the Solar Neighborhood

Transcription

1 Click to edit Master title style Star Formation at High A V in the Solar Neighborhood Amanda Heiderman NSF Fellow UVa/NRAO (w/ Neal Evans, UT Austin) Filaments 2014, October, 11, /13/2014 1

2 Click to edit Master title style Star Formation at High A V in the Solar Neighborhood Amanda Heiderman NSF Fellow UVa/NRAO (w/ Neal Evans, UT Austin) HST+ HI Filaments 2014, October, 11, /13/2014 2

3 Star Click Formation to edit Master in the local title 0.5 style kpc Sun Local 0.5 kpc 500 pc = 1 kpc 1 kpc 1 kpc Cloud Fields R. Benjamin (from Kennicutt & Evans 2012) = 1 kpc 10/13/2014 3

4 Using Nearby ~20 Clouds to Trace low- Click to mass edit Star Master Formation title style Spitzer Legacy Surveys: cores to disks (c2d; Click edit Master text styles Evans+ 2009) Gould s Belt (GB; Dunham+ 2013, Allen+ in prep.) Cloud masses/» Σ gas Fifth from level extinction maps: Σ gas = 15A V (M pc 2 ) 1 kpc Sun 500 pc SFR= N YSO x M YSO / t YSO (M Myr 1 ) from YSO counts, mean mass 0.5 Μ, & lifetimes 1 kpc 1 kpc Cloud Fields 10/13/2014 4

5 All SEDs from Dunham et al. (2013), PPVI review chapter Classes Stages Standard evolutionary scenario Click single to edit isolated Master low-mass title star style Prestellar core Wavelength (μm) igure adapted from McCaughrean, unpublished, by A. Stutz Core collapse? Candidate FHSC? First hydrostatic core Class 0 protostar outflow n~ cm -3 T~10 K n~ cm -3 Protostar with disk T~ K infall t = 0 t = 10 5 yr (?) 10/13/2014 5

6 SEDs from Dunham et al. (2013), PPVI review chapter Stages Classes Click single to edit isolated Master low-mass title star style n~ cm -3 T~ K Standard evolutionary scenario Class I protostar Wavelength (μm) outflow infall? igure adapted from McCaughrean, unpublished, by A. Stutz Flat spectrum Envelope dissipation? SED from Fischer et al. (in prep.) Class II YSO Solar system t = 10 5 yr (?) t = yr Protostar with disk Formation of 10/13/2014 6

7 Youngest YSOs in the Solar Neighborhood Click to edit Master title style Click to edit Master Perseus text styles Heiderman The majority of star formation is occurring in regions of dense gas that are very small fraction (20%) of the cloud area (Evans, Heiderman, & Vutisalchavakul 2014) 10/13/2014 7

8 Gas Surface Density Threshold (Σ Click to edit Master title style th ) YSOs + clumps are similar beyond gas threshold surface density: Σ gas > Σ th Σ th = 129±14 M pc 2 A V = 8 mag Slope changes» from Fifth ~5 level to ~ at Σ gas > Σ th Heiderman Low-mass YSOs Heiderman et al High-mass Clumps 10/13/2014 8

9 Gas Surface Density Threshold (Σ Click to edit Master title style th ) Lada, Lombardi, & Alves 2010 (independent methods) found Σ th ~116 Second M level pc 2 (A V ~7.3 mag) recovered a tight linear relation between SFR and total gas mass» Fifth Σ gas level > Σ th SFR M Dense 0.96 (Σ gas > Σ th ) Observational studies find Σ th ~ M pc 2 (A V ~7-10 ) (Onishi 1998; Johnstone 2004, Enoch+ 2007; André+ 2010, 2011, Könyves+ 2013, + others ) Lada, Lombardi, & Alves (2010) 10/13/2014 9

10 Is there some Universal star formation threshold? Click to edit Master title style Click Threshold to edit Model: Master text styles SFR (M Myr Second 1 ) = 0.046f level dense M Mol = 0.046M dense Σ gas > Σ th (A V >8 mag) Lada Lada proposed that possibly Galactic low mass star forming clouds above Av =8 lie in a linear relation with external galaxies (e.g., Gao & Solomon 2004a, b) Does this work in all clouds with low and high mass star formation? *and* external galaxies with different environments? Does this work in solar neighborhood filaments? 10/13/

11 Gould Belt HCO + MISFITS Survey: Click to edit Master title style The Real Solar Neighborhood Protostars Heiderman & Evans 2014, in prep) HCO + (3-2) survey of Young (Class 1/ Flat SED) YSOS CSO & APEX 550 YSOs surveyed (90% of all Class I & Flat SED, 5% of Class 2 sources) Pointings toward YSO locations confirm YSO (detect dense gas envelope) Based on van Kempen HCO + (4-3) stage 1 criteria strong line detections: T MB dv > 0.68 K km/s HCO + (3-2) Goal: provide a uniform Stage 1 source indicator for Gould Belt clouds Results: 320 Stage 1 protostars in the Gould Belt clouds 10/13/

