Arc magazine is brought to you by the makers of New Scientist, and their first issue is out now (buy it in various physical/electronic formats from http://www.newscientist.com/arc). On the cover you'll see 'Featuring new fact and fiction from: Margaret Atwood, Stephen Baxter, M John Harrison, China Miéville, Hannu Rajaniemi, Alastair Reynolds, Adam Roberts and Bruce Sterling.' That's a polite way of saying, 'Behold! You are in the presence of some seriously heavy hitters in the Science Fiction field.' As for how to send them submissions:
The short answer is: by invitation. Arc runs off commissions, not submissions. We’re going to publish four issues this year, and we have a pretty clear idea about what we’re going to do in each of them. We’ve already been in touch with many of the authors we’d like to work with over the remainder of the year, and we’ll be in touch with the rest soon.
However, Arc magazine is open to submissions in the form of a competition closing April 8, with the theme, 'The Future Always Wins':
Arc, in collaboration with The Tomorrow Project, is looking for new, original stories – between 3000 and 5000 words – set in the near future. What do we mean by that? Near enough to be recognisable, but not so near as to be boring. Technology, in whatever guise – from robotics to synthetic biology to geoengineering – should feature prominently, but we’re looking for stories, not theses, and the human element will have to be compelling. The current theme for submissions is THE FUTURE ALWAYS WINS.
Read the full details and submit here (note: you will need a free SubMishMash account to submit): http://www.arcfinity.org/submit