scholarly journals Galactic extinction laws: II. Hidden in plain sight, a new interstellar absorption band at 7700 Å broader than any known DIB

2020 ◽  
Author(s):  
J Maíz Apellániz ◽  
R H Barbá ◽  
J A Caballero ◽  
R C Bohlin ◽  
C Fariña
Keyword(s):  
Absorption Band ◽  
General Model ◽  
Molecular Clouds ◽  
Red Giants ◽  
Optical Range ◽  
Interstellar Absorption ◽  
Ob Stars ◽  
Diffuse Interstellar Bands ◽  
The Relationship ◽  
Intermediate Density

Abstract We have detected a broad interstellar absorption band centred close to 7700 Å and with a FWHM of 176.6±3.9 Å. This is the first such absorption band detected in the optical range and is significantly wider than the numerous diffuse interstellar bands (DIBs). It remained undiscovered until now because it is partially hidden behind the A telluric band produced by O2. The band was discovered using STIS@HST spectra and later detected in a large sample of stars of diverse type (OB stars, BA supergiants, red giants) using further STIS and ground-based spectroscopy. The EW of the band is measured and compared with our extinction and K i λλ7667.021,7701.093 measurements for the same sample. The carrier is ubiquitous in the diffuse and translucent Galactic ISM but is depleted in the environment around OB stars. In particular, it appears to be absent or nearly so in sightlines rich in molecular carbon. This behaviour is similar to that of the σ-type DIBs, which originate in the low/intermediate-density UV-exposed ISM but are depleted in the high-density UV-shielded molecular clouds. We also present an update on our previous work on the relationship between E(4405 − 5495) and R5495 and incorporate our results into a general model of the ISM.

Ultrafine Structure in the λ5797 Diffuse Interstellar Absorption Band

1998 ◽  
Vol 495 (2) ◽  
pp. 941-945 ◽  
Author(s):  
T. H. Kerr ◽  
R. E. Hibbins ◽  
S. J. Fossey ◽  
J. R. Miles ◽  
P. J. Sarre
Keyword(s):  
Absorption Band ◽  
Interstellar Absorption ◽  
Ultrafine Structure

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals CO observations of the 30-Doradus region using SEST

1991 ◽  
Vol 148 ◽  
pp. 157-159
Author(s):  
R. S. Booth ◽  
L.E.B. Johansson
Keyword(s):  
Molecular Clouds ◽  
Small Areas ◽  
The Relationship ◽  
Co Observations ◽  
30 Doradus

Using the Swedish-ESO Submillimetre Telescope, we have mapped the CO (1-0) emission in two small areas of the LMC near 30 Dor. Some 20 molecular clouds have been identified and analysed. Cloud masses are calculated assuming virial equilibrium and the relationship between mass and CO luminosity is discussed.

scholarly journals Continuum Wavelength Emission from Embedded, Young, and Massive Stellar Objects Beyond 1 μm

1990 ◽  
Vol 139 ◽  
pp. 113-114
Author(s):  
Thomas Henning ◽  
Werner Pfau
Keyword(s):  
Molecular Clouds ◽  
Dust Emission ◽  
Average Energy ◽  
Hii Regions ◽  
Point Sources ◽  
Color Temperature ◽  
Stellar Objects ◽  
Ob Stars ◽  
Infrared Background ◽  
Wavelength Emission

One of the components of the galactic infrared background (GIRB) radiation is emission by warm dust grains heated by OB stars embedded in molecular clouds. The main contributors are compact HII regions and comparatively radioquiet infrared (IR) point sources such as the Becklin-Neugebauer object. We present the average energy distribution between 1 and 1300 μm for a sample of BN-type objects. The average color temperature between 60 and 100 μm is ~40 K, which is very similar to the color temperature of the observed warm galactic dust emission (WGDE).

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion nebula cluster

2010 ◽  
Vol 6 (S272) ◽  
pp. 208-209 ◽  
Author(s):  
Véronique Petit ◽  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
Laurent Drissen ◽  
Thierry Montmerle ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Theoretical Models ◽  
Magnetic Star ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
The Impact ◽  
The Relationship

AbstractIn some massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind. Although theoretical models and MHD simulations are able to illustrate the dynamics of such a magnetized wind, the impact of this wind-field interaction on the observable properties of a magnetic star - X-ray emission, photometric and spectral variability - is still unclear. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars, by providing empirical observations and confronting theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

Streaming motions of molecular clouds, ionized hydrogen, and OB stars in the Cygnus arm

2001 ◽  
Vol 45 (1) ◽  
pp. 34-43
Author(s):  
T. G. Sitnik ◽  
A. M. Mel’nik ◽  
V. V. Pravdikova
Keyword(s):  
Molecular Clouds ◽  
Ob Stars

scholarly journals Search for CO in Atomic Hydrogen Clouds

1980 ◽  
Vol 87 ◽  
pp. 189-190
Author(s):  
I. Kazès ◽  
J. Crovisier
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Molecular Line ◽  
Preliminary Results ◽  
Comprehensive Search ◽  
Diffuse Clouds ◽  
The Relationship ◽  
Absorption Features

The relationship between dense molecular clouds and diffuse clouds, as well as the mechanisms connected with the formation of molecules in diffuse clouds, may be studied using HI 21-cm line observations and molecular line observations in the same directions. For this purpose we previously studied the OH 18-cm main lines (Kazès et al., 1977) and the 2.6-mm CO lines (Crovisier and Kazès, 1977) in directions where strong 21-cm absorption features had been detected in the Nancay survey (Crovisier et al., 1978). Liszt and Burton (1979) also measured CO lines toward 19 directions observed in the Arecibo 21-cm emission/absorption survey (Dickey et al., 1978). This paper presents preliminary results of a more comprehensive search for 12CO in directions previously studied in the Nancay survey.

scholarly journals Diffuse Interstellar Bands in M33

2013 ◽  
Vol 9 (S297) ◽  
pp. 74-78
Author(s):  
K. T. Smith ◽  
M. A. Cordiner ◽  
C. J. Evans ◽  
N. L. J. Cox ◽  
P. J. Sarre
Keyword(s):  
Equivalent Width ◽  
Milky Way ◽  
Line Of Sight ◽  
Nearby Galaxy ◽  
Diffuse Interstellar Bands ◽  
Upper Limits ◽  
Interstellar Media ◽  
The Relationship

AbstractWe present the first sample of diffuse interstellar bands (DIBs) in the nearby galaxy M33. Studying DIBs in other galaxies allows the behaviour of the carriers to be examined under interstellar conditions which can be quite different from those of the Milky Way, and to determine which DIB properties can be used as reliable probes of extragalactic interstellar media. Multi-object spectroscopy of 43 stars in M33 has been performed using Keck/DEIMOS. The stellar spectral types were determined and combined with literature photometry to determine the M33 reddenings E(B-V)M33. Equivalent widths or upper limits have been measured for the λ5780 DIB towards each star. DIBs were detected towards 20 stars, demonstrating that their carriers are abundant in M33. The relationship with reddening is found to be at the upper end of the range observed in the Milky Way. The line of sight towards one star has an unusually strong ratio of DIB equivalent width to E(B-V)M33, and a total of seven DIBs were detected towards this star.

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