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

2. Contents 1.Evidences 2.Why is important to study the properties of dust? 3.General introduction 4.Data presentation 5.Analysis, results & conclusions for 8 translucent regions 6.TMC-2: a dense cloud 7.Dust in shell galaxies

3. Dust evidences … Discovery of dust particles in the IS space (Trumpler 1930) 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) 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 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 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 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 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) It affects estimations of basic properties of distant galaxies (SFR, mass determination)

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

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

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

8. Translucent regions Seminar 14 December 2007 Carlos del Burgo

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

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

11. Analysis approach Convolve C100 images with the C200’s theoretical beam profile and resample according to the same pixel size and grid Convolve C100 images with the C200’s theoretical beam profile and resample according to the same pixel size and grid Optical extinction A V from USNO and 2MASS star counts Optical extinction A V from USNO and 2MASS star counts Colours obtained from pixel-to-pixel correlation diagrams Colours obtained from pixel-to-pixel correlation diagrams Colours Fitting with 1 (unimodal) or 2 (bimodal) straight lines to determine the ratios I /I 200  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 Unimodal and bimodal correlations Unimodal and bimodal correlations Large variation in ratios I 60 /I 200 and I 90 /I 200 Large variation in ratios I 60 /I 200 and I 90 /I 200 Above a given I 200, the ratios are low Above a given I 200, the ratios are low I 60 /I 200 I 90 /I 200 60µm 200µm 90µm del Burgo et al. 2003 Siebenmorgen & Krügel. 1992, A&A 259, 614 VSGs disappear above a certain column density

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

14. BG colour temperatures Assuming β =2, we have derived colour temperatures (T) from I 150 /I 200 both for the regions (from ISO) and local sky background (from COBE) both for the regions (from ISO) and local sky background (from COBE) I 200 Colour temperature versus mean I 200 Warm Cold del Burgo et al. 2003 T changes continuously as a function of column density (as traced by I 200 ) T changes continuously as a function of column density (as traced by I 200 ) There is no indication of a discrete 2 T distribution (Lagache et al. 1998) There is no indication of a discrete 2 T distribution (Lagache et al. 1998)

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

16. Colder regions emit relatively more FIR emission per A V Colder regions emit relatively more FIR emission per A V 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 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 The gradual change in emissivity as a function of T indicates that there is a close relationship between colour temperature and FIR dust properties Far-infrared opacities: implications 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 Evolution of dust grains in dense regions via gas accretion onto grains and the coagulation of grains and the coagulation of grains Particle cluster aggregation Cluster cluster aggregation CORE UV radiation field produces complex molecules (e.g. CH 3 OH) in the envelope of the dust grains CO H20H20H20H20 NH 3 H 2 CO PAH CH 4 0.1µm Chemistry and dynamics Stognienko et al. 1995

18. Ratios I 60 /I 200, I 90 /I 200 show a large/decreasing variation with I 200. VSGs disappear above a given column density. Ratios I 60 /I 200, I 90 /I 200 show a large/decreasing variation with I 200. VSGs disappear above a given column density. Far-IR colour I 150 /I 200 shows a very tight trend with I 200. BGs have a colour temperature that depends on the column density Far-IR colour I 150 /I 200 shows a very tight trend with I 200. BGs have a colour temperature that depends on the column density Gradual variation of emissivity and opacity relative to A V. Gradual variation of emissivity and opacity relative to A V. At lower temperatures the grains present an enhanced FIR emissivity At lower temperatures the grains present an enhanced FIR emissivity Two component model. Two component model. Cold component: T  13 K, enhanced FIR emissivity  Coagulation Cold component: T  13 K, enhanced FIR emissivity  Coagulation Warm component: BGs with standard T and emissivity Warm component: BGs with standard T and emissivity Conclusions

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

20. Introduction  HC 5 N (J=9-8) and NH 3 observations (Myers et al. 1979): TMC-2 is a small (~0.1 pc in size) dense 1979): TMC-2 is a small (~0.1 pc in size) dense (~4 10 4 cm -3 ) low-mass (1 M  ) nearly round fragment (~4 10 4 cm -3 ) low-mass (1 M  ) nearly round fragment in stable equilibrium in stable equilibrium  TMC-2 is part of B18 dark cloud (Barnard 1928). Observations in HI self absorption (Batrla et al. 1981, Observations in HI self absorption (Batrla et al. 1981, Pöppel et al. 1983), H 2 CO (Pöppel et al. 1983). Pöppel et al. 1983), H 2 CO (Pöppel et al. 1983). Surveys in HI (Hartmann & Burton 1997), CO (J=1-0) Surveys in HI (Hartmann & Burton 1997), CO (J=1-0) (Dame et al. 2001), 13 CO (J=1-0) (Mizuno et al. 1995) (Dame et al. 2001), 13 CO (J=1-0) (Mizuno et al. 1995) and C 18 O (J=1-0) (Onishi et al. 1996) and C 18 O (J=1-0) (Onishi et al. 1996)  2MASS extinction (Padoan et al. 2002)

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

22. HI cold 100 µm 60 µm Warm component   N(HI)/N(H 2 )  5 10 -3 Pöppel et al. 1983 T  20 K A V ~0.2 mag A V ~0.2 mag (using  200 / A V of the DISM)  200 =0.2 10 -4, cold, cold

23. Cold component: T and  200 maps  200 × 10 -4 T [K] del Burgo & Laureijs, 2005 W(C 18 O)[K km s -1 ]+contours of  200 ×10 -4 C 18 O from Onishi et al. 1996, ApJ 465, 815 W( 13 CO)[K km s -1 ]+contours of 100µm,cold

24. del Burgo & Laureijs, 2005 I 200 /A V and  200 /A V

25. Conclusions TMC-2: The warm and cold components are spatially separated TMC-2: The warm and cold components are spatially separated Warm component likely consists of BGs at  20 K and VSGs Warm component likely consists of BGs at  20 K and VSGs Cold component has T=12.5 K and enhanced emissivity Cold component has T=12.5 K and enhanced emissivity  grain coagulation and mantle growth processes  grain coagulation and mantle growth processes Column densities derived from 13 CO (J=1-0) and 2MASS are in agreement Column densities derived from 13 CO (J=1-0) and 2MASS are in agreement Good correlation between W( 13 CO) and I cold (100) Good correlation between W( 13 CO) and I cold (100)  change in the dust properties wrt DISM at n(H 2 )  10 3 cm -3  change in the dust properties wrt DISM at n(H 2 )  10 3 cm -3 W(C 18 O) and  200 correlate very well for TMC-2* and Northern region W(C 18 O) 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. 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: 10 5 -10 7 M  (Temi et al. 2004, 2007) Introduction

28. NGC 5982 (type I shell galaxy) Spitzer IRAC (7’x7’ (galaxy) + 7’x7’ (sky); 1.8” FWHM): a)3.6 µm b)4.5 µm c)5.8 µm d)8.0 µm e)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. 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)= µ e + c n [(r/r n ) 1/n -1] µ (r)= µ e + c n [(r/r n ) 1/n -1] c n =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 Surface photometry: global parameters del Burgo, Carter, Sikkema (2008).

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

31. Shell profiles 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) Metal-poor Younger stellar population Different dust properties Del Burgo et al. 2008

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 10 9 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