The phrase "are largely known" is correct and usable in written English.
It can be used when discussing information or facts that are widely recognized or accepted by a significant number of people.
Example: "The effects of climate change are largely known, yet many still underestimate its urgency."
Alternatives: "are widely recognized" or "are generally acknowledged."
The details of the deadly night are largely known.
Compare this with the historian Robert Proctor's "Cancer Wars" (1995), which bluntly states, "The causes of cancer are largely known — and have been for quite some time.
Bark beetles are largely known for their ability to undergo intermittent population eruptions that transform entire landscapes and pose significant economic hardships.
Ms. Kaplan held a colorful place in a layer of New York society made up of flamboyant, surprising and self-invented people -- she had been a suburban housewife in another life -- who are largely known for being seen.
Falk explained that the inquiry is "not so much attempting to establish facts, because these are largely known, but to use our legal background to interpret the information". It is in the interpretation of events that there is disagreement between the two sides.
Lizards are largely known to break off their tails as a defence mechanism against predators like birds that latch onto their tail.
Collective buying, as it's largely known, works by large numbers of people using their collective purchasing power to negotiate discounts from suppliers.
Although Wellcome is largely known as a biomedical organisation, we're much more than that.
It is largely known that clinical activity of a given cytotoxic agent may vary between different patients.
When I came into baseball, the Dominican was largely known still as the birthplace of major league shortstops.
Around Detroit, Mr. Ford is largely known for his work as a civic booster and charity fund-raiser.
