Search for PAHs in the Perseus molecular cloud with the Green Bank Telescope

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are believed to be the small-size tail of the interstellar carbonaceous dust grain population. Their vibrational emission is the most widely accepted source of the aromatic near-infrared features, and their rotational radiation is a likely explanation for the dust-correlated anomalous microwave emission (AME). Yet, no individual interstellar PAH molecule has been identified to date. It was recently recognized that quasi-symmetric planar PAHs ought to have a well identifiable comb-like rotational spectrum, and suggested to search for them in spectroscopic data with matched-filtering techniques. We report the results of the first such search, carried out with the Green Bank Telescope, and targeting the star-forming region IC348 in the Perseus molecular cloud, a known source of AME. Our observations amounted to 16.75 hours and spanned a 3 GHz-wide band extending from 23.3 to 26.3 GHz. Using frequency switching, we achieved a sensitivity of 0.4 mJy per 0.4 MHz channel (1-sigma). The non-detection of comb-like spectra allowed us to set upper bounds on the abundance of specific quasi-symmetric PAH molecules (specified uniquely by their moments of inertia) of approximately 0.1% of the total PAH abundance. This bound generically applies to PAHs with approximately 15 to 100 carbon atoms.

11 pages, 11 figures

References in corpus (11)

• An Accurate Flux Density Scale from 1 to 50 GHz
• A refined model for spinning dust radiation
• Unidentified Infrared Emission bands: PAHs or MAONs?
• The Carriers of the Interstellar Unidentified Infrared Emission Features: Aromatic or Aliphatic?
• The Carriers of the Interstellar Unidentified Infrared Emission Features: Constraints from the Interstellar C-H Stretching Features at 3.2-3.5 Micrometers
• A general model for the identification of specific PAHs in the far-IR
• Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission
• Rotational spectroscopy of interstellar PAHs
• AMI Observations of the Anomalous Microwave Emission in the Perseus Molecular Cloud
• Spinning dust radiation: a review of the theory
• Constraints on free-free emission from Anomalous Microwave Emission Sources in the Perseus Molecular Cloud

Cited by in corpus (4)

• The Astrodust+PAH Model: A Unified Description of the Extinction, Emission, and Polarization from Dust in the Diffuse Interstellar Medium
• The State-of-Play of Anomalous Microwave Emission (AME) Research
• Rotational spectra of interstellar N- and CN-PAHs: pyrene and coronene
• Reaction kinetics of CN + toluene and its implication on the productions of aromatic nitriles in the Taurus molecular cloud and Titan's atmosphere