DOCSLIB.ORG

Analysis of Interstellar Dust Using Linear Polarization

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Analysis of Interstellar Dust Using Linear Polarization AMERICAN JOURNAL OF SCIENTIFIC AND INDUSTRIAL RESEARCH © 2010, Science Huβ, http://www.scihub.org/AJSIR ISSN: 2153-649X doi:10.5251/ajsir.2010.1.2.180.189 Analysis of interstellar dust using linear polarization Ali Abdul Sattar Jaber AL – Edhari Department of Physics, College of Science, Al- Muthanna University, Iraq E-mail: [email protected] Tel: +964-7811238920 ABSTRACT This paper, presents the study and analysis of the optical properties of interstellar dust grains. Attempt is made to select a suitable model which defines the structure and composition of these grains, by studying the linear polarization features .We shall present the application of the Serkowski law fit of linear polarization models. In this work we shall present and analysis the data for linear polarization of 6 regions HD142250 , HD34078 , HD46202, HD48099, HD147889 and HD154445 . The hollow needle shape cylindrical bacteria can be fit with reasonable agreement to the normalized linear polarization data in infrared to visible region of the spectrum. Serkowski law fit is still the excellent representation of linear polarization of the star lights of all the regions. Keywords: ISM, Galaxy, Interstellar, matter – Polarization, Microbial Model INTRODUCTION is fixed unless polarization is caused by different Observation of differing physical conditions of materials in different directions (Clayton and Mathis, interstellar dust provides valuable information about 1988). the size, shape and composition of the grains. The The wavelength dependence of interstellar linear polarization was first recognized by Serkowski, et al first information concerning the nature of the (1975). They found that interstellar linear polarization interstellar dust grains came from observations of the can be fitted well by an empirical relation ,Figure(1), characteristics on polarization of star lights (Clayton which is now universally accepted and considered and Martin, 1985). as excellent interpretation of normalized linear Polarization produced by non-spherical interstellar polarization of starlight . The polarization of starlight is generally attributed to interstellar dust. It is another aligned grains is also widely observed in the lines of important feature attributed to the scattering sight to (OB) stars over a similar spectral range properties of the dust. The linear and circular (Clayton and Martin, 1983). polarization of star light was accidentally discovered Linear polarizations are integrals over the same over fifty years ago. It is well established that particle size distributions for the aligned grains. The interstellar polarization is produced by non spherical integrands involve the product of the particle size interstellar dust grains aligned by Galactic magnetic distributions times the appropriate cross sections for field. polarization. The cross sections are determined by the material and geometry of the grain. So their ratio 1.0 0.8 0.6 0.4 0.2 0.0 0.00.51.01.52.02.53.03.54.04.5 Fig 1: Normalized Serkowski Linear Polarization Curve ,λmax=0.55µm , k=0.923 Am. J. Sci. Ind. Res., 2010, 1(2): 180-189 Linear Polarization: Sometimes the light received polarization was first recognizes by Serkowski et.al from celestial objects is polarized. This polarization (1975). They found that a good fit to this dependence can be detected by placing a polarized filter in front of can be made by using the following empirical relation The detector. The filter only passes radiation whose 2 electric field vector is parallel to the polarization P/Pmax=exp{-K Ln (λmax /λ)} …………..4 direction of the filter. Rotating the filter, different polarizations of the incoming