Star formation across the mass spectrum Our understanding of low-mass (solar type with masses between 0.1 and 10 M SUN ) star formation has improved greatly.

Slides:



Advertisements
Similar presentations
Masers and Massive Star Formation Claire Chandler Overview: –Some fundamental questions in massive star formation –Clues from masers –Review of three regions:
Advertisements

Star Birth How do stars form? What is the maximum mass of a new star? What is the minimum mass of a new star?
The W i d e s p r e a d Influence of Supermassive Black Holes Christopher Onken Herzberg Institute of Astrophysics Christopher Onken Herzberg Institute.
The Birth of Stars Chapter Twenty. Guiding Questions 1.Why do astronomers think that stars evolve? 2.What kind of matter exists in the spaces between.
The Birth of Stars Chapter Twenty. Interstellar gas and dust pervade the Galaxy Interstellar gas and dust, which make up the interstellar medium, are.
The Birth of Stars: Nebulae
Stellar Evolution up to the Main Sequence. Stellar Evolution Recall that at the start we made a point that all we can "see" of the stars is: Brightness.
Protostars, nebulas and Brown dwarfs
Formation of Stars Physics 113 Goderya Chapter(s):11 Learning Outcomes:
Some examples of Type I supernova light curves Narrow range of absolute magnitude at maximum light indicates a good Standard Candle B band absolute magnitude.
From Pre-stellar Cores to Proto-stars: The Initial Conditions of Star Formation PHILIPPE ANDRE DEREK WARD-THOMPSON MARY BARSONY Reported by Fang Xiong,
Roger A. Freedman • William J. Kaufmann III
Chapter 19.
The Milky Way PHYS390 Astrophysics Professor Lee Carkner Lecture 19.
© 2010 Pearson Education, Inc. Chapter 21 Galaxy Evolution.
Formation of Massive Stars With great advances achieved in our understanding of low mass star formation, it is tempting to think of high mass star formation.
ASTR100 (Spring 2008) Introduction to Astronomy Galaxy Evolution & AGN Prof. D.C. Richardson Sections
Centimeter and Millimeter Observations of Very Young Binary and Multiple Systems -Orbital Motions and Mass Determination -Truncated Protoplanetary Disks.
Star Formation Astronomy 315 Professor Lee Carkner Lecture 12.
Dusty star formation at high redshift Chris Willott, HIA/NRC 1. Introductory cosmology 2. Obscured galaxy formation: the view with current facilities,
Á L V A R O S Á N C H E Z M O N G E B A R C E L O N A - N O V E M B E R 23, 2006 Centimeter and Millimeter Emission from Selected High-Mass Star-Forming.
Star and Planet Formation Sommer term 2007 Henrik Beuther & Sebastian Wolf 16.4 Introduction (H.B. & S.W.) 23.4 Physical processes, heating and cooling.
STAR BIRTH. Guiding Questions Why do astronomers think that stars evolve? What kind of matter exists in the spaces between the stars? Where do new stars.
Chapter 19 Star Formation (Birth) Chapter 20 Stellar Evolution (Life) Chapter 21 Stellar Explosions (Death) Few issues in astronomy are more basic than.
Chapter 4: Formation of stars. Insterstellar dust and gas Viewing a galaxy edge-on, you see a dark lane where starlight is being absorbed by dust. An.
The Milky Way Appears as a band of light stretching across the sky There are dark regions along the band, giving the appearance of a lack of stars This.
Ionized gas in massive star forming regions Guido Garay Universidad de Chile Great Barriers in High-Mass Star Formation Townsville, September 15, 2010.
Astronomy 1020-H Stellar Astronomy Spring_2015 Day-33.
© 2005 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their.
Star Formation. Introduction Star-Forming Regions The Formation of Stars Like the Sun Stars of Other Masses Observations of Brown Dwarfs Observations.
Copyright © 2010 Pearson Education, Inc. Life Cycle of the Stars.