12 Gould Belt HCO + MISFITS Survey: Click to edit Master title style The Real Solar Neighborhood Protostars 75% of all Class I or Flat SED YSOs Second lie in level regions of dense gas Third (A V level > 8 mag) 90% of Stage Fourth 1 protostars level (strong line detections) are at A V > 8 mag A V =8 mag (120 M pc 2 ) Stage 1 All Class I/Flat SED 10/13/

13 Herschel Aquila YSOs lie at High A V in Click to edit Master title style Click filaments to Könyves+ edit Master 2013 text styles Aquila Protostars A V > 7 mag Filaments 75% of Aquila YSOs are found above A V > 7 mag (70% in Orion) in Similarly, Smith find 75% of dense star-forming cores in a GMC Second simulation level were embedded within filaments Prestellar Cores, unstable filaments André A V ~8 Könyves /13/

14 A V Map Click to Faint edit Master Filament title style Click to edit Musca Master text styles Second Contours: level A V > 8 A V ranges ~2-12 mag 1 Class I YSO candidate at A V ~ 2 mag, weakly detected in HCO + MISFIT protostar 120 = 0.09 pc N. Cox+, in prep 10/13/

15 Filament Click to Hubs edit at Master High Atitle V style Click to Stage edit 1 protostars Master text styles Contours: A V > 8 NGC 1333 Image: Meyers 2009 Perseus 180 = 0.22 pc 10/13/

16 Click Filament to edit Hubs Master at High title Astyle V Image: Meyers 2009 Ophiuchus 270 = 0.15 pc Stage 1 protostars Contours: A V > 8 L /13/

17 Filaments at High A Click to edit Master V title style Aquila Prestellar Cores, unstable filaments André Contours: A V > 8 Stage 1 protostars 120 = 0.15 pc 10/13/

18 Filaments at High A Click to edit Master V title style Aquila Prestellar Cores, unstable filaments André Contours: A V > 8 Stage 1 protostars 120 = 0.15 pc 10/13/

19 Star Formation at High A Click to edit Master title style V Stage 1 protostars Contours: A V > 8 Auriga 120 = 0.32 pc 10/13/

20 Star Formation at High A Click to edit Master title style V Stage 1 protostars Contours: A V > 8 Auriga 120 = 0.32 pc 10/13/

21 Star Formation at High A Click to edit Master title style V Stage 1 protostars Contours: A V > 8 Auriga 120 = 0.32 pc 10/13/

22 Is there some Universal star formation threshold? Click to edit Master title style Click Threshold to edit Model: Master text styles SFR (M Myr Second 1 ) = 0.046f level dense M Mol = 0.046M dense Σ gas > Σ th (A V >8 mag) Lada Lada proposed that possibly Galactic low mass star forming clouds above Av =8 lie in a linear relation with external galaxies (e.g., Gao & Solomon 2004a, b) Does this work in all clouds with low and high mass star formation? *and* external galaxies with different environments? Does this work in solar neighborhood filaments? 10/13/

23 Is there some Universal star formation threshold? Click to edit Master title style log Gould Belt Clouds High-mass Clumps Stage 1 protostars in Filament Regions Lada Equation log Lada proposed that possibly Galactic low mass star forming clouds above Av =8 lie in a linear relation with external galaxies Lada equation aligns relatively well with Filament regions above A V = 8 as well as high-mass clumps (Wu+ 2010, Vutisalchavakul & Evans 2013, Evans+ 2014) Extending this to external galaxies needs testing w.r.t. which gas tracer to use 10/13/

24 Do YSO envelopes trace coherent structures? Click to edit Master title style N 2 H + map from CLASSy (Fernandez-Lopez+ 2014) HCO + velocity (km/s) pointed on stage 1 protostars Aquila N 2 H + / C 18 O Velocity field in Taurus cores continues the motion of the surrounding cloud material (Hacar+ 2013)- does HCO + trace coherent filament structures? 10/13/

25 Gradients in other clouds? Click to edit Master title style Does HCO + at stage 1 protostar position trace coherent filament structures? Auriga L1688 Oph HCO + velocity (km/s) pointed on stage 1 protostars NGC 1333 Perseus 10/13/

26 Summary Click to edit Master title style Stage 1 protostars Gould Belt HCO + MISFITS Survey provides a uniform Stage 1 strong line indicator and confirmed protostar sample 90% of the ~300 Stage 1 sources lie at high gas density (A V >8 mag; Σ gas > 120 M pc 2 ) Stage 1 protostars are found in filaments (Auriga, Aquila) and filament hubs (Perseus, Oph) at A V >8 Linear relation between dense gas mass and SFR in nearby Galactic clouds and high-mass clumps also agrees with Stage 1 sources in filamentary structures HCO + at Stage 1 protostar location traces kinematic structure of filaments 10/13/

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