Excessive or inadequate weight gain during pregnancy poses numerous health risks for both pregnant individuals and children. Excessive GWG is associated with a higher risk of pregnancy complications, including pregnancy-related hypertension and greater long-term postpartum weight retention. Excessive GWG is also associated with the risk for childhood asthma and obesity. Earlier research by Columbia Mailman researchers found that GWG was linked with a three-fold increased risk of childhood obesity at age 7 and excessive maternal weight gain.

Neighborhood walkability refers to urban form characteristics that support and favor walking and is defined by criteria including population density, land-use mix, density of public transit infrastructure, and street connectivity. Residents of walkable neighborhoods have been shown to engage in more walking, greater overall physical activity, and to have lower body mass index (BMI). Walkable neighborhoods are associated with better control of blood sugar among people with Type II diabetes. The most walkable areas of New York City include Battery Park City, Greenwich Village, NoHo, SoHo, Little Italy, and the West Village (Manhattan CBs 1 and 2). The least walkable areas include neighborhoods in eastern Queens and parts of Staten Island (Queens CB13 and Staten Island CB2).

“Given the long-lasting benefits of healthy pregnancies for parental and child health, this research provides further impetus for the use of urban design and poverty reduction to support healthy weight and reduce the risk of excessive gestational weight gain and related health risks,” says the study’s first author, Eliza Kinsey, PhD, formerly a postdoctoral research scientist in the Department of Epidemiology, now an assistant professor at the University of Pennsylvania Perelman School of Medicine.

The current study was conducted in partnership with researchers at the New York City Department of Health and Mental Hygiene (DOHMH) Bureau of Vital Statistics and used de-identified birth record data for the year 2015 to examine neighborhood-level influences on GWG. Using medical record data, the DOHMH compiles data on all live births in the city, including basic health and demographic information for the pregnant individual and birth outcome statistics (e.g., birth weight, gestational age).

Among the sample of 106,285 births, 42 percent of the pregnant individuals experienced excessive GWG, and 26 percent had inadequate GWG. Pregnant people living in neighborhoods ranking among the poorest quarter of the city had an additional 17 percent greater odds of excessive GWG. Pregnant people living in the top quarter of neighborhoods ranked for walkability had 13 percent lower odds of excessive GWG. These findings align with prior studies in New York City that have found that both neighborhood poverty and walkability predict BMI in the general population.

Adjustment for pre-pregnancy BMI attenuated the association between neighborhood poverty and excessive GWG but had little impact on the association between neighborhood walkability and excessive GWG.

Senior author Andrew Rundle, DrPH, professor of epidemiology, noted: “Neighborhood walkability is likely associated with GWG due to differences in behavior during pregnancy, presumably walking for exercise and daily activities — not solely by influences on pre-pregnancy BMI. A significant amount of the exercise pregnant people get comes from low-impact activities like walking. Making neighborhoods more walkable has a host of health benefits, both for those currently living there and future generations.”

Co-authors of the current study include Elizabeth Widen, University of Texas at Austin; James Quinn, Columbia Mailman; Mary Huynh and Gretchen Van Wye, New York City Department of Health and Mental Hygiene; Gina Lovasi, Drexel University, Philadelphia; and Kathryn Neckerman, Columbia University Population Research Center.

The study was supported by Eunice Kennedy Shriver National Institute of Child Health and Human Development (grants HD101657, HD086304, HD042849)

Stretching up to 150 light years long, the one-dimensional strands (or filaments) are found in pairs and clusters, often stacked equally spaced, side by side like strings on a harp. Using observations at radio wavelengths, Northwestern University’s Farhad Yusef-Zadeh discovered the highly organized, magnetic filaments in the early 1980s. The mystifying filaments, he found, comprise cosmic ray electrons gyrating the magnetic field at close to the speed of light. But their origin has remained an unsolved mystery ever since.