Quasars, black holes and galaxy evolution Clive Tadhunter University of Sheffield 3C273.
A105 Stars and Galaxies  This week’s units: 60, 61, 62, 4  News Quiz Today  Star Clusters homework due Thursday  2nd Exam on Thursday, Nov. 2 Today’s.
Star Formation in our Galaxy Dr Andrew Walsh (James Cook University, Australia) Lecture 1 – Introduction to Star Formation Throughout the Galaxy Lecture.
Chapter 19 Star Formation
Imaging gaps in disks at mid-IR VLT VISIR image 8.6 PAH 11.3 PAH 19.8  m large grains => gap! Geers et al IRS48 -Gap seen in large grains, but NOT.
© 2010 Pearson Education, Inc. Chapter 21 Galaxy Evolution.
January 2nd 2013 Objective Warm-Up
Chapter 15: Star Formation and the Interstellar Medium.
Science with continuum data ALMA continuum observations: Physical, chemical properties and evolution of dust, SFR, SED, circumstellar discs, accretion.
Seeing Stars with Radio Eyes Christopher G. De Pree RARE CATS Green Bank, WV June 2002.
Studying Young Stellar Objects with the EVLA
The Early Stages of Star Formation Leo Blitz UC Berkeley Space, Time and Life – August 26, 2002.
The Interstellar Medium and Star Formation Material between the stars – gas and dust.
ASTR 113 – 003 Spring 2006 Lecture 04 Feb. 15, 2006 Review (Ch4-5): the Foundation Galaxy (Ch 25-27) Cosmology (Ch28-39) Introduction To Modern Astronomy.
Chapter 11 The Interstellar Medium
Please press “1” to test your transmitter
Chapter 11 The Interstellar Medium
The “ Local Group ” of Galaxies Two large spiral galaxies Milky Way & Andromeda (Messier 31 or M31) Distance between them: D = 700 kpc = 2.3 x 10 6 light.
Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.
Early O-Type Stars in the W51-IRS2 Cluster A template to study the most massive (proto)stars Luis Zapata Max Planck Institut für Radioastronomie, GERMANY.
In previous episodes …... Stars are formed in the spiral arms of the Galaxy, in the densest and coldest regions of the interstellar medium, which are.
1)The environment of star formation 2)Theory: low-mass versus high-mass stars 3)The birthplaces of high-mass stars 4)Evolutionary scheme for high-mass.
1 The “ Local Group ” of Galaxies Two large spiral galaxies Milky Way & Andromeda (Messier 31 or M31) Distance between them: D = 700 kpc = 2.3 x 10 6 light.
Centro de Radioastronomía y Astrofísica, UNAM. Massive Massive Star Formation Introduction The paradigm for low-mass star formation The search for jets.
Chapter 21 Galaxy Evolution Looking Back Through Time Our goals for learning How do we observe the life histories of galaxies? How did galaxies.
KASI Galaxy Evolution Journal Club A Massive Protocluster of Galaxies at a Redshift of z ~ P. L. Capak et al. 2011, Nature, in press (arXive: )
Universe Tenth Edition
H205 Cosmic Origins  Today: The Origin of Stars  Begin EP 6  Tuesday Evening: John Mather  7:30 Whittenberger APOD.
ISM & Astrochemistry Lecture 1. Interstellar Matter Comprises Gas and Dust Dust absorbs and scatters (extinguishes) starlight Top row – optical images.
“Globular” Clusters: M15: A globular cluster containing about 1 million (old) stars. distance = 10,000 pc radius  25 pc “turn-off age”  12 billion years.
Guiding Questions Why do astronomers think that stars evolve? What kind of matter exists in the spaces between the stars? Where do new stars form? What.
Star Formation. Chapter 19 Not on this Exam – On the Next Exam!
Stellar Birth Dr. Bill Pezzaglia Astrophysics: Stellar Evolution 1 Updated: 10/02/2006.
A Star is Born! Giant molecular clouds: consist of mostly H2 plus a small amount of other, more complex molecules Dense cores can begin to collapse under.
Star Formation.
Star Chapter 19: A Traumatic Birth
The Birth of Stars.
-Orbital Motions and Mass Determination
Phys./Geog. 182 Week 7 – Mon. - The Birth of Stars
Presentation transcript:

Star formation across the mass spectrum Our understanding of low-mass (solar type with masses between 0.1 and 10 M SUN ) star formation has improved greatly in the last few decades. Can we extend the model to high mass stars and to brown dwarfs? Presentation that emphasizes radio results. Luis F. Rodríguez, CRyA, UNAM

a)Fragmentation of cloud b)Gravitational contraction c)Accretion and ejection d)Formation of disk e)Residual disk f)Formation of planets (Shu, Adams & Lizano 1987) LOW MASS STAR FORMATION

Complementarity of observations at different bands. Reipurth et al. (2000) HST + VLA

HII Regions I (0) is blackbody function at T bg = 2.7 K (the cosmic microwave background). F is blackbody function at T ex  10,000 K (the electron temperature of the ionized gas). Neglect I (0) to get Since S =  I ,, and using R-J approximation:

HII Regions For (more or less) homogeneous HII region,  is approximately constant with. We then have the two limit cases for  > 1 (low frequencies) and for  < 1 (high frequencies): S  2 (optically thick) S  -0.1 (optically thin) log log S

Thermal Jets n e   -2  l  l   We define  c when  (  c ) = 1 Then  c  -0.7 => size of source decreases with ! Since S  2  2 c   0.6   -0.7 S  0.6

VLA 1 in HH 1-2 VLA 6cm

Dust Emission I (0) is blackbody function at T bg = 2.7 K (the cosmic microwave background). F is blackbody function at T d  K (the temperature of the dust). Neglect I (0) to get Since S =  I ,, and using R-J approximation:

Dust Emission For (more or less) homogeneous dust region,  is approximately constant with. We then have the two limit cases for  > 1 (low frequencies) and for  < 1 (high frequencies): S  2 (optically thick at high, IR wavelengths) S  2-4 (optically thin at low, millimeter wavelenghts) Power law index of opacity depends, to first approximation, on relative sizes between grain of dust and wavelength of radiation: a >  0

Dust Emission If dust is optically thin: ; and since If you know flux density, dust temperature, distance to source, and opacity characteristics of dust, you can get M d. Assume dust to gas ratio and you get total mass of object.

Dust emission at 7 mm VLA, Wilner et al.

Face-on disk

Dust emission from compact protoplanetary disk in Rho Oph

R-band HST images by Watson et al. of HH 30 Now, there is no doubt that solar mass stars form surrounded by protoplanetary disks and driving collimated outflows.

What about brown dwarfs? The field of brown dwarf formation is very young, but there is evidence of the existence of disks and outflows associated with them and even of the formation of planets in their disks…

Pascucci et al. (2005) argue that SED in this brown dwarf is well explained by dust emission in a disk. M(BD) = 70 MJ L(BD) = 0.1 L(sun) M(disk) about 1 MJ Dimensions of disk are not given since no images are available. Data from ISOCAM, JCMT, and IRAM 30m

Spectro-astrometric observations of Whelan et al. (2005) show blueshifted features attributed to outflow (microjets). Lack of redshifted features attributed to obscuring disk. Brown dwarf is Rho Oph 102 with mass of 60 MJ. Data from Kueyen 8m VLT telescope.

Presence of crystalline silicate in these six brown dwarfs (Apai et al. 2005) is taken to imply growth and crystallization of sub-micron size grains and thus the onset of planet formation. Data from Spitzer Space Telescope.

Formation of Massive Stars With great advances achieved in our understanding of low mass star formation, it is tempting to think of high mass star formation simply as an extension of low mass star formation. However…

Problems with the study of massive star formation(1) Kelvin-Helmholtz time  The more massive the star, the less time it spends in the pre-main sequence…

Problems with the study of massive star formation(2) Rate of massive star formation in the Galaxy  Massive, pre-main sequence stars are very rare…

Some problems with extending the picture of low- mass star formation to massive stars: Radiation pressure acting on dust grains can become large enough to reverse the infall of matter: –F grav = GM * m/r 2 –F rad = L  /4  r 2 c –Above 10 M sun radiation pressure could reverse infall

So, how do stars with M * >10M  form? Accretion: –Need to reduce effective  e.g., by having very high M acc –Reduce the effective luminosity by making the radiation field anisotropic Form massive stars through collisions of intermediate-mass stars in clusters –May be explained by observed cluster dynamics –Possible problem with cross section for coalescence –Observational consequences of such collisions?

Other differences between low- and high-mass star formation Physical properties of clouds undergoing low- and high- mass star formation are different: –Massive SF: clouds are warmer, larger, more massive, mainly located in spiral arms; high mass stars form in clusters and associations –Low-mass SF: form in a cooler population of clouds throughout the Galactic disk, as well as GMCs, not necessarily in clusters Massive protostars luminous but rare and remote Ionization phenomena associated with massive SF: UCH II regions Different environments observed has led to the suggestion that different mechanisms (or modes) apply to low- and high-mass SF

Still, one can think in 3 evolutionary stages: Massive, prestellar cold cores: Star has not formed yet, but molecular gas available (a few of these cores are known) Massive hot cores: Star has formed already, but accretion so strong that quenches ionization => no HII region (tens are known). Jets and disks expected in standard model Ultracompact HII region: Accretion has ceased and detectable HII region exists (many are known)