RESEARCH interests

1. physics and star formation in cold, dense galactic "clumps" and cores

• relying on Planck and Herschel detections (PGCC objects)
• physical parameters, kinematics, and stability of possible star-forming sites from dust continuum and molecular line emission
• correlations with galactic position, cloud morphology, environment, ongoing SF...
• to connect the governing processes of SF with observed environments and features, identify sites of very early star formation

Galactic Cold Cores research team (Herschel Key Programme, PIs: Mika Juvela, Isabelle Ristorcelli, supervisor: L. Viktor Toth)
TOP-SCOPE project (PI: Tie Liu)

INitial conditions of star formation

Planck: > 13,000 dense, cold, potentially star forming galactic structures ("clumps")

​     --> a possibility to study of the earliest phases of SF on a statistical sample
            nature of the objects, initial conditions, stages, timescales, environmental effects

Herschel: high resolution and sensitivity FIR maps of individual regions

credit: L. Montier

the STructure of the Tmc-1 filament

• dense, filamentary cloud in Taurus
• part of a bush-like group of Planck objects (Heiles Cloud 2) with complex morphology (ring?)
• high S/N and velocity resolution NH3 observations with the Effelsberg telescope as part of our survey of cold dense regions spanning several years

Fehér et al. 2016, A&A

• temperature and column density distribution + kinematics --> sub-structures
• close to equilibrium, chemical and dynamical age different in N and S subfilaments
• turbulence increased by an outflow of a nearby YSO reaching the main ridge

CO survey of Planck objects

• part of a systematic ground-based molecular emission survey of Planck objects
• correlation of continuum- and line-based densities, temperatures, determination of stability
• 35 clumps observed with two CO isotopologues with the Onsala 20m telescope

• most objects are cold, dense, rare traces of heating
• continuum- and line-based densities correlate well
• kinematic distances, stability estimates
• 2 object groups: close-by, core-sized, low-mass and gravitationally unbound clumps and massive, parsec-scale clouds farther away

Fehér et al. 2016, A&A

NH3 survey of planck objects in various environments

• part of the TOP-SCOPE collaboration measuring sub-mm continuum and many gas tracers towards/close to samples of Planck objects
• 100 dense clouds in varying environments (high-latitude, filamentary, in clusters close to the GP)
• pointed NH3 inversion transition measurements with the Effelsberg telescope (+ water maser)

Fehér et al. 2022, ApJSS

for the future: AMmonia surveys of the galactic cold ISM

• Effelsberg observations 2008-2016
• ~ 40 PGCC mapped NH3(1,1) and (2,2) transitions
  (Tóth, ..., Fehér, ..., in prep)
• connecting to galactic environment and ongoing SF
• individual objects studies:
  • ​the double core of G163.82-8.44
    (Zahorecz, ..., Fehér, ..., in prep.)
  • the clumps of Heiles Cloud 2
    (Fehér et al. in prep)

Research interests

2. circumstellar material of young stellar sources

• FU Orionis-type, low-mass, eruptive young stars
• millimeter radiointerferometric maps of the continuum and a number of molecular species/transitions with ALMA, NOEMA, JCMT, APEX
• tracing the envelope, the envelope/disk interface, the disk (distance!)
• morphology, kinematics, mass transfer...
• only a couple dozen of these objects but might answer interesting questions wrt: luminosity problem, universality of episodic accretion in low-mass SF, accretion processes

Momentum Disk Research Group (PI: Ágnes Kóspál) + SACCRED ERC project (PI: Ágnes Kóspál)

Interferometric view of the envelopes of Fu ori-type stars

• IRAM/NOEMA interferometric observations of northern FUors (CO and 2.7 mm continuum)
• size, mass, kinematics of envelope
• 14 objects to this date

• detection of "extended envelopes" on a 10,000 AU scale, clumpy structure
• heated, few 1000 AU envelopes centered on the stars, outflows
• envelope parameters suggest Class I and II sources - "normal" YSOs in a special state? evolutionary sequence?
• joint ALMA survey: more complicated picture

Fehér et al. 2017, A&A

Ábrahám, ..., Fehér, ..., 2017, ApJ

Kóspál, ..., Fehér, ..., 2021, ApJSS

MASS Transport around V346 Nor

• pilot study for our ALMA project on southern FU Ori-type objects
• CO isotopologues and 1.3 mm continuum with a resolution of ~1" (~700 AU)
• disk/envelope/outflow cavity mapping, mass, kinematics, morphology

• compact continuum, extended CO emission
• spectro-astrometry: outer pseudo-disk (rotation + infall), inner 350 AU keplerian disk
• the infall rate from the envelope to the disk is a factor of a few higher than the quiescent accretion rate --> mechanism of eruption

Kóspál, ... Fehér, ..., 2017, ApJ

FOR the future: joint study with ALMA, chemistry, and more

• ALMA study of > 10 FU Orionis-type objects
  • CO and continuum mapping to derive physical parameters, see structure and kinematics
• chemical study of FUors with single-dish measurements
  • ​IRAM, APEX
• resolving the envelope/disk interface with NOEMA
  • might reach spatial resolutions close to ALMA
  • dynamics of infall
• monitoring new FUor detections --> increasing the sample to disentangle the role of these objects and processes

skills acquired during my research

•  
• observation and data reduction/analysis experience using several radio telescopes (Effelsberg, Onsala, IRAM, JCMT)
• experience with planning/scheduling/reducing a diverse sample of scientific projects & a good view of the "everyday problems and challenges of telescope systems" as astronomer-on-duty at NOEMA
• utilisation of the GILDAS software package (CLASS, CLIC, MAPPING) for radiospectrostcopic data calibration, reduction, and analysis
• frequent usage of IDL, python, ds9
• writing and planning telescope proposals as PI and co-I (Effelsberg, IRAM 30m/NOEMA, APEX, ALMA)
• teaching and tutoring (observational astronomy to BSc students, supervision of summer projects and thesis work of MSc students)​
• organizing and participating at several workshops, scientific "Coffee Breaks"
• presenting at conferences (Herschel workshops, IAU, EWASS)