light are passed. If the where Pmax and λma are previously defined and K is incoming light is unpolarized , the amount of light some constant. Although the relation is empirical, it is coming through will not depend on the angle through universally accepted and considered as excellent which the filter has been rotated. If the incoming interpretation of linear polarization and is known as light is completely linearly polarized, there will be one Serkowski law fit (Clayton and Martin, 1983). Clayton position of the filter for which the image can be seen et. al (1992) have found that the linear interstellar at full brightness and another position 90° away, for polarization can be fitted well by modified Serkowski which no image can be seen. If the incoming light is law fit from short far Ultraviolet to long infrared partially polarized, a maximum brightness can be wavelengths. For Galactic stars, it has been found seen at one position and a minimum brightness that K and λma are closely related, the most recent when the filter is rotated by 90°. Greater the amount determination from observations of 105 stars being of polarization, greater the contrast between the maximum and the minimum Kutner (1987). When K = 1.66 λma + 0.01 …………………….5 unpolarized starlight passes through interstellar dust clouds, it can emerge with a slight degree of linear Interstellar linear polarization is now generally polarization. This means that the polarization must be thought to be produced by non spherical dust grains caused by the dust itself Clayton et. al (1992) . If Imax aligned by the Galactic magnetic field ,Several and Imjn are the maximum and minimum intensities models have been put forward that attempt to fit most recorded as the polaroid is rotated , the polarization P or all of the known extinction and polarization is defined Wickramasinghe(1967) by features , but no one model is completely successful. Silicates are presented in all models because the P= [Imax- Imin] / [Imax - Imin] …1 polarization of the l0µm feature is attributed to aligned silicate grains Massa et. al. (1983) .In most o By this definition P=0 if Imax= Imin, i.e. corresponding models the 2175 A extinction bump is produced by to unpolarized light and P=1.0 if Imin =0.0, i.e. small graphite grains (Szomoru and corresponding to total linear polarization. For partial Guhatiiakutta,1999). Recent studies have shown that plane polarization, P lies between zero and one .It the wavelength dependence of the extinction and can be shown that the linear polarization is related to polarization Bradely et. al. (1999) is in the red and the differences in optical depths ( ∆τ ) for light with infrared may be the same from one line of sight to electric vector in two perpendicular directions by the another. The observed variations seem to be relation confined to the blue and Ultraviolet wavelength ∆τ = 2P ….……..2 ranges. Observations of the wavelength dependence of interstellar polarization in the Ultraviolet and its or expressed in magnitudes , using equation: behavior across the 2175°A feature can play an A=1.086τ , we have important role .in distinguishing among the Amp = 2.172P …3 completing models for interstellar dust. where Amp denotes the differences of polarization . The wavelength dependence of interstellar linear 181 Am. J. Sci. Ind. Res., 2010, 1(2): 180-189 Observation and Astrometry data 1- HD 142250: Constellation: Scorpius Right ascension: 15h54m30.00s Declination: -27°20'19.0" Apparent magnitude: 6.14 Distance: 162.866 parsecs Proper motion RA: -14 Proper motion Dec: -26.3 B-T magnitude: 6.056 V-T magnitude: 6.128 2- HD 34078: Constellation: Auriga Right ascension: 05h16m18.20s Declination: +34°18'43.0" Apparent 5.96 magnitude: Distance: 446.429 parsecs Proper motion RA: -4.3 Proper motion Dec: 44 B-T magnitude: 6.237 