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From diffuse to dense regions

From diffuse to dense regions. The far-infrared signature of dust in high latitude regions. Carlos del Burgo D íaz School of Cosmic Physics Dublin Institute for Advanced Studies. Seminar 14 December 2007 La Laguna. Contents.

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From diffuse to dense regions

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  1. From diffuse to dense regions The far-infrared signature of dust in high latitude regions Carlos del Burgo Díaz School of Cosmic Physics Dublin Institute for Advanced Studies Seminar 14 December 2007 La Laguna

  2. Contents • Evidences • Why is important to study the properties of dust? • General introduction • Data presentation • Analysis, results & conclusions for 8 translucent regions • TMC-2: a dense cloud • Dust in shell galaxies

  3. Dust evidences … • Discovery of dust particles in the IS space (Trumpler 1930) • Dust properties have been inferred mainly by indirect observations till few years ago (see reviews Draine 2003, Whittet 2003) • Direct observations: emission from ZL at ~25 m, dust trails of comets, circumstellar disks of evolved stars, ISM, IR and ULIRGs, AGNs, CFIRB, active star formation at high-redshift

  4. Why is it important to study the dust properties? • Dust and gas (1:100 mass relation) are the components of the ISM. Dust contains ~50% of the heavy metals synthesized by stars • It plays a key role in many astrophysical environments: thermodynamics and chemistry of gas, dynamics of star formation, … • It shapes the SED of many cosmic sources (e.g., galaxies). Absorption and scattering of stellar light and re-emission in the IR and submm • It affects estimations of basic properties of distant galaxies (SFR, mass determination)

  5. Galactic dust emission COBE/DIRBE Surface brightness at 100 m Cirrus: thermal emission from interstellar dust heated by stars in the Milky Way in the solar system and emitted by dust Zodiacal light is scattered de Oliveira-Costa 1999 MJy/sr

  6. Introduction From all-sky map, 1o beam (DIRBE, Lagache et al. 1998) Polycyclic Aromatic Hydrocarbon Sizes: 0.4-1.2 nm PAH Carbon dominated 1.2-15 nm VSG Silicates + dark refractory mantle 15-110 nm BG • The mid- and far-IR emission of IS dust is due to likely PAHs, VSGsandBGs (Desert et al. 1990; Siebenmorgen & Krügel 1992 Weingartner & Draine 2001) • IR colours are used to study: - variations ofLSRF (Laureijs et al. 1986; Bernard et al. 1992) - relativeabundances (Boulanger et al. 1990; Lagache et al. 1998) cold warm Draine 2003 Siebenmorgen & Krügel. 1992, A&A 259, 614

  7. Data presentation:high-latitude dust regions • Data archives (COBE, IRAS, ISO, SPITZER, SCUBA)  IR and submillimetric data to study the dust emission Akari has been launched in February 2006 Herschel and Planck will be launched soon Other future missions: SOFIA, ALMA, JWT • We present results for 1 dense and 9translucent regions. 60-200 μm data from the ISO archive to study: - VSG emission, which peaks at  ~ 60 μm- BGs: warm and cold components • We used additional information: - USNO and 2MASS catalogues  extinction from star counts - COBE/DIRBE  ZL in eight translucent clouds - IRAS and molecular observations  LDN 1780 and TMC-2

  8. Translucentregions Seminar 14 December 2007 Carlos del Burgo

  9. High latitude regions: sample description EMISSION maps: LDN 1563 area~175 armin2 • 9 diffuse to moderately dense regions (peaks AV~1-6 mag) and TMC-2 and its surroundings (peak AV~8 mag) • No dominant heating sources • Galactic latitude |b| > 15° • Data sets with 150 and 200 μm filterbands (except for LDN 1563, and TMC-2) area~274 armin2 del Burgo et al. 2003

