Neutral Atomic Hydrogen in the solar neighborhood (NeAtHood)

Hydrogen is the most common atom in our Galaxy. Nine of every ten atoms in the sun are hydrogen. Two of every three atoms in our bodies are hydrogen. Ours is a story of hydrogen. But the story of how the hydrogen atoms in the Milky Way condense into clouds and how those clouds collapse to form stars like the sun, planets like the Earth, and living beings like us is yet to be told. Interstellar hydrogen clouds are the environment within which dense, star-forming clouds reside. Studying their structure and properties around star-forming regions is exploring the relics of the conditions that lead to the nearby matter organization as we see it today. This project uses the main tracer of neutral interstellar hydrogen, its emission at a 21-centimeter wavelength. This type of light is in the range of radio waves, at around twice the wavelength employed to transmit the Wi-Fi signals. Gathering the 21-cm wavelength light from the hydrogen gas in and around star- forming regions requires some of the largest telescopes on Earth. This project uses observations made with the Karl G. Jansky Very Large Array (VLA), an observatory located at a 2,124-meter altitude on the Plains of San Agustin in central New Mexico, United States. The VLA comprises twenty-eight 25-meter-diameter single-dish telescopes deployed in a Y-shaped array. Their observations are combined using the technique known as interferometry, which mixes the signals from each telescope to produce images with greater detail than those obtained with each instrument separately. This project uses the VLA in a configuration that reproduces a one-kilometer-sized telescope. That is twice the size of the largest single-dish telescope on Earth. These observations will produce unprecedented images of the flows that assemble star-forming regions and the eruptions propelled by the energy input from the newly- born stars, thus providing insight into key processes of the matter cycle in our galaxy. This project uses novel analysis techniques to gather all the possible information from the new observations. It employs the same principles applied in online image search and signal processing to identify long-term trends in weather and stock-market data. The techniques are tailored to identify the conditions that favor the appearance of star-forming regions and determine how those regions exchange energy and matter with their environments. Star-forming regions are complex systems; we only see snapshots of their lives in astronomical images. Reconstructing their evolution in time is like trying to tell the story of a family just looking at their photo albums. Therefore, this project also uses computer simulations to reproduce the possible scenarios through which star-forming clouds come to be, grow, and eventually disperse. Through its findings, this project will reveal the connections that produce new stars near the Sun, revealing the workings of our interstellar ecosystem.