A step in the dark: dense molecular gas in galaxies

Lead Research Organisation: CARDIFF UNIVERSITY
Department Name: School of Physics and Astronomy

Abstract

All the stars that exist in our Galaxy and in all other galaxies that are scattered throughout the Universe were formed
deep inside giant clouds of molecular hydrogen gas with sizes of hundreds of light years and masses of a million suns
or more. It is in such interstellar regions where dense hydrogen gas condenses via its self-gravity and cools down so it
can form the new stars and the planets around them, yet until now such regions have been mostly out of reach for astronomers.
This is simply because the cold interstellar gas does not emit radiation at optical wavelengths but at the much longer infrared (IR)
and millimetre and sub-millimetre wavelengths. Moreover, even if it did, any optical (and even IR) radiation from such regions
of interstellar space would be almost totally absorbed by the interstellar dust mixed with the molecular hydrogen of these
large gas clouds. Thus the now well-developed tools of optical and IR astronomy are unable to tell us anything about the
places where new Suns are created, and only a small smattering of millimetre and sub-millimetre telescopes have
been able to do so. One of them is the famed James Clerk Maxwell Telescope (JCMT) atop Mauna Kea in Hawaii
at 4092 meters altitude, built by the UK, with Canada and The Netherlands supplying many of its instruments.
The proposed project, initiated at the JCMT, will fully explore the properties of this important phase of interstellar
gas, and study its effects on the stars formed. It will take advantage of the truly new era that will open up in
observational astronomy with the now spaceborne Herschel Space Observatory, and the commissioning
of the Atacama Large Millimeter Array (ALMA) at 5100 meters altitude in the Atacama desert in North
Chile. The later, with 50 radiotelescopes of 12-meters diameter each is the largest ground-based observatory
on the planet and will at last give astronomers an unhindered view at mm/submm wavelengths. The proposed
study will help usher this new era by using these new facilities to study the most important component of the
Interstellar Medium, and its relation to the formation of stars in the Universe.

Publications

10 25 50
 
Description Me and my small team have discovered:

1) A new way to trace molecular hydrogen in the Universe
...a Universe where all its stars are formed out of that gas.
So knowing where H2 gas is in the Universe is knowing
where new stars can form.

2) That the cosmic rays, particles racing through the galaxies
caught by their magnetic fields, affect the conditions under
which stars form in galaxies, deep inside vast clouds of H2
gas, where light cannot penetrate.

Both discoveries will open up new avenues of research
in Astrophysics, with guaranteed impact in many sub-fields
of this research discipline

Finally, we recently discovered that cosmic rays may destroy
the most widespread molecule in the Universe after H2 itself,
namely carbon monoxide (CO), rendering H2 'invisible' to
the standard method of tracing it via the CO mixed with it.
This makes discovery No1 even more important
Exploitation Route They will impact *all* fields of Astrophysics that need
estimates of H2 gas distribution, and the initial conditions
of star formation in the Universe
Sectors Other

 
Description ESO visitorship program
Amount € 7,500 (EUR)
Organisation European Southern Observatory (ESO) 
Sector Charity/Non Profit
Country Germany
Start 05/2016 
End 12/2016
 
Title Large Velocity Gradient Radiative transfer and pdf analysis 
Description This is a comprehensive method for modelling large data sets of molecular lines from galaxies in the Universe 
Type Of Material Improvements to research infrastructure 
Year Produced 2014 
Provided To Others? Yes  
Impact It will impact the entire field of molecular Astrophysics in the age of ALMA as it is the only one capable to deal with the large number of lines detected by this radio telescope array 
URL http://adsabs.harvard.edu/abs/2014ApJ...788..153P
 