  10. Sky at Galactic coordinates: observed dust regions 2 2 3 Map courtesy by Richard Powell

  11. Analysis approach • Convolve C100 images with the C200’s theoretical beam profile and resample according to the same pixel size and grid • Optical extinction AV from USNO and 2MASS star counts • Colours obtained from pixel-to-pixel correlation diagrams Colours Fitting with 1 (unimodal) or 2 (bimodal) straight lines to determine the ratios I/I200  spectral energy distribution Fitting 150 and 200µm with a modified blackbody FB(T)  colour temperature del Burgo et al. 2003, MNRAS 346, 403

  12. Results – VSG colours I60/I200 • Unimodal and bimodal correlations • Large variation in ratios I60/I200 and I90/I200 • Above a given I200, the ratios are low VSGs disappear above a certain column density 90µm 200µm I90/I200 60µm Siebenmorgen & Krügel. 1992, A&A 259, 614 del Burgo et al. 2003

  13. Results – BG colours LB (obtained from COBE/DIRBE) All regions We find a unique relationship between 150 μm and 200 μm surface brightness. This is confirmed by the COBE data of Taurus cloud. ZL subtracted from DIRBE data del Burgo et al. 2003

  14. BG colour temperatures Assuming β=2, we have derived colour temperatures (T) from I150/I200 both for the regions (from ISO) and local sky background (from COBE) Colourtemperatureversus mean I200 • T changes continuously as a function of column density (as traced by I200) • There is no indication of a discrete 2 T distribution (Lagache et al. 1998) Warm Cold del Burgo et al. 2003

  15. Far-infrared opacities: BGs =8 Tw=17.5 K Tc=13.5 K X DISM =4 • I200/AV when colour T  • This increase comes out even stronger in 200/AV • For each los there are two BG components: warm and cold grains • Assuming Tw=17.5 KandTc=13.5 K • The colour T depends on the relative contribution of the warm and cold components  X •   enhancement in the emissivity of the cold grains wrt DISM/warm grains =1 100% cold 60% cold 40% warm 100% warm del Burgo et al., 2003

  16. Far-infrared opacities: implications • Colder regions emit relatively more FIR emission per AV • The enhancement in FIR emissivity can be due to the coagulation of dust grains (del Burgo et al. 2003) – also observed by Cambrésy et al. (2001), Stepnik et al. (2003), Kramer et al. (2003) • The gradual change in emissivity as a function of T indicates that there is a close relationship between colour temperature and FIR dust properties Polaris Flare, Cambrésy et al. 2001  = 8  = 4  = 1 DISM

  17. Dust evolution • Evolution of dust grains in dense regions via gas accretion onto grains • and the coagulation of grains Chemistry and dynamics Particle cluster aggregation Cluster cluster aggregation CO H20 CORE NH3 H2CO PAH CH4 0.1µm UV radiation field produces complex molecules (e.g. CH3OH) in the envelope of the dust grains Stognienko et al. 1995

  18. Conclusions • Ratios I60/I200, I90/I200 show a large/decreasing variation with I200. VSGs disappear above a given column density. • Far-IR colour I150/I200 shows a very tight trend with I200. BGs have a colour temperature that depends on the column density • Gradual variation of emissivity and opacity relative to AV. At lower temperatures the grains present an enhanced FIR emissivity • Two component model. Cold component: T13 K, enhanced FIR emissivity  Coagulation Warm component: BGs with standard T and emissivity

  19. TMC-2: a dense cloud Seminar 14 December 2007 Carlos del Burgo

  20. Introduction • HC5N (J=9-8) and NH3 observations (Myers et al. 1979): TMC-2 is a small (~0.1 pc in size) dense (~4 104 cm-3) low-mass (1 M) nearly round fragment in stable equilibrium • TMC-2 is part of B18 dark cloud (Barnard 1928). Observations in HI self absorption (Batrla et al. 1981, Pöppel et al. 1983), H2CO (Pöppel et al. 1983). Surveys in HI (Hartmann & Burton 1997), CO (J=1-0) (Dame et al. 2001), 13CO (J=1-0) (Mizuno et al. 1995) and C18O (J=1-0) (Onishi et al. 1996) • 2MASS extinction (Padoan et al. 2002)

  21. 60 µm 100 µm 120 µm 200µm Separation of the cold and warm components: vicinity of TMC-2 100 µm 100 µm warm cold 120 µm 120 µm warm cold Area = 1767 arcmin2 del Burgo & Laureijs, 2005

