OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY R.Birdsall, N.Ballering, A.Beardsley, L.Hunt, R.Wilson, S.Stanimi 1. Abstract The Zone of Avoidance is a relatively unknown region of space that lies on the other side of our galactic disk. Previous observations made by other collaborators such as Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and MIPS Galactic Plane Survey (MIPSGAL) which surveyed the Zone of Avoidance in the infrared spectrum with the Spitzer Space Telescope.[1] Our team decided to focus on target objects observed by the (GLIMPSE) and(MIPSGAL). These two collaborations identified twenty five new objects in the Infrared Spectrum that had the properties of galaxy like objects. For that reason, we used the Arecibo Radio Observatory in the hopes of detecting the radio signal of neutral hydrogen and identifying these objects. This piece focuses on SP192404+1456 2. Zone of Avoidance The Zone of Avoidance is a interesting region of the night sky because very little is known about what occupies that space. The ZOA is the region of the sky that lies beyond in the direction of the Milky Way galactic center. Thus EM radiation sources from the ZOA must make its way through the galactic disk. This makes detection of these galaxies difficult to near impossible. Both GLIMPSE and MIPSGAL where able to detect twenty-five obscure objects in the IR part of the spectrum, but where unable to verify exact source parameters. 1 2 OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY [2] In Figure 1. we see a spacial map of previous galactic survey's. In this figure the Zone of Avoidance can clearly be shown. The figure also shows the vast amount of space that is unknown and undocumented by Astronomers. 3. Observations and Procedure Our first observation session was on October 16 in which we chose two standard can- dle galaxies in order to test our telescope configuration and two of the Spitzer galaxies. Because of our scheduled observation time, only certain galaxies where in our area of detec- tion so we chose UGC10721 and UGC191050 for our standard candles and SP191050+1134 and SP192404+1456 for our unknown targets. We made our observations remotely using position switching (ON/OFF) with Arecibo's L-wide receiver. For SP192404+1456 we pro- duced three scans with 2 minutes on source and 2 minutes off source, 10 seconds calibration on and 10 seconds calibration off. We observed lines in 1420MHz HI line and 1665 MHz, 1667 MHz, and 1720MHz OH lines. Our beam width was set to 12.5 MHz while using 2048 frequency bins and giving us a 6.10 KHz resolution. Our last session of observing we used Arecibon L-Band Feed Array (ALFA) and increased the beam width from 12.5 to 25 MHz, however due to technical difficulties, few observations were made. OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY 3 4. UGC11362 HI Spcectrum The first step that need to be done was to select specific detector settings and calibrate the radio telescope before we started viewing our selected sources. So we choose a couple of well observed and documented galactic sources that were not located in the Zone of Avoidance. Our calibration galaxy or standard candle was UGC11362. UGC11362 is a well known double-horned galaxy in we used to test our set up of the telescope. We used the L-wide receiver for both UGC and SPITZER galaxies and below are the HI and OH lines for UGC11362. For more information on the parameter of this galaxy please see Nick Ballering's paper. http://www.icecube.wisc.edu/ rbirdsall/ Figure 2. shows the HI and OH spectrum lines for UGC11362. We see right away from the HI spectrum the distinctive double-horned profile of UGC11362. 5. SPITZER192404+145632 Spectrum From our first observing session we were able to detect SP192404+1456 in spacial coor- h m s ◦ 0 00 dinates αJ2000 = 19 24 05 right assention and δJ2000 = 14 56 32 . Below are the Radio Intensity vs. Velocity spectrum for HI and OH lines. During observing time interference from GPS satellite signal caused saturation in one of the two polarization's, because of this the figures below were created with only one polarization. Each data file was reduced with Polynomial fit functions and smoothed out with a 10 pixel smoothing function. 