Super Massive Black Hole Mass Determination and. Categorization of Narrow Absorption Line Quasars Outflows

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1 1 H. James Super Massive Black Hole Mass Determination and Categorization of Narrow Absorption Line Quasars Outflows By Hodari-Sadiki James April 30 th 2012 Abstract We looked at high luminosity quasars and attempted to determine the mass of the super massive black hole at the center of each of these objects. We also examined seven of these eleven quasar spectra in order to compare them to quasars without outflows and with the presence of broad absorption line outflows. We found no correlation between the presence of outflows in our quasars and the SMBH mass, and also no correlation between our outflow quasars and the BAL quasar. Introduction: Active Galactic Nuclei(AGN) are characterized by the super massive black hole (SMBH) that usually lies at the centre of the energetic region and the also the expansive accretion disk that surrounds the SMBH and fuels these regions of relatively high luminosity (Warner 2004). The typical mass for a stellar black hole which is created from the death of a star is ~10 Msun, while a SMBH at the center of a galaxy can range from ~10 7 Msun to ~10 10 Msun. An AGN is described as the core of a galaxy with more radiating energy being emitted here than in the rest of the galaxy combined. The source of this energy is theorized to come from the large amounts of matter that is passing through the accretion disk and into the SMBH at the regions center. The accretion disk is made up of matter which is being affected by the large gravitational pull of the black hole that lies at its centre. As a result of matter from elsewhere being pulled into the black hole a huge amount of angular momentum is produced which in turn causes the formation of an energetic spiraling disc of matter. This disk usually emits energy in the ultraviolet range of wavelengths ( ) and this energy radiates from the disk via different emission lines (Warner 2004). There are two main regions of emission the broad line region (BLR) that is located closer to the accretion disk with spectral wavelengths ranging from and then a Narrow line region (NLR) that surrounds this ranging from and below (Warner). The broader emission lines are usually used by astro-physicists when looking at AGN s due to the ease of measuring their

2 2 H. James larger widths. Examples of these broad emission lines are Lyman alpha Lyα CIV (Nasa/IPAC). and carbon IV Absorption lines that can be observed in the spectra of an AGN are caused by cold gas and dust on the outskirts of the region re-absorbing the energy that has been emitted from the central powerhouse that is the accretion disk (Hamman 2004). These lines are characterized based on their width like the emission lines. AGN s are often described based on the type of absorption that are primarily detected from such objects. Broad absorption line (BAL) AGNs have very wide absorption lines while narrow absorption line (NAL) AGNs have narrow absorption lines and a lack of BALs (Simon 2010). Outflows are one of the more unique characteristics of AGN s as it is estimated that only 10% of these regions possess them (Nasa/IPAC). The outflows can be described as massive jets of energy that are emitted from the central region of the AGN. It is hypothesized that these outflows are caused by the interactions with the accretion disk s magnetic field and surrounding matter (Nasa/IPAC). Portions of the outflow jet are usually seen as being blueshifted when observed from earth as opposed to the entire AGN itself which are in most cases redshifted. Quasars Quasi-stellar radio sources or quasars for short are a form of AGN that is distinguished from the others in the group due great immense brightness (10 47 ergs/s) and to its location close to the edge of the universe (Shipman). Most of these objects are located more than a billion light years away from our galaxy, which gives us an insight into when they were created (Shipman). It is theorized that they mostly came into existence during the early stages of the universe which explain why these objects are so greatly redshifted with observed redshift values between z= 0.06 to z=6.31(davison RC). All the features of AGNs that were described above are featured in quasars. In this specific project the identity of the absorption line that characterizes the region will be important (BAL or NAL) as well as the presence of outflows from the quasars. The broad emission line CIV will also be integral to our data analysis another AGN property that was previously stated. Project The study that was done can be broken into two sections; 1) the determination SMBH mass for eleven quasars and 2) the comparison of seven known NAL quasars which contain outflows to BAL quasars with outflows and and quasars without outflows. In the first half of the project we used a method for black hole mass determination which assumes that the broad emission line region (BLR) is in gravitational equilibrium with the central source, so that the SMBH mass can be estimated by applying the virial theorem [ ]

3 H. James this produces the following equation for the total mass (Warner 2004). This argument and the derivation of our final equation for finding the black hole mass can be found in (Kaspi 1999).

