Galactic center maximum is much less prominent compared with the two other distributions, unlike the case of far infrared continuum and CO emissions.

scholarly journals The Heating of Interstellar Gas by Dust

1989 ◽  
Vol 135 ◽  
pp. 227-238 ◽  
Author(s):  
David J. Hollenbach
Keyword(s):  
Radiant Energy ◽  
Line Emission ◽  
Far Infrared ◽  
Infrared Emission ◽  
Interstellar Gas ◽  
Vibrationally Excited ◽  
Gas Heating ◽  
Ultraviolet Photons ◽  
Diffuse Clouds ◽  
Infrared Continuum

Interstellar grains serve as an intermediary in transferring stellar radiant energy or gas chemical energy into the heating of interstellar gas. Grain photoelectric heating, a process in which ultraviolet photons eject energetic electrons from grains into the gas, dominates the gas heating of the intercloud medium, diffuse clouds, and most photodissociation regions (PDRs); it is also significant in HII regions. Grain photoelectric heating in PDRs can explain the observed correlations of CII(158 μm) with CO J=1-0 intensities and CII(158 μm) + OI(63 μm) with infrared continuum (grain) luminosities. Gas-grain collisions and the infrared emission from grains can dominate the gas heating in molecular clouds with embedded stars. The ejection of newly-formed, vibrationally-excited H2 molecules from grains behind dense, dissociative shocks leads to postshock gas heating which produces strong far-infrared and millimeter line emission as well as H2O maser emission.

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