Now, the new image has exposed 10 times more filaments than previously discovered, enabling Yusef-Zadeh and his team to conduct statistical studies across a broad population of filaments for the first time. This information potentially could help them finally unravel the long-standing mystery.

The study was published online today by The Astrophysical Journal Letters.

“We have studied individual filaments for a long time with a myopic view,” said Yusef-Zadeh, the paper’s lead author. “Now, we finally see the big picture — a panoramic view filled with an abundance of filaments. Just examining a few filaments makes it difficult to draw any real conclusion about what they are and where they came from. This is a watershed in furthering our understanding of these structures.”

Yusef-Zadeh is a professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).

Constructing the image

To construct the image with unprecedented clarity and detail, astronomers spent three years surveying the sky and analyzing data at the South African Radio Astronomy Observatory (SARAO). Using 200 hours of time on SARAO’s MeerKAT telescope, researchers pieced together a mosaic of 20 separate observations of different sections of the sky toward the center of the Milky Way galaxy, 25,000 light years from Earth.

The full image will be published in an additional, accompanying paper — led by Oxford University astrophysicist Ian Heywood and co-authored by Yusef-Zadeh — in a forthcoming issue of The Astrophysical Journal. Along with the filaments, the image captures radio emissions from numerous phenomena, including outbursting stars, stellar nurseries and new supernova remnants.

“I’ve spent a lot of time looking at this image in the process of working on it, and I never get tired of it,” Heywood said. “When I show this image to people who might be new to radio astronomy, or otherwise unfamiliar with it, I always try to emphasize that radio imaging hasn’t always been this way, and what a leap forward MeerKAT really is in terms of its capabilities. It’s been a true privilege to work over the years with colleagues from SARAO who built this fantastic telescope.”

To view the filaments at a finer scale, Yusef-Zadeh’s team used a technique to remove the background from the main image in order to isolate the filaments from the surrounding structures. The resulting picture astounded him.

“It’s like modern art,” he said. “These images are so beautiful and rich, and the mystery of it all makes it even more interesting.”

What we know

While many mysteries surrounding the filaments remain, Yusef-Zadeh has been able to piece together more of the puzzle. In their latest paper, he and his collaborators specifically explored the filaments’ magnetic fields and the role of cosmic rays in illuminating the magnetic fields.

The variation in radiation emitting from the filaments is very different from that of the newly uncovered supernova remnant, suggesting that the phenomena have different origins. It is more likely, the researchers found, that the filaments are related to past activity of the Milky Way’s central supermassive black hole rather than coordinated bursts of supernovae. The filaments also could be related to enormous, radio-emitting bubbles, which Yusef-Zadeh and collaborators discovered in 2019.

And, while Yusef-Zadeh already knew the filaments are magnetized, now he can say magnetic fields are amplified along the filaments, a primary characteristic all the filaments share.

“This is the first time we have been able to study statistical characteristics of the filaments,” he said. “By studying the statistics, we can learn more about the properties of these unusual sources.

“If you were from another planet, for example, and you encountered one very tall person on Earth, you might assume all people are tall. But if you do statistics across a population of people, you can find the average height. That’s exactly what we’re doing. We can find the strength of magnetic fields, their lengths, their orientations and the spectrum of radiation.”

What we don’t know

Among the remaining mysteries, Yusef-Zadeh is particularly puzzled by how structured the filaments appear. Filaments within clusters are separated from one another at perfectly equal distances — about the distance from Earth to the sun.

“They almost resemble the regular spacing in solar loops,” he said. “We still don’t know why they come in clusters or understand how they separate, and we don’t know how these regular spacings happen. Every time we answer one question, multiple other questions arise.”

Yusef-Zadeh and his team also still don’t know whether the filaments move or change over time or what is causing the electrons to accelerate at such incredible speeds.

“How do you accelerate electrons at close to the speed of light?” he asked. “One idea is there are some sources at the end of these filaments that are accelerating these particles.”

