[Paper Review] The Stellar Tidal Stream Survey

David Martínez‐Delgado|arXiv (Cornell University)|Nov 29, 2018

Space Exploration and Technology1 references4 citations

TL;DR

The Stellar Tidal Stream Survey uses a network of robotic amateur telescopes to conduct deep, wide-field imaging of Milky Way analog galaxies, revealing faint, large-scale tidal streams in their halos for the first time. These discoveries provide critical observational constraints on galaxy formation in the Lambda-Cold Dark Matter paradigm and enable future dynamical studies of dark matter halos using upcoming spectroscopic facilities like the ELT/MOSAIC instrument.

ABSTRACT

Mergers and tidal interactions between massive galaxies and their dwarf satellites are a fundamental prediction of the Lambda-Cold Dark Matter cosmology. These events are thought to influence galaxy evolution throughout cosmic history and to provide important observational diagnostics of structure formation. Stellar streams in the Local Group are spectacular evidence for satellite disruption at the present day. However, constructing a significant sample of tidal streams beyond our immediate cosmic neighborhood has proven a daunting observational challenge and their potential for deepening our understanding of galaxy formation has yet to be realized. Over the last decade, the Stellar Tidal Stream Survey has obtained deep, wide-field images of nearby Milky-Way analog galaxies with a network of robotic amateur telescopes, revealing for the first time an assortment of large-scale tidal structures in their halos. I discuss the main results of this project and future plans for performing dynamical studies of the discovered streams.

Motivation & Objective

• To identify and map faint tidal streams in the halos of nearby Milky Way-like galaxies, which are predicted by the Lambda-Cold Dark Matter (LCDM) model but difficult to observe due to low surface brightness.
• To overcome the observational challenge of detecting low-surface-brightness tidal features by using deep, wide-field imaging from a global network of robotic amateur telescopes.
• To build a sample of tidal stream candidates for future dynamical modeling, enabling tests of galaxy merger histories and dark matter halo properties.
• To determine whether the Milky Way's recent merger history is typical among spiral galaxies by comparing its tidal features to those in a broader sample of nearby galaxies.
• To identify the most promising tidal stream targets for future kinematic follow-up with next-generation spectrographs like MOSAIC on the ELT.

Proposed method

• Utilizing a network of robotic amateur telescopes with apertures between 0.1 and 0.5 meters to conduct deep, wide-field imaging of nearby spiral galaxies.
• Applying advanced image processing techniques to detect diffuse, low-surface-brightness structures (down to μ ≈ 26 mag/arcsec²) in the outer halos of galaxies.
• Comparing observed tidal features with predictions from cosmological simulations (e.g., Auriga, LCDM) to assess their consistency with satellite disruption and accretion histories.
• Focusing on morphological features such as radial (‘umbrella-like’) and great-circle streams, which are sensitive to dark matter halo density profiles and shapes.
• Using sky-projected stream morphology and future line-of-sight velocity measurements to break degeneracies in orbital modeling and constrain host galaxy potential.
• Prioritizing targets for spectroscopic follow-up based on stream surface brightness, morphology, and orbital orientation to maximize dynamical constraints.

Experimental results

Research questions

• RQ1 Are tidal streams in the halos of nearby Milky Way-like galaxies detectable with deep imaging from ground-based robotic telescopes?
• RQ2 How do the morphological and surface brightness properties of observed tidal streams compare to predictions from LCDM cosmological simulations?
• RQ3 Can tidal streams in nearby galaxies be used to infer the shape and density profile of their host galaxy’s dark matter halo?
• RQ4 Is the Milky Way’s recent merger history typical among spiral galaxies of similar mass?
• RQ5 Which tidal stream systems are optimal targets for future kinematic studies with the ELT/MOSAIC instrument?

Key findings

• The Stellar Tidal Stream Survey has detected large-scale, diffuse tidal structures in the halos of nearby galaxies, including NGC 5866 and NGC 4569, with surface brightness as faint as 26 mag/arcsec², using only amateur telescopes.
• The survey reveals that tidal features are common in the halos of spiral galaxies, supporting the LCDM prediction that minor mergers are a key mechanism in stellar halo formation.
• The morphology of detected streams—such as radial and great-circle configurations—provides direct observational evidence of past satellite accretion and orbital dynamics.
• The NGC 1097 tidal stream, with its unique radial geometry, allows for constraints on the host galaxy’s dark matter density profile using only a single kinematic point, demonstrating the power of morphological modeling.
• The survey has identified candidate streams with sufficient depth and structure to be viable targets for future spectroscopic follow-up with the ELT/MOSAIC instrument, which will enable high-precision velocity measurements of hundreds of stars.
• The results suggest that a sample of ~100 galaxies observed to a surface brightness limit of ~29 mag/arcsec² could reveal tens of detectable tidal features, validating the statistical power of deep surveys.