Diffuse Interstellar Bands in Emission

AbstractRecent Fabry-Pérot observations towards the galaxy NGC 1325 with the Southern African Large Telescope (SALT) led to the serendipitous discovery of an emission feature centered at 661.3 nm arising from material in the interstellar medium (ISM) of our Galaxy; this emission feature lies at the wavelength of one of the sharper and stronger diffuse bands normally seen in absorption. The flux of the feature is 4.2 ± 0.5 × 10−18 es−1 cm−2 arcsec−2. It appears that this is the first observation of emission from a diffuse band carrier in the ISM, excited in this case by the interstellar radiation field. We present the discovery spectra and describe follow-up measurements proposed for SALT.

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ROSAT Observations of NGC 4258

International Astronomical Union Colloquium ◽

10.1017/s025292110007158x ◽

1997 ◽

Vol 166 ◽

pp. 547-550

Author(s):

Andreas Vogler ◽

Wolfgang Pietsch

Keyword(s):

Interstellar Medium ◽

Point Source ◽

Brightness Temperature ◽

Spiral Galaxy ◽

Surface Brightness ◽

Point Sources ◽

X Rays ◽

X Ray ◽

The Galaxy

AbstractWe performed deep follow up observations of the active spiral galaxy NGC 4258 with the ROSAT HRI and PSPC to study the different emission components. The overall luminosity of NGC 4258 is Lx ~ 2 × 1040 erg s−1 in the 0.1 – 2.4 keV ROSAT band. Besides a weak nuclear point source (Lx ≲ 1038 erg s−1) fourteen point sources are detected in the NGC 4258 disk (integral Lx ~ 3 × 1039 erg s− 1). The bulk of the X-ray emission is not resolved. The main contributions are explained by hot interstellar medium along the anomalous spiral arms of NGC 4258 (Lx ~ 1 × 1040, T ~ 0.4 keV) and by interstellar medium escaping from NGC 4258 disk into the approaching halo hemisphere (Lx ~ 4 × 1039 erg s−1, T ~ 0.2 keV)Surface brightness, temperature and absorption profiles have been taken for the X-rays in the regions of the anomalous arms. The highest and lowest absorption was received for the NW and SE tips of the arms, respectively. Our X-ray findings are compared to a model of the anomalous arms which suggests that the bar of the galaxy causes shocks in the interstellar medium and might heat a small part of it to X-ray temperatures.

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The Diffuse Interstellar Bands: an Elderly Astro-Puzzle Rejuvenated

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311024951 ◽

2011 ◽

Vol 7 (S280) ◽

pp. 162-176 ◽

Cited By ~ 3

Author(s):

Nick L. J. Cox

Keyword(s):

Interstellar Medium ◽

Organic Compounds ◽

Recent Progress ◽

Organic Molecules ◽

Exact Nature ◽

Diffuse Band ◽

Small Organic Molecules ◽

Complex Component ◽

Diffuse Interstellar Bands ◽

The Universe

AbstractThe interstellar medium constitutes a physically and chemically complex component of galaxies and is important in the cycle of matter and the evolution of stars. From various spectroscopic clues we now know that the interstellar medium is rich in organic compounds. However, identifying the exact nature of all these components remains a challenge. In particular the identification of the so-called diffuse band carriers has been alluding astronomers for almost a century.In recent decades, observational, experimental and theoretical advances have rapidly lead to renewed interest in the diffuse interstellar bands (DIBs). This has been instigated partly by their perceived relation to the infrared aromatic emission bands, the UV extinction bump and far-UV rise, and the growing number of (small) organic molecules identified in space.This chapter gives an overview of the observational properties and behaviour of the DIBs, and their presence throughout the Universe. I will highlight recent progress in identifying their carriers and discuss their potential as tracers and probes of (extra)-Galactic ISM conditions.

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Abundances in the Gaseous Galactic Halo

Highlights of Astronomy ◽

10.1017/s1539299600020049 ◽

1998 ◽

Vol 11 (1) ◽

pp. 86-89

Author(s):

Ulysses J. Sofia

Keyword(s):

Interstellar Medium ◽

Gas Phase ◽

High Velocity ◽

Galactic Halo ◽

Solar Neighborhood ◽

Local Interstellar Medium ◽

The Galaxy ◽

Metal Abundances ◽

High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

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Astrophysical MHD turbulence: confluence of observations, simulations, and theory

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313002718 ◽

2012 ◽

Vol 8 (S294) ◽

pp. 325-336 ◽

Cited By ~ 1

Author(s):

Blakesley Burkhart ◽

Alex Lazarian

Keyword(s):

Star Formation ◽

Interstellar Medium ◽

Magnetic Reconnection ◽

Particle Transport ◽

Recent Progress ◽

Critical Component ◽

Dynamo Theory ◽

Mhd Turbulence ◽

The Galaxy

AbstractMagnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

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DIBs, Interstellar Dust, and Extinction