V-T magnitude: 6.025 182 Am. J. Sci. Ind. Res., 2010, 1(2): 180-189 3- HD 46202: Constellation: Monoceros Right ascension: 06h32m10.47s Declination: +04°57'59.8" Apparent magnitude: 8.271 Proper motion RA: -3.3 Proper motion Dec: 1.4 B-T magnitude: 8.354 V-T magnitude: 8.278 4- HD 48099: Constellation: Monoceros Right ascension: 06h41m59.30s Declination: +06°20'42.0" Apparent magnitude: 6.37 Distance: 10000000 parsecs Proper motion RA: 1.6 Proper motion Dec: 3.8 B-T magnitude: 6.254 V-T magnitude: 6.341 183 Am. J. Sci. Ind. Res., 2010, 1(2): 180-189 5- HD 147889: Constellation: Ophiucus Right ascension: 16h25m24.32s Declination: -24°27'56.6" Apparent magnitude: 7.957 Distance: 135.87 parsecs Proper motion RA: -1.4 Proper motion Dec: -25 B-T magnitude: 8.877 V-T magnitude: 8.033 6- HD 154445: Constellation: Ophiucus Right ascension: 17h05m32.30s Declination: -00°53'31.0" Apparent magnitude: 5.64 Distance: 234.742 parsecs Proper motion RA: 4 Proper motion Dec: -2 B-T magnitude: 5.753 V-T magnitude: 5.648 Table 1: Polarization characteristics of 6 individual stars HD P K P A . 0 max 197770 3.81 0.857 131.1 37903 2.04 1.139 120.6 2905 1.53 0.89 86.1 25443 5.17 0.823 137.1 161056 4.03 0.989 68.4 7252 3.49 0.873 95.2 184 Am. J. Sci. Ind. Res., 2010, 1(2): 180-189 RESULT AND DISCUSSION while the imaginary parts of the bacterial refractive Interstellar grains cause a partial linear polarization of indices are k= 0.025, 0.04, 0.03, 0.008, 0.02, 0.02 for star light because components of them are aligned the stars in figure (3) to (8) in sequence. with regard to the magnetic field of the galaxy. The The modified Serkowski law fit, equation (4), with the existence of polarization of star lights requires a values of K, equation (5) for value Pmax and λmax degree of anisotropy in the aligned dust grains. The tabulated in table (1). It can be seen that the current understanding of alignment requires Serkowski relation and hollow cylindrical bacteria polarization to be produced by aligned, non spherical model are in good agreement with the observed dust grains. polarization data .The fitting of the models in the UV Historically, the use of the infinite cylinder has region are not good .
Load more

Recommended publications
  • The Co-Existence of Hot and Cold Gas in Debris Discs? I
    A&A 614, A3 (2018) https://doi.org/10.1051/0004-6361/201732329 Astronomy & © ESO 2018 Astrophysics The co-existence of hot and cold gas in debris discs? I. Rebollido1, C. Eiroa1, B. Montesinos2, J. Maldonado3, E. Villaver1, O. Absil4, A. Bayo5,6, H. Canovas1,7, A. Carmona8, Ch. Chen9, S. Ertel10, A. Garufi1, Th. Henning11, D. P. Iglesias5,6, R. Launhardt11, R. Liseau12, G. Meeus1, A. Moór13, A. Mora14, J. Olofsson5,6, G. Rauw4, and P. Riviere-Marichalar15 1 Departamento. Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain e-mail: [email protected] 2 Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, Villanueva de la Cañada, 28692 Madrid, Spain 3 INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy 4 STAR Institute, Université de Liège, F.R.S.-FNRS, 19c Allée du Six Août, 4000 Liège, Belgium 5 Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Casilla, 5030 Valparaíso, Chile 6 Núcleo Milenio de Formación Planetaria-NPF, Universidad de Valparaíso, Av. Gran Bretaña, 1111 Valparaíso, Chile 7 European Space Astronomy Centre (ESA), PO Box 78, Villanueva de la Cañada, 28691 Madrid, Spain 8 Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France 9 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21212, USA 10 Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA 11 Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany 12 Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden 13 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, PO Box 67, 1525 Budapest, Hungary 14 Aurora Technology B.V.
