Classification and Morphology of External Galaxies

Bringing high spatial resolution to the far-infrared

Experimental Astronomy ◽

10.1007/s10686-021-09719-7 ◽

2021 ◽

Author(s):

Hendrik Linz ◽

Henrik Beuther ◽

Maryvonne Gerin ◽

Javier R. Goicoechea ◽

Frank Helmich ◽

...

Keyword(s):

Spatial Resolution ◽

Formation Process ◽

Far Infrared ◽

Main Theme ◽

Spatially Resolved ◽

Research Areas ◽

External Galaxies ◽

Emergence Of Life ◽

Fine Structure Lines

AbstractThe far-infrared (FIR) regime is one of the wavelength ranges where no astronomical data with sub-arcsecond spatial resolution exist. None of the medium-term satellite projects like SPICA, Millimetron, or the Origins Space Telescope will resolve this malady. For many research areas, however, information at high spatial and spectral resolution in the FIR, taken from atomic fine-structure lines, from highly excited carbon monoxide (CO), light hydrides, and especially from water lines would open the door for transformative science. A main theme will be to trace the role of water in proto-planetary discs, to observationally advance our understanding of the planet formation process and, intimately related to that, the pathways to habitable planets and the emergence of life. Furthermore, key observations will zoom into the physics and chemistry of the star-formation process in our own Galaxy, as well as in external galaxies. The FIR provides unique tools to investigate in particular the energetics of heating, cooling, and shocks. The velocity-resolved data in these tracers will reveal the detailed dynamics engrained in these processes in a spatially resolved fashion, and will deliver the perfect synergy with ground-based molecular line data for the colder dense gas.

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AGN Spectra as Seen by the Infrared Space Observatory: First Results

International Astronomical Union Colloquium ◽

10.1017/s0252921100040379 ◽

1997 ◽

Vol 159 ◽

pp. 333-336

Author(s):

D. Lutz ◽

R. Genzel ◽

E. Sturm ◽

A.F.M. Moorwood ◽

E. Oliva ◽

...

Keyword(s):

Fine Structure ◽

Short Wavelength ◽

Molecular Hydrogen ◽

Molecular Gas ◽

Space Observatory ◽

Infrared Space Observatory ◽

First Results ◽

External Galaxies ◽

First Time ◽

Fine Structure Lines

AbstractWe discuss 2.5–45 µm spectra of the Circinus galaxy and of Cen A, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. The large number of detected ionic fine structure lines, observable also in visually obscured sources, provides strong constraints on the shape of the ionizing spectrum, which is found to exhibit a UV bump peaking at ~ 70 eV in the case of Circinus. Pure rotational emission of molecular hydrogen, directly probing warm molecular gas, can for the first time be detected in external galaxies.

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Populations of OB-type stars in galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311010477 ◽

2010 ◽

Vol 6 (S272) ◽

pp. 233-241

Author(s):

Christopher J. Evans

Keyword(s):

Stellar Evolution ◽

Massive Stars ◽

Spectral Synthesis ◽

High Redshift ◽

Young Star ◽

Magellanic Clouds ◽

Star Forming ◽

The Galaxy ◽

External Galaxies

AbstractOne of the challenges for stellar astrophysics is to reach the point at which we can undertake reliable spectral synthesis of unresolved populations in young, star-forming galaxies at high redshift. Here I summarise recent studies of massive stars in the Galaxy and Magellanic Clouds, which span a range of metallicities commensurate with those in high-redshift systems, thus providing an excellent laboratory in which to study the role of environment on stellar evolution. I also give an overview of observations of luminous supergiants in external galaxies out to a remarkable 6.7 Mpc, in which we can exploit our understanding of stellar evolution to study the chemistry and dynamics of the host systems.

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On the Spiral Character of the External Galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/106.3.180 ◽

1946 ◽

Vol 106 (3) ◽

pp. 180-199 ◽

Cited By ~ 4

Author(s):

E. A. Milne

Keyword(s):

External Galaxies

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The AMBRE project: The thick thin disk and thin thick disk of the Milky Way

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731494 ◽

2017 ◽

Vol 608 ◽

pp. L1 ◽

Cited By ~ 23

Author(s):

M. R. Hayden ◽

A. Recio-Blanco ◽

P. de Laverny ◽

S. Mikolaitis ◽

C. C. Worley

Keyword(s):

Vertical Velocity ◽

Velocity Dispersion ◽

Stellar Populations ◽

Thin Disk ◽

Thick Disk ◽

Solar Neighborhood ◽

Chemical Enrichment ◽

History Of ◽

External Galaxies ◽

Subgiant Stars

We analyze 494 main sequence turnoff and subgiant stars from the AMBRE:HARPS survey. These stars have accurate astrometric information from Gaia DR1, providing reliable age estimates with relative uncertainties of ±1 or 2 Gyr and allowing precise orbital determinations. The sample is split based on chemistry into a low-[Mg/Fe] sequence, which are often identified as thin disk stellar populations, and high-[Mg/Fe] sequence, which are often associated with thick disk stellar populations. We find that the high-[Mg/Fe] chemical sequence has extended star formation for several Gyr and is coeval with the oldest stars of the low-[Mg/Fe] chemical sequence: both the low- and high-[Mg/Fe] sequences were forming stars at the same time. We find that the high-[Mg/Fe] stellar populations are only vertically extended for the oldest, most-metal poor and highest [Mg/Fe] stars. When comparing vertical velocity dispersion for the low- and high-[Mg/Fe] sequences, the high-[Mg/Fe] sequence has lower vertical velocity dispersion than the low-[Mg/Fe] sequence for stars of similar age. This means that identifying either group as thin or thick disk based on chemistry is misleading. The stars belonging to the high-[Mg/Fe] sequence have perigalacticons that originate in the inner disk, while the perigalacticons of stars on the low-[Mg/Fe] sequence are generally around the solar neighborhood. From the orbital properties of the stars, the high-[Mg/Fe] and low-[Mg/Fe] sequences are most likely a reflection of the chemical enrichment history of the inner and outer disk populations, respectively; radial mixing causes both populations to be observed in situ at the solar position. Based on these results, we emphasize that it is important to be clear in defining what populations are being referenced when using the terms thin and thick disk, and that ideally the term thick disk should be reserved for purely geometric definitions to avoid confusion and be consistent with definitions in external galaxies.

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