Description ALMA observations of a nearby starburst galaxy 
Organisation University of Hawaii
Department Institute for Astronomy
Country United States 
Sector Academic/University 
PI Contribution This is an ambitious program to test both a new way to detect H2 mass in the Universe as well as detect its velocity field around galaxies. I have contributed the main ideas and computations.
Collaborator Contribution Dr Cicone of ETH wrote the ALMA proposal, and is currently doing the analysis of the data. A paper is under preparation.
Impact There is a paper being written for the Astrophysical Journal, and another set of proposals being prepared for ALMA and APEX (a radio telescope in North Chile).
Start Year 2014
 
Description Cosmic rays and the initial conditions of star formation 
Organisation University of Hawaii
Department Institute for Astronomy
Country United States 
Sector Academic/University 
PI Contribution This is a collaboration with Dr Francesco Miniati, where I have provided the initiative and some of the main ideas in the study of Cosmic Rays as the regulators of initial conditions of star formation in Galaxies
Collaborator Contribution Dr Miniati is contributing his modeling expertise on the propagation of cosmic rays in the magnetic fields of galaxies
Impact This research has already given us a much better view of what sets the initial conditions of star formation in galaxies, and opened a new avenue of research with ALMA
Start Year 2013
 
Description Gone with heat: A fundamental constraint on imaging gas and dust in the early Universe 
Organisation European Southern Observatory (ESO)
Country Germany 
Sector Charity/Non Profit 
PI Contribution I have contributed the main idea on the fundamental constraint set by the Cosmic Microwave Background (CMB) radiation on the imaging of galaxies and their cold interstellar medium (ISM) in the Early Universe. I also developed the mathematical tools for modeling this.
Collaborator Contribution Dr Zhi-Yu of ESO is actually implementing the main idea and my models using three nearby galaxies and their Herschel data
Impact There is a paper that has been submitted to the Royal Society Journal with No: ID RSOS-160025.
Start Year 2014
 
Description H2 gas in the Universe 
Organisation European Southern Observatory (ESO)
Country Germany 
Sector Charity/Non Profit 
PI Contribution I gave a series of seminars to the Astronomers of ESO regarding the H2 gas in the Universe and methods to trace its conditions and mass
Collaborator Contribution They listened and asked probing questions
Impact Several ALMA and APEX proposal were inspired by this series of talks
Start Year 2014
 
Description High-J CO lines of SPT galaxies 
Organisation European Southern Observatory (ESO)
Country Germany 
Sector Charity/Non Profit 
PI Contribution I have conducted observations with the APEX telescope in Chile and provided some of the main ideas of this project, whose PI is Carlos De Breuck
Collaborator Contribution Carlos De Breuck wrote the APEX proposal, and provided the PhD student, Bitten Gulleberg that interpreted the final dataset
Impact There is a paper being prepared for the Astrophysical Journal
Start Year 2013
 
Description The interstellar medium in Galaxies 
Organisation Academy of Athens
Department Research Center for Astronomy
Country Greece 
Sector Academic/University 
PI Contribution I bring in the Academy of Athens some unique expertise on the interstellar medium, in a place dominated by people that study dynamics of galaxies
Collaborator Contribution They provide me with the infrastructure for long term stays (own office, computer, access to the building and computational resources), as well as indispensable on galactic dynamics
Impact Two papers have been written while I was in residence in the Academy of Athens. There is the discipline of Mathematics, involved in the non-linear models of galactic dynamics that the people in the Academy of Athens develop.
Start Year 2012
 
Description On the verge of other worlds 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I have given a popular talk about the telescopes on Mauna Kea in Hawaii
to the general audience in the city of Katerini, Macedonia, Greece.
It has sparked numerous questions afterwards
Year(s) Of Engagement Activity 2015
 
Description The adventure of Astronomy (school visit in Xatzikiriakio School of Athens) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact I have given a talk about what it takes to go up and do observations on the
Mauna Kea Deep Space Observatories in Hawaii to High School students,
in a school for orphaned children in Athens/Piraeus.
Year(s) Of Engagement Activity 2013,2014,2016
 
Description What an astrophycist does 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was an event organized by the Academy of Athens for the general public
in a series of such events organized in the main building of the Academy, in the
center of Athens.
Year(s) Of Engagement Activity 2015