410 Msun 44 1 3 1 10 egrs s 10 kms Where Msun is the mass of the sun and will be the units of measurement of the SMBH.

3 3 H. James this produces the following equation for the total mass (Warner 2004). This argument and the derivation of our final equation for finding the black hole mass can be found in (Kaspi 1999). The final equation that was used by us for SMBH determination is as follows: M SMBH L 1450Å FWHM CIV Msun egrs s 10 kms Where Msun is the mass of the sun and will be the units of measurement of the SMBH. In the second section of the project our NAL quasars will be compared to quasars observed and analyzed in Richards 2011 based on two parameters; i) the relative blueshift of the CIV line which is located in the BLR of the quasars spectrum and ii) the rest equivalent width REW of the same CIV line in the BLR. Data The data was acquired from the Sloan Digital Sky Survey SDSS and contained the spectra of twelve different quasars in the form of Flexible Image Transport System (fits) files. The data had already been reduced and the files contained information in their header about the relative redshift as well as units of the Flux (ergs/sec/cm 2 / ). Analysis of Data: SMBH Mass determination: As noted before equation 1 was used to determine the different masses of the SMBH at the center of eleven out of the twelve quasars that were in the data set. One of the spectra proved to be quite noisy with the presence of absorption lines in the CIV emission line (see fig 1 below), therefore the FWHM of the line could not be ascertained correctly and therefore had to be abandoned for both sections of the project. Figure 1. Showing the spectra taken from quasar (left) and quasar (right) with the location of the CIV magnified to show the difficulty in measure the center of some spectra.

4 4 H. James M SMBH L 1450Å FWHM CIV Msun egrs s 10 kms Equation 1. In equation 1 there were two terms that required the data from the spectra in the fits files. The first L was the 1450 Å which is the luminosity of the of spectra in the rest frame at that specific wavelength 1450 Å for the quasar being examined. This was achieved by taking the flux at the wavelength that corresponded to 1450 Å in the observed frame. The observed frame wavelength was found by using the redshift equation shown below. observed theoretical theoretical Equation 2 The value of z is the redshift that was garnered for the spectra files spectra from SDSS and ranged from ~1.9 to 4.4 for the entire data set. The flux at the observed wavelength had to be converted to units of luminosity which corresponded with the egrss 1 term that is listed in equation 1. The units of flux in fits files were ergs/sec/cm 2 /. First to correct for the per wavelength the flux is multiplied by 1450 as shown in equation 1. The per cm 2 was then corrected using the following conversion equation. Where Equation 3 is the luminosity distance of the quasar which was found by using a cosmological calculator (Ned Wright). The resulting luminosity value was in the correct units of ergs/s and used in the SMBH equation. The other factor in this equation that needed to be determined was the full width half max (FWHM) of the CIV line. The FWHM is the width of the spectral line that is being observed at half its maximum vertical height above the continuum. The measurement was taken from 1549 Å which as stated before is the rest frame wavelength of the CIV line. Corrections for redshift were again done via the use of equation 2 and all FWHM measurements made in the observed frame. The widths were taken in units of distance (Å) but then had to be converted into units of velocity (km/s) to match the constant km s that is present in equation 1. This conversion from distance to velocity was done by again using the z of the spectra and a modified version of equation 2. FWHM (Å) z theoretical Equation 4.

5 5 H. James The resulting z value for the CIV line was then used to find a velocity value using the non-relativistic equation v z c Equation 5. Where c is the speed of light in km/s. This method yielded values that could be used directly in the equation 1 to find values for SMBH mass in terms of the mass of the sun (Msun). Comparison of Outflow Quasars All twelve quasars that were present in the data set that was received from Sloan Sky Survey had been previously determined to be NAL regions via the meticulous work of Dr. Leah Simon in her work at University of Florida. Half of these regions were also found to contain outflows previously (file names shown in the table below). Quasar with Outflows Quasars No Outflows Table 1. Showing the quasars that had outflows present and those without any quasar presence. The question that is asked in this section of the project is to compare these quasars with others that have already been analyzed in the Richards 2011 and shown in the diagram below. The means of this comparison will be the relative blueshift of the CIV line and the rest equivalent width of this same line that is located in the BLR. Figure 2. Showing the Quasar outflow diagram taken from Richards 2011.

6 6 H. James Blueshift calculations Blueshift of the CIV line was determined by taking the central wavelength of this spectral line (~1549 A in the rest frame) in the observed frame using equation 2 to first estimate this wavelength along with the Z of the specific spectra file. Once the CIV line was confirmed then the central wavelength was found manually using the h parameter in IRAF. This wavelength value was then used to find the Z of the CIV line specifically with 1549 A being used as the theoretical wavelength. Equation 6. Equation 6 (relativistic redshift equation) shown above was then used to find the blueshift of the CIV line in units of velocity km/s after some simplification. The process by which the REW was found involved the use of equation 7 which is a modification of equation 2 for a wavelength range which the equivalent width is. Equation 7 The equivalent width EW of the CIV line was measured in the observed frame using the e parameter in IRAF. The resulting value for the REW can be left in a measurement of distance. Having found these two parameters in units that match the one s of the Richards paper diagram (i.e. Blueshift km/s and REW in Å) we are able to plot or seven data points on figure 2. Presentation of Results : SMBH Mass Quasar Mass Of Black Hole (in M Units) E E E E E E E * 1.39E * 1.48E * 2.69E * 1.05E+10 Table 2 shows the masses calculated for the SMBH that are presumed to be at the center of these quasars. The mass is in units of Msun. *Quasars without outflows.

