That's what makes gardening so interesting. Check this article on companion planting for tomatoes (not scientific research more like a compendium of lore) https://gardening.about.com/od/totallytomatoes/qt/Tomato-Companions.htm
It gives these as good companions and gives some reasons why: Plants Recommended for Companion Planting with Tomatoes: amaranth, asparagus, basil, bean, calendula (pot marigold), carrots, celery, chive, cleome, cosmos, cucumber, garlic, lemon balm, lettuce, marigold, mint, nasturtium, onion, parsley, peas, sage, stinging nettle and sow thistle.
Then it gives things not
to plant with tomatoes and broccoli tops the list
Cabbage (Brassica) Family - All relatives of cabbage stunt the growth of tomato plants, (incl: broccoli, Brussels sprouts, cabbage, collards, cauliflower, Kale, kohlrabi, rutabaga, turnip).
I in fact have broccoli planted in the bed with tomatoes, which I have done before. It works well because the broccoli is done early. By the time the tomatoes are getting really big and taking over the bed, I can pull the broccoli. Having just recently read the above, I was considering moving my broccoli.... now I'm just confused