4 OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY Figure 3. HI emission spectrum of one polarization of target galaxy SPITZER192404+145632. This scan was made using Arecibo with 4-minutes of integration time. We can see a distinct peak around 5800 kms−1 which we believe is a distinctive feature that SPITZER192404+145632 is a spiral galaxy. Figure 4. This Figure shows the 1665 MHz OH line of SPITZER192404+145632. As can be seen the saturation interference is prevalent. We do see a little peak around 5000 kms−1 but since it is so close to interference we can not be sure if it is a source. OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY 5 Figure 5.This Figure shows the 1667 MHz OH line of SPITZER192404+145632. Figure 6. In Figures 4. shows the 1720 MHz OH line of SPITZER192404+145632. 6 OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY Figure 5. In this figure we focus on the velocity region around 5200 km s−1-5350 km s−1 were we see some small structure. Because of its gaussian however more observing is need to confirm. 6. Analysis of Spectrum During our observation sessions we were able to produce a HI spectrum with interesting features and a likely galactic source. From this spectra we are able to calculate parameter measurements of this galaxy. Using Figure 3. above, we are able to determine the systemic velocity Vsym, relative distance D, rotational velocity Vrot, total HI mass MHI , and dynamical mass Mdyn of SPITZER192404+145632. The systemic velocity is found by the equation below. Vsym= Midpoint Velocity of Spectrum −1 (1) Vsym = 5800 km= s From this result we are able to compute the relative distance of SPITZER192404+145632 by incorporating Hubble's Law. (2) V = H0 ∗ DVsym = H0 ∗ D where (3) H0 = 75km=sec=Mpc V (4) D = sym H0 (5) D = 77:33Mpc Also from Vsym we can approximate the red-shift from the equation bellow. V (6) z ≈ sym c −1 6 −1 where Vsym=5800 km*s and c = 3 ∗ 10 km ∗ s (7) z = 0:01933 The systemic velocity agrees with this red-shift and is close to what Marleau calculated for SPITZER192404+145632 in the IR which was z ≈ 0:016 The HI mass of SPITZER192404+145632 is determined by integrating the spectrum via the relation: Z 5 2 9 (8) MHI = 2:36 ∗ 10 ∗ D ∗ F (v)dv = 1:009 ∗ 10 M OBSERVATIONS IN THE ZONE OF AVOIDANCE USING ARECIBO OBSERVATORY 7 −1 where MHI is in solar masses, D in Mpc, F in Jy, and v in km*s . Finally we can esti- mate the dynamical mass of SPITZER192404+145632. We do this by using the following relation: 5 2 (9) Mdym = 2:33 ∗ 10 ∗ Vrot ∗ Rop 1 −1 where Vrot = 2 ∆v, and where ∆v is velocity width which is equal to 153 km∗s , and Rop = radius of galaxy as estimated off of Marleau et al .[1] The rotational velocity is read off −1 of the spectrum in Figure 1. as half of the full width have maximum: Vrot = 76:5km ∗ s . The radius is approximated from Table 1. in Marleau et al.[1] Using this angle and of the relative distance in Eq(3) we find Rop ≈ 28:8kpc.[1] From this estimate we can now find Mdym. We find: 11 (10) Mdym = 3:927 ∗ 10 M 7. Conclusions From the HI spectrum giving in Figure 1. and from these simple estimates we can confirm the detection of SPITZER192404+145632 in the radio spectrum. We are also able to make reasonable comparisons with Marleau et al thus confirming and possibly correcting parameters for SPITZER192404+145632. We determined that SPITZER192404+145632 9 has a neutral hydrogen mass of 1:009 ∗ 10 M . Because of the short amount of observing time we had on source we can not be sure of our number, however, the HI spectrum looks encouraging for such a short amount of integration time. The red-shift we measured, z = 0:01933, which differs from the red-shift measured using the Spritzer Space Telescope, z = 0:016. Because the Spritzer red-shift was made in the IR their uncertainties are high, so the discrepancy is to be expected. The final conclusion is that we have a object of interest in which we need more obser- vation time on the source. However, this does confirm that the use of radio astronomy in this region of space is highly advantages. With more observing time we should be able to parameters this galaxy with even more precision. 8. References [1] Marleau F.R. et al. 2008, ApJ, 136, 662 [2] Renee C. Kraan-Korteweg1 and Sebastian Juraszek2,3 Publ. Astron. Soc. Aust., 2000, 17, 6 12.