    [Show full text]
  • The Co-Existence of Hot and Cold Gas in Debris Discs
    The co-existence of hot and cold gas in debris discs Downloaded from: https://research.chalmers.se, 2021-09-25 13:51 UTC Citation for the original published paper (version of record): Rebollido, I., Eiroa, C., Montesinos, B. et al (2018) The co-existence of hot and cold gas in debris discs Astronomy and Astrophysics, 614 http://dx.doi.org/10.1051/0004-6361/201732329 N.B. When citing this work, cite the original published paper. research.chalmers.se offers the possibility of retrieving research publications produced at Chalmers University of Technology. It covers all kind of research output: articles, dissertations, conference papers, reports etc. since 2004. research.chalmers.se is administrated and maintained by Chalmers Library (article starts on next page) A&A 614, A3 (2018) https://doi.org/10.1051/0004-6361/201732329 Astronomy & © ESO 2018 Astrophysics The co-existence of hot and cold gas in debris discs? I. Rebollido1, C. Eiroa1, B. Montesinos2, J. Maldonado3, E. Villaver1, O. Absil4, A. Bayo5,6, H. Canovas1,7, A. Carmona8, Ch. Chen9, S. Ertel10, A. Garufi1, Th. Henning11, D. P. Iglesias5,6, R. Launhardt11, R. Liseau12, G. Meeus1, A. Moór13, A. Mora14, J. Olofsson5,6, G. Rauw4, and P. Riviere-Marichalar15 1 Departamento. Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain e-mail: [email protected] 2 Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, Villanueva de la Cañada, 28692 Madrid, Spain 3 INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy 4 STAR Institute, Université de Liège, F.R.S.-FNRS, 19c Allée du Six Août, 4000 Liège, Belgium 5 Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Casilla, 5030 Valparaíso, Chile 6 Núcleo Milenio de Formación Planetaria-NPF, Universidad de Valparaíso, Av.
    [Show full text]
  • Diffuse Interstellar Bands in Upper Scorpius: Probing Variations in the DIB Spectrum Due to Changing Environmental Conditions
    UvA-DARE (Digital Academic Repository) Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions Vos, D.A.I.; Cox, N.L.J.; Kaper, L.; Spaans, M.; Ehrenfreund, P. DOI 10.1051/0004-6361/200809746 Publication date 2011 Document Version Final published version Published in Astronomy & Astrophysics Link to publication Citation for published version (APA): Vos, D. A. I., Cox, N. L. J., Kaper, L., Spaans, M., & Ehrenfreund, P. (2011). Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions. Astronomy & Astrophysics, 533. https://doi.org/10.1051/0004- 6361/200809746 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:01 Oct 2021 A&A 533, A129 (2011) Astronomy DOI: 10.1051/0004-6361/200809746 & c ESO 2011 Astrophysics Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions, D.
    [Show full text]
  • The Co-Existence of Hot and Cold Gas in Debris Discs I
    Astronomy & Astrophysics manuscript no. 32329_corrected_arxiv c ESO 2018 January 25, 2018 The co-existence of hot and cold gas in debris discs I. Rebollido1, C. Eiroa1, B. Montesinos2, J. Maldonado3, E. Villaver1, O. Absil4, A. Bayo5; 6, H. Canovas1; 7, A. Carmona8, Ch. Chen9, S. Ertel10, A. Garufi1, Th. Henning11, D. P. Iglesias5; 6, R. Launhardt11, R. Liseau12, G. Meeus1, A. Moór13, A. Mora14, J. Olofsson5; 6, G. Rauw4, and P. Riviere-Marichalar15 1 Dpto. Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain, e-mail: [email protected] 2 Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo, s/n, 28692 Villanueva de la Cañada, Madrid, Spain 3 INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy 4 STAR Institute, Université de Liège, F.R.S.-FNRS, 19c Allée du Six Août, B-4000 Liège, Belgium 5 Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, 5030 Casilla, Valparaíso, Chile 6 Núcleo Milenio de Formación Planetaria - NPF, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile 7 European Space Astronomy Centre (ESA), PO Box, 78, 28691 Villanueva de la Cañada, Madrid, Spain 8 Université de Toulouse, UPS-OMP, IRAP, Toulouse F-31400, France 9 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21212, USA 10 Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA 11 Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, D-69117 Heidelberg, Germany 12 Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala, Sweden 13 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, PO Box 67, 1525 Budapest, Hungary 14 Aurora Technology B.V.
