[Paper Review] Observing molecular hydrogen clouds and dark massive objects in galactic halos

F. De Paolis, G. Ingrosso+3 more|arXiv (Cornell University)|Jan 20, 1995

Astrophysics and Star Formation Studies3 citations

TL;DR

This paper proposes detecting molecular hydrogen clouds and dark massive objects (MHOs) in the M31 galactic halo using Doppler shift measurements and infrared emission. It demonstrates that molecular hydrogen clouds could contribute to halo dark matter and potentially form MHOs, with detectable signatures via redshifted emission lines and microlensing, offering a pathway to observe otherwise invisible massive structures in galactic halos.

ABSTRACT

Molecular hydrogen clouds can contribute substantially to the galactic halo< dark matter and may lead to the birth of massive halo objects (MHOs) observed indirectly by microlensing. We present a method to detect these molecular clouds in the halo of M31 using the Doppler shift effect. We also consider the possibility to directly observe MHOs in the halo of M31 via their infrared emission.

Motivation & Objective

• To investigate the role of molecular hydrogen clouds in contributing to galactic halo dark matter.
• To explore the formation of massive halo objects (MHOs) from these molecular clouds.
• To propose observational methods for detecting MHOs via microlensing and infrared emission.
• To develop a Doppler shift-based technique for identifying molecular hydrogen clouds in the M31 halo.
• To assess the feasibility of directly observing MHOs through their thermal infrared radiation.

Proposed method

• Using the Doppler shift effect to detect molecular hydrogen clouds in the M31 galactic halo by measuring redshifted emission lines.
• Analyzing the kinematic signatures of molecular hydrogen to infer the presence of massive, dark objects.
• Modeling the infrared emission from MHOs to determine detectability with current telescopes.
• Applying microlensing event statistics to indirectly infer the existence and mass distribution of MHOs.
• Combining molecular cloud dynamics with gravitational lensing to constrain halo dark matter content.
• Evaluating the detectability of molecular hydrogen in the halo through high-resolution spectroscopy of M31.

Experimental results

Research questions

• RQ1 Can molecular hydrogen clouds in the M31 halo be detected using Doppler shift measurements of their emission lines?
• RQ2 Do molecular hydrogen clouds contribute significantly to the dark matter content of galactic halos?
• RQ3 Can massive halo objects (MHOs) form from the collapse of molecular hydrogen clouds?
• RQ4 What infrared luminosity levels would MHOs need to produce for direct detection with current instruments?
• RQ5 How do microlensing events correlate with the presence of molecular hydrogen clouds and MHOs in the galactic halo?

Key findings

• Molecular hydrogen clouds in the M31 halo can be detected via Doppler-shifted emission lines, providing a direct observational signature.
• These clouds may constitute a significant fraction of the galactic halo's dark matter if their mass density is sufficient.
• MHOs formed from molecular cloud collapse could be observed indirectly through microlensing events.
• Infrared emission from MHOs may allow direct detection, especially if they are massive and warm.
• The combination of Doppler shift analysis and microlensing provides a multi-wavelength strategy for probing dark matter in galactic halos.
• The study establishes a feasible observational framework for detecting otherwise invisible massive objects in galactic halos.