Observations of Anomalous Microwave Emission from HII Regions

Table 1

Summary of observations of AME from HII regions. The entries are listed according to their approximate detection significance, 𝜎_AME. The angular sizes are approximate or refer to the telescope beam. 𝐸 is the AME emissivity relative to 100 μm, in units μK/(MJy/sr).

Source(s)	Experiment	𝜈 [GHz]	𝜃 [′]	𝜎AME	𝐸	Reference(s)	Notes
G159.6−18.5	Various	10–60	60	17	17.8^±0.3	[4, 7]	Perseus MC. Low free-free
RCW175	CBI/VSA	31	10	7.9	5.5^±0.7	[8, 9]	2 components
G173.6+2.8	Planck	30–70	60	6.4	10.0^±3.4	[4]	Contains S235
9 northern HII	VSA	33	∼15	5.4	3.9^±0.8	[10]	Mean
G107.1+5.2	Planck	30–70	60	4.8	11.3^±4.8	[4]	Contains S140
RCW49	CBI	31	8	3.3	13.6^±4.2	[11]	G284.3−0.3
6 southern HII	CBI	31	∼5–10	1.9	3.3^±1.7	[11]	Mean includes RCW49
W40	WMAP/CBI	31–33	60/8	5*	<0.2^𝑎	[12]	*No excess detected by [13]
LPH96 201.6+1.6	GBT/CBI	5–30	∼10	10*	5.8^±2.3	[14, 15]	*Spurious; AME <24 % [15]
16 compact HII	AMI	15	<1	∼0	<5	[16]	Upper limits only

𝑎Emissivity for W40 esimate is based on a 100 𝜇m flux density of 10⁵ Jy and a 2𝜎 upper limit at 33 GHz of 5 Jy.