    [Show full text]
  • July 2017 BRAS Newsletter
    July 2017 Issue th Next Meeting: Saturday, July 15 , 11 a.m., at LIGO (This special meeting will NOT be held at the usual time and place.) PROGRAM: BRAS Potluck and LIGO Tour (Laser Interferometer Gravitational-Wave Observatory) 19100 LIGO Lane, Livingston, LA 70754 https://www.ligo.caltech.edu/LA What's In This Issue? President’s Message Secretary's Summary Outreach Report - FAE Event Photos Light Pollution Committee Report Recent Forum Entries 20/20 Vision Campaign Messages from the HRPO Perseid Meteor Shower Partial Solar Eclipse Observing Notes – Scorpius –The Scorpion & Mythology Like this newsletter? See past issues back to 2009 at http://brastro.org/newsletters.html Newsletter of the Baton Rouge Astronomical Society July 2017 President’s Message July is here, half the year is gone. This month’s meeting will be at LIGO in Livingston on July 15th, along with the pot luck picnic, gates will open to BRAS members and family members at 11:00 a.m. After the picnic and a short meeting, we will assist LIGO on their public day along with solar viewing. If you and yours have not been to LIGO, you are in for a treat! Open to the public from 1 to 5 p.m. We will sell a few more tickets for the Meade telescope, and then announce the winner! Last month’s riddle winners, Scott Cadwallader, Bart Bennet, and Roz Readinger will get their free raffle tickets for being the first 3 to send me the answer to last month’s question, if they show up at the picnic.
    [Show full text]
  • High S/N Echelle Spectroscopy in Young Stellar Groups II. Rotational
    A&A manuscript no. (will be inserted by hand later) ASTRONOMY AND Your thesaurus codes are: ASTROPHYSICS 08.05.1; 08.06.2; 08.18.1; 10.15.2 Sco OB2 20.3.2018 High S/N Echelle Spectroscopy in Young Stellar Groups ⋆ II. Rotational Velocities of Early-Type Stars in Sco OB2 A.G.A. Brown@1, W. Verschueren@2,1 @1 Sterrewacht Leiden, P.O. Box 9513, 2300 RA, Leiden, The Netherlands @2 University of Antwerp (RUCA), Astrophysics Research Group, Groenenborgerlaan 171, 2020 Antwerpen, Belgium Received... , accepted... Abstract. We investigate the rotational velocities of 1. Introduction early-type stars in the Sco OB2 association. We measure vsini for 156 established and probable members of the An outstanding problem in theories of star formation association. The measurements are performed with three is the so-called angular momentum problem. Molecular different techniques, which are in increasing order of ex- clouds and cloud cores, even if they spin about their axis pected vsini: 1) converting the widths of spectral lines di- only once per Galactic rotation, contain much more an- rectly to vsini, 2) comparing artificially broadened spectra gular momentum than the stars that form from them (see of low vsini stars to the target spectrum, 3) comparing the e.g., Spitzer 1968). Observations suggest that an inter- i He λ4026 line profile to theoretical models. The sample is stellar parent cloud must lose at least two to four or- extended with literature data for 47 established members ders of magnitude of angular momentum for a relatively of Sco OB2. Analysis of the vsini distributions shows that wide binary system and a single star, respectively, to be- there are no significant differences between the subgroups come dynamically possible (see Mouschovias 1991).
    [Show full text]
  • Diffuse Interstellar Bands in Upper Scorpius
    Astronomy & Astrophysics manuscript no. aa09746 c ESO 2018 November 7, 2018 Diffuse interstellar bands in Upper Scorpius: Probing variations in the DIB spectrum due to changing environmental conditions⋆ D.A.I. Vos1, N.L.J. Cox2, L. Kaper3, M. Spaans4, and P. Ehrenfreund5 1 Radboud University Nijmegen, Toernooiveld 1, Postbus 9010, 6500 GL, Nijmegen, The Netherlands 2 Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200D, bus 2401, 3001, Leuven, Belgium 3 Astronomical Institute ”Anton Pannekoek”, Universiteit van Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands 4 Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Postbus 800, 9700 AV Groningen, The Netherlands 5 Astrobiology Group, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands Received 7 March 2008; Accepted 28 July 2011 ABSTRACT Aims. We study the effects of local environmental conditions affecting the diffuse interstellar band (DIB) carriers within the Upper Scorpius subgroup of the Sco OB2 association. The aim is to reveal how the still unidentified DIB carriers respond to different physical conditions prevailing in interstellar clouds, in order to shed light on the origin of the DIB carriers. Methods. We obtained optical spectra with FEROS on the ESO 1.52m telescope at La Silla, Chile, and measured the equivalent widths of five DIBs (at 5780, 5797, 6196, 6379, and 6613 Å) as well as those of absorption lines of di-atomic molecules (CH, CH+, CN) and atoms (K i, Ca i) towards 89 targets in the direction of Upper Scorpius. We construct a simple radiative transfer and chemical network model of the diffuse interstellar medium (ISM) sheet in front of Upp Sco to infer the effective radiation field.