  22. 60 µm Warm component HI cold , cold 100 µm Pöppel et al. 1983 N(HI)/N(H2)5 10-3  T  20 K AV~0.2 mag (using 200/ AV of the DISM)  200=0.2 10-4

  23. Cold component: T and 200 maps W(13CO)[K km s-1]+contours of 100µm,cold W(C18O)[K km s-1]+contours of 200×10-4 200 × 10-4 T [K] del Burgo & Laureijs, 2005 C18O from Onishi et al. 1996, ApJ 465, 815

  24. I200/AV and200/AV del Burgo & Laureijs, 2005

  25. Conclusions • TMC-2:The warm and cold components are spatially separated • Warm component likely consists of BGs at 20 K and VSGs • Cold component has T=12.5 K and enhanced emissivity  grain coagulation and mantle growth processes • Column densities derived from 13CO(J=1-0) and 2MASS are in agreement • Good correlation between W(13CO) and Icold(100) change in the dust properties wrt DISM at n(H2)  103 cm-3 • W(C18O) and 200 correlate very well for TMC-2* and Northern region

  26. Dust distribution in the shell elliptical NGC 5982 Seminar 14 December 2007 Carlos del Burgo

  27. Introduction Shell galaxies (Malin & Carter 1980, 1983) are elliptical galaxies with faint, sharp edged features in their envelopes, generally interpreted as the remnants of mergers of low mass, low velocity dispersion galaxies with the elliptical (Quinn 1984, Hernquist & Quinn 1988) ISM in shell ellipticals: mostly X-ray emitting gas, some warm and cold gas and dust; ~70 % with HI gas (Morganti et al. 2006); ~70 % with warm gas (Sarzi et al. 2006); ~28 % with CO gas (Combes et al. 2007); bulk of dust traced by FIR: 105-107 M (Temi et al. 2004, 2007)

  28. NGC 5982 (type I shell galaxy) • Spitzer • IRAC (7’x7’ (galaxy) + 7’x7’ (sky); • 1.8” FWHM): • 3.6 µm • 4.5 µm • 5.8 µm • 8.0 µm • 8.0 µm excess • MIPS (similar field) • f) 24 µm (6” FWHM) • g) 70 µm (18” FWHM) • h) 160 µm (40” FWHM) • HST (3.37’x3.37’) • V- and I-bands (Sikkema et al. 2007) Del Burgo et al. 2008

  29. Surface photometry: global parameters SB calibration similar to Pahre et al. (2004), but using also aperture corrections of Reach et al. 2005 ELLIPSE and ELLIPFIT to measure the flux and ellipse properties Sérsic profile (1968): µ (r)= µe + cn [(r/rn)1/n-1] cn=f(n) (Caon et al. 1993) Excess emission A scaled stellar photosphere emission template is subtracted from the 4.5, 5.8 and 8 µm emission maps . del Burgo, Carter, Sikkema (2008)

  30. Shells 3.6 µm R-band Del Burgo et al. 2008

  31. Shell profiles Metal-poor Younger stellar population Different dust properties Del Burgo et al. 2008 Shells are bluer than the underlying galaxy: V-I=1.16±0.10 mag (shell), 1.25 mag (underlying galaxy) [3.6]-[4.5]=-0.13 ±0.01 mag, -0.08 mag (underlying galaxy)

  32. Results and interpretation Shells are clearly detected from their stellar emission at 3.6 and 4.5 µm. V-I and [3.6]-[4.5] colours bluer than underlying galaxy. Two new external shells  estimated dynamical age ~1.1 109 years Excess emission possibly trace dust originated by stellar mass loss 24 µm and 3.6 µm are very similar: circumstellar origin Warm and cold dust traced by 70 and 160 µm: mass of 105 M and irregular distributions, not coincident with Eastern HI cloud but consistent in mass (Morganti et al. 2006), not coincident with warm gas (Sarzi et al. 2006). + Presence of KDC. All this supports a merger scenario in NGC 5982

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