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313015780 ◽

2013 ◽

Vol 9 (S297) ◽

pp. 147-152 ◽

Cited By ~ 1

Author(s):

G. C. Clayton

Keyword(s):

Interstellar Medium ◽

Interstellar Dust ◽

Dust Grains ◽

Weak Correlation ◽

Interstellar Clouds ◽

The Galaxy ◽

The Relationship

AbstractThe relationship between DIBs and dust is still unknown. The correlation between reddening and DIB strength means that the DIBs are mixed in with the dust and gas in interstellar clouds. The DIBs are relatively stronger in the diffuse interstellar medium than in dense clouds. There is only a weak correlation between the DIBs and the UV extinction parameters including the 2175 Å bump strength and the far-UV rise. In addition, the bump dust grains are sometimes polarized, while the DIBs are not. However, observations of DIBs in the SMC show that when the 2175 Å bump is weak or missing so are the DIBs. Two of the four sightlines that deviate strongly from the CCM UV extinction in the Galaxy show weak DIBs.

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The Unidentified Infrared Bands in the Diffuse Interstellar Medium across the Galaxy Based on theInfrared Telescope in SpaceMid‐Infrared Spectrometer Observation

The Astrophysical Journal ◽

10.1086/420919 ◽

2004 ◽

Vol 609 (1) ◽

pp. 203-219 ◽

Cited By ~ 39

Author(s):

Itsuki Sakon ◽

Takashi Onaka ◽

Daisuke Ishihara ◽

Takafumi Ootsubo ◽

Issei Yamamura ◽

...

Keyword(s):

Interstellar Medium ◽

The Galaxy ◽

Infrared Spectrometer

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Analysis of the Interstellar Medium Properties of the Herschel Reference Survey Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313001385 ◽

2012 ◽

Vol 8 (S292) ◽

pp. 284-284

Author(s):

Laure Ciesla ◽

Keyword(s):

Interstellar Medium ◽

Physical Properties ◽

Radiation Field ◽

Statistical Study ◽

Dust Mass ◽

Multi Wavelength ◽

Nearby Galaxies ◽

Photodissociation Regions ◽

K Band

AbstractThe Herschel Reference Survey is a guaranteed time key project aimed at studying the physical properties of the interstellar medium (ISM) of 323 nearby galaxies, covered by multi-wavelength data. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types and environments. We conduct a statistical study on the ISM properties of nearby galaxies based on the analysis of their SED. To achieve this goal, we fit the data with the models of Draine & Li (2007) to obtain the intensity of interstellar radiation field, the PAH abundance, the contribution of photodissociation regions, and the dust mass.

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Assessing the sources of reionisation: a spectroscopic case study of a 30× lensed galaxy at z ∼ 5 with Lyα, C iv, Mg ii, and [Ne iii]

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2591 ◽

2021 ◽

Author(s):

Joris Witstok ◽

Renske Smit ◽

Roberto Maiolino ◽

Mirko Curti ◽

Nicolas Laporte ◽

...

Keyword(s):

Radiation Field ◽

Gravitational Lensing ◽

Equivalent Width ◽

Line Ratio ◽

Lyman Continuum ◽

Distant Galaxies ◽

Hard Radiation ◽

The Galaxy ◽

Galaxy Population ◽

Gas Accretion

Abstract We present a detailed spectroscopic analysis of a galaxy at z ≃ 4.88 that is, by chance, magnified ∼30 × by gravitational lensing. Only three sources at z ≳ 5 are known with such high magnification. This particular source has been shown to exhibit widespread, high equivalent width ${\rm C\, {\small IV}}\, \lambda \, 1549$ emission, implying it is a unique example of a metal-poor galaxy with a hard radiation field, likely representing the galaxy population responsible for cosmic reionisation. Using UV nebular line ratio diagnostics, VLT/X-shooter observations rule out strong AGN activity, indicating a stellar origin of the hard radiation field instead. We present a new detection of ${[\rm Ne\, {\small III}]}\, \lambda \, 3870$ and use the [Ne iii]/[O ii] line ratio to constrain the ionisation parameter and gas-phase metallicity. Closely related to the commonly used [O iii]/[O ii] ratio, our [Ne iii]/[O ii] measurement shows this source is similar to local “Green Pea” galaxies and Lyman-continuum leakers. It furthermore suggests this galaxy is more metal poor than expected from the Fundamental Metallicity Relation, possibly as a consequence of excess gas accretion diluting the metallicity. Finally, we present the highest redshift detection of ${\rm Mg\, {\small II}}\, \lambda \, 2796$, observed at high equivalent width in emission, in contrast to more evolved systems predominantly exhibiting Mg ii absorption. Strong Mg ii emission has been observed in most z ∼ 0 Lyman-continuum leakers known and has recently been proposed as an indirect tracer of escaping ionising radiation. In conclusion, this strongly lensed galaxy, observed just 300 Myr after reionisation ends, enables testing of observational diagnostics proposed to constrain the physical properties of distant galaxies in the JWST/ELT era.

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