7 H. James Quasar Blueshift of CIV line in km/s log of REW (A) 0434-099 755.25 1.53 0940-085 -1024.99 1.40 1426-041 961.31 1.28 1451-605 475.16 1.34 1597-040 1086.52 1.42 0272-268* 1506.64 1.

7 7 H. James Quasar Blueshift of CIV line in km/s log of REW (A) * * Table 3. Showing the Blueshift of the CIV line for the quasar and the log of the REW. Quasar regions without outflows. Quasar regions with outflows. Figure 3. Showing the Blueshift of the CIV line for the quasar and the log of the REW from table 3 plotted on the Richards 2011 diagram.

8 8 H. James Interpretation of Presented Data: The first section of the two pronged project has its results displayed in Table 2, this table shows the different quasar regions and the SMBH mass that was determined through the process explained in the second section of this paper. The general SMBH mass for previously analyzed quasars is on the order of (Davison RC). Looking at table 2 we can see that our black hole masses are in this same range with a few of them an order of magnitude greater than the generally expected results. There was also no correlation between the mass of the SMBH and their location in a region with outflows or in a region without outflows. The four quasars that are marked with an asterisk in table 2 indicate those without outflows and their SMBH masses show no real significant difference from those that are unmarked. In the second section of the project which looks at the comparison of the seven quasars that we were able to use (5 with outflows and 2 without) with the Richards diagram which is shown above unedited in figure 2 and edited in figure 3. We saw again no distinguishing factors between the locations of the two different types of quasars. For the most part they were all randomly scattered on the figure and due to their small numbers no definite conclusion could be drawn. Prior to this result we had expected the majority of the NAL quasars with outflows to be located in the region that represented quasars without outflows and not with the BAL outflow quasars. This is because the quasars with broader absorption lines usually have more matter which is being accelerated at a wider range of velocities. This usually correlates to a greater blueshift for these regions. The NAL are usually more organized systems with less disturbances which we theorized would be more similar when plot on the graph to regions without any outflows. The discussion of error is important to both parts of this project, in the SMBH determination section it must be emphasized that those values presented are estimates of the actual value of the black hole. Due to time constraints on this project we were unable to carry out proper error analysis but can easily infer the possible sources of error. The measurement of the FWHM of the CIV line from the data hampered in some of the spectra by severe noise shown in figure 1. The measurement of the luminosity at 1450 Å in the rest frame also had possible sources of error during the conversion from Flux units. One of the biggest weaknesses is the calculation of the luminosity distance DL using the cosmological calculator as a lot of the parameters were taken as is and not changed in the interest of time. Despite these possible sources of error the estimation of SMBH mass is still within the range of what it is expected to be for such luminous regions. The second section had possible uncertainties coming from locating the center of the CIV line accurately due to noise and the presence of absorption lines being present in the CIV emission line which had to be corrected for using different smoothening techniques within IRAF. There is a comparison given in figure 1 of a good spectrum as opposed to one with more abnormalities, it can be

9 9 H. James seen how difficult it was to confirm the center using of such spectra using any of the IRAF parameters. Conclusion: With the analysis of the data complete we can infer that there was no significant difference between the black hole mass of quasar regions which contained outflows and those which did not (see table 2). We can also infer that the errors, if any, that exists in the calculation of these SMBH masses are not grave as all eleven masses were in the acceptable range of black holes that have been measured in other quasar regions. The second section also showed no definite distinction between regions with outflows and regions without. As the data points for the quasar regions showed no distinctive pattern when overlaid on the Richards 2011 diagram (see figure 3)

10 10 H. James References: Richards G. T. et al. 2010, ApJS, 141, 167 Simon L.E.et al. 2010,, MNRAS 407, Simon L.E., 2010,, MNRAS Kaspi, S., et al. 1996b, ApJ, 553, 631. Blandford, R. D., & Payne, D. G. 1982, MNRAS, 199, 883 Antonucci, R. 1984, Astron J. 1993, 31: 226. Warner, C., Hamann, F., & Dietrich, M. ApJ. 2004, 608:136. Hamann F. Intrinsic AGN Absorption Lines. "An Introduction to Active Galactic Nuclei." NASA/IPAC Extragalactic Database. Web. 28 Apr < SeaSky.org. "Quasars." - Celestial Objects on Sea and Sky. Web. 28 Apr < Shipman, Harry L. Black Holes, Quasars, and the Universe. Boston, [MA: Houghton Mifflin, Print. Wright, Ned. Ned Wright's Javascript Cosmology Calculator. Web. 30 Apr < Davison RC. "Quasars." Web. 27 Apr <

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