What’s next

Yusef-Zadeh and his team are currently identifying and cataloging each filament. The angle, curve, magnetic field, spectrum and intensity of each filament will be published in a future study. Understanding these properties will give the astrophysics community more clues into the filaments’ elusive nature.

The MeerKAT telescope, which launched in July 2018, will continue to unveil new secrets.

“We’re certainly one step closer to a fuller understanding,” Yusef-Zadeh said. “But science is a series of progress on different levels. We’re hoping to get to the bottom of it, but more observations and theoretical analyses are needed. A full understanding of complex objects takes time.”

The study, “Statistical properties of the population of the galactic center filaments: The spectral index and equipartition magnetic field,” was supported by NASA and the National Science Foundation.

The scientists used the NOEMA (Northern Extended Millimeter Array) observatory in the French Alps, the most powerful radio telescope in the Northern Hemisphere, to observe HFLS3, a massive starburst galaxy at a distance corresponding to an age of only 880 million years after the Big Bang. They discovered a screen of cold water gas that casts a shadow on the cosmic microwave background radiation. The shadow appears because the colder water absorbs the warmer microwave radiation on its path towards Earth, and its darkness reveals the temperature difference. As the temperature of the water can be determined from other observed properties of the starburst, the difference indicates the temperature of the Big Bang’s relic radiation, which at that time was about seven times higher than in the Universe today.

‘Besides proof of cooling, this discovery also shows us that the Universe in its infancy had some quite specific physical characteristics that no longer exist today,’ said lead author Professor Dr Dominik Riechers from the University of Cologne’s Institute of Astrophysics. ‘Quite early, about 1.5 billion years after the Big Bang, the cosmic microwave background was already too cold for this effect to be observable. We have therefore a unique observing window that opens up to a very young Universe only,’ he continued. In other words, if a galaxy with otherwise identical properties as HFLS3 were to exist today, the water shadow would not be observable because the required contrast in temperatures would no longer exist.

‘This important milestone not only confirms the expected cooling trend for a much earlier epoch than has previously been possible to measure, but could also have direct implications for the nature of the elusive dark energy,’ said co-author Dr Axel Weiss from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn. Dark energy is thought to be responsible for the accelerated expansion of the Universe over the past few billion years, but its properties remain poorly understood because it cannot be directly observed with the currently available facilities and instruments. However, its properties influence the evolution of cosmic expansion, and hence the cooling rate of the Universe over cosmic time. Based on this experiment, the properties of dark energy remain — for now — consistent with those of Einstein’s ‘cosmological constant’. ‘That is to say, an expanding Universe in which the density of dark energy does not change,’ explained Weiss.

Having discovered one such cold water cloud in a starburst galaxy in the early Universe, the team is now setting out to find many more across the sky. Their aim is to map out the cooling of the Big Bang echo within the first 1.5 billion years of cosmic history. ‘This new technique provides important new insights into the evolution of the Universe, which are very difficult to constrain otherwise at such early epochs,’ Riechers said.

‘Our team is already following this up with NOEMA by studying the surroundings of other galaxies,’ said co-author and NOEMA project scientist Dr Roberto Neri. ‘With the expected improvements in precision from studies of larger samples of water clouds, it remains to be seen if our current, basic understanding of the expansion of the Universe holds.’

Dominik Riechers (University of Cologne) conducted the study together with his colleagues Axel Weiss (Max Planck Institute for Radio Astronomy, MPIfR), Fabian Walter (Max Planck Institute for Astronomy, MPIA), Christopher L. Carilli (National Radio Astronomy Observatory, NRAO), Pierre Cox (Institut d’Astrophysique de Paris, IAP, and Sorbonne Université), Roberto Decarli (INAF — Osservatorio di Astrofisica e Scienza dello Spazio), and Roberto Neri (Institut de RadioAstronomie Millimétrique, IRAM).

The study was funded by the US National Science Foundation, the Alexander von Humboldt Foundation, the Max Planck Society, Institut National des Sciences de l’Univers/Centre National de la Recherche Scientifique, and Instituto Geográfico Nacional.

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