    [Show full text]
  • Appendix A: Orbital Elements
    Appendix A: Orbital Elements Many of the items in this Appendix have been explained elsewhere in the text, but, for clarity, they have been drawn together into this one section. The size and shape of a satellite’s orbit is determined by its speed and mass, and also by the mass of the object it is orbiting. The size, shape and orientation of an orbit can be described by six orbital elements or orbital parameters, known as Keplerian ele- ments or element sets. Different sets of elements can be used for different purposes. The terms used sound complicated, but taken individually each is relatively simple. These explanations have been taken with reference to an Earth-orbiting satellite, however, they can easily be adapted for satellites orbiting other celestial bodies. If all of the elements are known, the exact location of a satellite can be calculated. The Keplerian elements are: Inclination (i) Longitude of the ascending node (W) Argument of periapsis (w) Eccentricity (e) Semi-major axis (a) Anomaly at epoch (v) Time of periapsis or perigee passage (T) may be used instead of the Anomaly at epoch (v) Inclination (i) A satellite will always travel around the centre of the body it is orbiting and therefore it will always cross the equator twice in every orbit, unless, of course, it orbits directly above the equator. It will cut it as it travels from the southern hemisphere to the northern and again when it crosses from the northern to the southern hemi- sphere. The angle it makes when it crosses the equator from the 303 304 It’s ONLY Rocket Science southern hemisphere to the northern hemisphere is called the inclination, and this defines the orientation of the orbit with respect to the equator.
    [Show full text]
  • Diffuse Interstellar Bands in Upper Scorpius: Probing Variations in the DIB Spectrum Due to Changing Environmental Conditions,
    A&A 533, A129 (2011) Astronomy DOI: 10.1051/0004-6361/200809746 & c ESO 2011 Astrophysics Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions, D. A. I. Vos1,N.L.J.Cox2,L.Kaper3, M. Spaans4, and P. Ehrenfreund5 1 Radboud University Nijmegen, Toernooiveld 1, Postbus 9010, 6500 GL Nijmegen, The Netherlands e-mail: [email protected] 2 Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, bus 2401, 3001 Leuven, Belgium 3 Astronomical Institute “Anton Pannekoek”, Universiteit van Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands 4 Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Postbus 800, 9700 AV Groningen, The Netherlands 5 Astrobiology Group, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands Received 7 March 2008 / Accepted 28 July 2011 ABSTRACT Aims. We study the effects of local environmental conditions affecting the diffuse interstellar band (DIB) carriers within the Upper Scorpius subgroup of the Sco OB2 association. The aim is to reveal how the still unidentified DIB carriers respond to different physical conditions prevailing in interstellar clouds, in order to shed light on the origin of the DIB carriers. Methods. We obtained optical spectra with FEROS on the ESO 1.52 m telescope at La Silla, Chile, and measured the equivalent widths of five DIBs (at 5780, 5797, 6196, 6379, and 6613 Å) as well as those of absorption lines of di-atomic molecules (CH, CH+,CN)and atoms (K i,Cai) towards 89 targets in the direction of Upper Scorpius. We construct a simple radiative transfer and chemical network model of the diffuse interstellar medium (ISM) sheet in front of Upp Sco to infer the effective radiation field.
    [Show full text]